Pretreatment of the textile dye wastewater was accomplished using reducing agents. The reducing agents studied were sodium hydrosulfite, thiourea dioxide, and sodium borohydride. Preliminary tests were conducted using just the reducing agents. Although there was color reduction, the reduced wastewater was inhibitory to biological degradation. Additional tests were conducted with sodium hydrosulfite. These included reductions followed by pH adjustment, nutrient addition, pH adjustment and nutrient addition, and lime addition. These tests were also successful in reducing the color but were not biologically degradable. Reduction of the dye wastewater followed by oxidation, however, provided positive results (color reduction and biodegradation). A series of reduction/oxidation experiments on the textile wastewater were performed: treatment of 17 percent, 33 percent, 67 percent, and 100 percent of the textile wastewater stream. The wastewater is composed of 75 percent textile and 25 percent municipal wastewater. For the 17, 33, and 67 percent of the textile wastewater pretreated with reduction/oxidation, untreated textile and municipal wastewater were added before transfer into sequencing batch reactors for biological treatment. For the 100 percent textile wastewater stream, the initial, untreated parameters were: 2650 American Dye Manufactures Institute (ADMI) color; 780 mg/L COD; 211 mg/L TOC; and 182 mg/L BOD. The reduction/oxidation pretreatment followed by biological treatment resulted in effluent values of 615 ADMI color (77 percent reduction), 310 mg/L COD (60 percent reduction), 82 mg/L TOC (61 percent reduction), and 62 mg/L BOD (66 percent reduction). / Master of Science

by Chung Ho Yan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 127-141). / Text in English; abstracts in English and Chinese. / by Chung Ho Yan. / Acknowledgments --- p.i / Abstract --- p.ii / Table of Contents --- p.v / List of Figures --- p.xi / List of Plates --- p.xiv / List of Tables --- p.xv / Chapter 1. --- INTRODUCTION --- p.1 / Chapter 1.1 --- Textile-Dyeing Industry in Hong Kong --- p.1 / Chapter 1.2 --- Processes Involved in Dyeing Industry --- p.3 / Chapter 1.2.1 --- Desizing --- p.3 / Chapter 1.2.2 --- Scouring --- p.3 / Chapter 1.2.3 --- Bleaching --- p.3 / Chapter 1.2.4 --- Mercerizing --- p.4 / Chapter 1.2.5 --- Dyeing and Printing --- p.4 / Chapter 1.2.6 --- Finishing --- p.4 / Chapter 1.3 --- Characterization of Wastewater of Dyeing Industry --- p.5 / Chapter 1.4 --- Toxicity of Effluent from Textile-Dyeing Industry --- p.9 / Chapter 1.5 --- Related Environmental Legislation --- p.9 / Chapter 1.6 --- Chemical Specific Approach and Toxicity Based Approach --- p.11 / Chapter 1.7 --- Whole-Effluent Toxicity (WET) Test --- p.13 / Chapter 1.8 --- Toxicity Identification Evaluation --- p.14 / Chapter 1.8.1 --- Phase I - Toxicity Characterization --- p.15 / Chapter 1.8.2 --- Phase II - Toxicity Identification --- p.15 / Chapter 1.8.3 --- Phase III - Toxicity Confirmation --- p.18 / Chapter 1.9 --- Toxicity Identification Evaluation on Effluent from Textile-Dyeing Industry --- p.19 / Chapter 1.10 --- Organisms Used for Toxicity Identification Evaluation --- p.20 / Chapter 1.11 --- Selection of Organisms for Bioassays --- p.20 / Chapter 2. --- OBJECTIVES --- p.24 / Chapter 3. --- MATERIALS AND METHODS --- p.25 / Chapter 3.1 --- Sources of Samples --- p.25 / Chapter 3.2 --- Whole Effluent Toxicity Test - Baseline Toxicity Test --- p.28 / Chapter 3.2.1 --- Microtox® test --- p.28 / Chapter 3.2.2 --- "Survival test of the marine amphipod, Hyale crassicornis" --- p.29 / Chapter 3.2.3 --- "Survival test of the brine shrimp, Artemia franciscana" --- p.33 / Chapter 3.2.4 --- "Survival test of the freshwater water flea, Daphnia magna" --- p.36 / Chapter 3.3 --- Toxicity Identification Evaluation ´ؤ Phase I Toxicity Characterization --- p.40 / Chapter 3.3.1 --- pH adjustment filtration test --- p.41 / Chapter 3.3.2 --- pH adjustment aeration test --- p.42 / Chapter 3.3.3 --- pH adjustment cation exchange test --- p.43 / Chapter 3.3.4 --- pH adjustment anion exchange test --- p.44 / Chapter 3.3.5 --- pH adjustment C18 solid phase extraction (C18 SPE) test --- p.45 / Chapter 3.3.6 --- pH adjustment XAD-2 solid phase extraction (XAD-2 SPE) test --- p.46 / Chapter 3.4 --- Toxicity Identification Evaluation - Phase II Toxicity Identification --- p.47 / Chapter 3.4.1 --- Determination of anions --- p.48 / Chapter 3.5 --- Toxicity Identification Evaluation ´ؤ Phase III Toxicity Confirmation --- p.50 / Chapter 3.5.1 --- Mase balance test --- p.50 / Chapter 3.5.2 --- Spiking test --- p.51 / Chapter 4. --- RESULTS --- p.52 / Chapter 4.1 --- Characteristics of Samples --- p.52 / Chapter 4.2 --- Whole Effluent Toxicity Test - Baseline Toxicity Test --- p.52 / Chapter 4.2.1 --- Toxicity of effluent sample determined by the Microtox® test --- p.52 / Chapter 4.2.2 --- Toxicity of effluent samples determined by Hyale crassicornis survival test --- p.52 / Chapter 4.2.3 --- Toxicity of effluent samples determined by Artemia franciscana survival test --- p.57 / Chapter 4.2.4 --- Toxicity of effluent samples determined by Daphnia magna survival test --- p.51 / Chapter 4.3 --- Toxicity Identification Evaluation - Phase I Toxicity Characterization --- p.57 / Chapter 4.3.1 --- Toxicity characterization of effluent samples determined by Hyale crassicornis survival test --- p.60 / Chapter 4.3.2 --- Toxicity characterization of effluent samples determined by Artemia franciscana survival test --- p.68 / Chapter 4.3.3 --- Toxicity characterization of effluent samples determined by Daphnia magna survival test --- p.68 / Chapter 4.4 --- Toxicity Identification Evaluation ´ؤ Phase II Toxicity Identification --- p.72 / Chapter 4.4.1 --- Baseline anion concentrations in effluent samples --- p.75 / Chapter 4.4.2 --- Sample1 --- p.75 / Chapter 4.4.3 --- Sample2 --- p.75 / Chapter 4.4.4 --- Sample3 --- p.75 / Chapter 4.4.5 --- Sample4 --- p.81 / Chapter 4.4.6 --- Sample5 --- p.81 / Chapter 4.4.7 --- Sample6 --- p.81 / Chapter 4.5 --- Toxicity Identification Evaluation 一 Phase III Toxicity Confirmation --- p.85 / Chapter 4.5.1 --- Mass balance test results --- p.85 / Chapter 4.5.2 --- Spiking test results --- p.96 / Chapter 5. --- DISCUSSION --- p.102 / Chapter 5.1 --- Whole Effluent Toxicity Test ´ؤ Baseline Toxicity Test --- p.102 / Chapter 5.1.1 --- Toxicity of effluent sample determined by the Microtox® test --- p.102 / Chapter 5.1.2 --- Toxicity of effluent samples determined by Hyale crassicornis survival test --- p.103 / Chapter 5.1.3 --- Toxicity of effluent samples determined by Artemia franciscana survival test --- p.104 / Chapter 5.1.4 --- Toxicity of effluent samples determined by Daphnia magna survival test --- p.104 / Chapter 5.2 --- Toxicity Identification Evaluation ´ؤ Phase I Toxicity Characterization --- p.105 / Chapter 5.2.1 --- pH adjustment filtration test --- p.105 / Chapter 5.2.2 --- pH adjustment aeration test --- p.106 / Chapter 5.2.3 --- pH adjustment cation exchange test --- p.106 / Chapter 5.2.4 --- pH adjustment anion exchange test --- p.106 / Chapter 5.2.5 --- pH adjustment C18 solid phase extraction (C18 SPE) test --- p.107 / Chapter 5.2.6 --- pH adjustment XAD-2 solid phase extraction (XAD-2 SPE) test --- p.107 / Chapter 5.3 --- Toxicity Identification Evaluation - Phase II Toxicity Identification --- p.107 / Chapter 5.3.1 --- Efficiency on chemical reduction of pH adjustment filtration test --- p.109 / Chapter 5.3.2 --- Efficiency on chemical reduction of pH adjustment aeration test --- p.109 / Chapter 5.3.3 --- Efficiency on chemical reduction of pH adjustment cation exchange test --- p.109 / Chapter 5.3.4 --- Efficiency on chemical reduction of pH adjustment anion exchange test --- p.109 / Chapter 5.3.5 --- Efficiency on chemical reduction of pH adjustment CI8 SPE test --- p.109 / Chapter 5.3.6 --- Efficiency on chemical reduction of pH adjustment XAD-2 SPE test --- p.110 / Chapter 5.4 --- Toxicity Identification Evaluation - Phase III Toxicity Confirmation --- p.110 / Chapter 5.4.1 --- Mass balance test results --- p.110 / Chapter 5.4.2 --- Spiking test results --- p.114 / Chapter 5.5 --- Comparison of Toxicant(s) Identified in the Six Dyeing Industrial Effluents --- p.117 / Chapter 5.6 --- Toxicant(s) Identified in Textile-Dyeing Industrial Effluent --- p.119 / Chapter 5.7 --- "Sources, Fate and Treatment of Sulfite Ion" --- p.120 / Chapter 5.8 --- Toxicity of Sulfite Ion --- p.121 / Chapter 5.9 --- Effect of Salinity on the Toxicity of Sulfite Ion --- p.122 / Chapter 5.10 --- Recommendation --- p.123 / Chapter 6. --- CONCLUSIONS / Chapter 7. --- REFERENCES / Chapter 8. --- APPENDICES

Consumer demands have led to the development of new, more stable textile dyes. These dyes, many of the azo type, are often incompletely degraded/removed in wastewater treatment plants, leading to the discharge of highly colored effluents to rivers and streams. Concerns by downstream users of that water have led to enactment of effluent color and toxicity standards for plants that treat textile dye wastewater. Both anaerobic and aerobic biological degradation of azo dyes have been reported in the literature; the rate and extent of degradation is often quite dye-specific. This research utilized laboratory-scale reactors to investigate the effectiveness of those treatments, both singly and in combination, on two azo dye wastewaters: a textile dyeing and finishing process water and a municipal wastewater consisting predominately of textile dyeing and finishing mill effluents. / Master of Science

A reactive-ionic functional group was incorporated into the structure of fiber finishes and colorants to provide high-yield add-on and permanency. The reactive-ionic group consists of a moderately strained, cyclic ammonium group which undergoes ionic assembly on the surface of negatively charged substrates. The ionic bond is then converted to a covalent bond at elevated temperatures via a ring-opening reaction. A reactive-ionic alkyl (wax) finish was prepared from octadecanol and N-phenyl pyrrolidine then applied to a glass slide to provide a permanent, hydrophobic surface with an average contact angle increase of approximately 40°. A reactive-ionic fluorinated finish was prepared from 1H,1H,2H,2H-perfluoro-1-octanol and N-phenyl pyrrolidine and after application served as a permanent, non-wetting, anti-stain finish for nylon carpet. A reactive-ionic chromophore (dye) was prepared from C.I. Disperse Red 1 and quinuclidine. The reactive-ionic dye was applied to cellophane and nylon films and bleached cotton, nylon and silk fabrics. The percent exhaustion for a 1% owf dyeing of silk fabric was measured to be 98% using visible light absorbance spectrophotometry. K/S values obtained from reflectance spectrophotometric measurements of a 1% owf dyeing of nylon 6,6 fabric showed a 6% color loss after solvent extraction, indicating that the dyeing was indeed permanent.

Orientador: João Sinezio de Carvalho Campos / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-10T13:40:00Z (GMT). No. of bitstreams: 1 Giordano_JoaoBatista_D.pdf: 4390680 bytes, checksum: 205aa7153da8e4745f9366e58adcb8cf (MD5) Previous issue date: 2007 / Resumo: Dentre as técnicas de modificação de superfícies aplicadas na indústria para melhorar adesão, o tratamento por descarga corona é amplamente utilizado. Durante o tratamento por descarga coro na, espécies ativas são geradas, as quais podem reagir com a superfície do polímero ocasionando quebra de cadeias e formação de radicais, criando assim grupos polares na superfície e conseqüentemente, aumentando a sua energia superficial e propriedade de adesão. Neste trabalho utilizaram-se tecidos de poliéster e de algodão. Nos processos convencionais de preparação de tecidos são usados agentes químicos que agridem os efluentes têxteis, assim a descarga corona propõe-se como tratamento prévio do material sem ação de tais agentes, sendo tratamento único e apenas físico. Os objetivos deste trabalho são: 1. Tratar com descarga corona tecidos de poliéster e tecidos de algodão (engomado, lavado e desengomado); 2. Verificar hidrofilidade e absorção de corantes em tecidos de algodão tratados com descarga corona; 3. Verificar propriedades mecânicas em tecidos tratados com descarga corona. 4. Verificar a adesão de pigmentos em de tecidos de poliéster tratados com corona. Tecidos foram submetidos à descarga: corona variando-se o tempo exposição e altura entre os eletrodos, em seguida foi realizada testes de hídrofilidade, absorção de corante tipo reativo, adesão de pigmentos, solidez a lavagem e ensaios de resistência à tração e alongamento. Foi utilizada a técnica de microscopia óptica, ensaio de hidrofilidade para caracterizar os efeitos causados. Os resultados mostram que: houve aumento da hidrofilidade do tecido de algodão que de 50% em amostra sem tratamento passou até a 280% com o tratamento, observou-se também que com te~pos de 1 mino já ocorrem modificações nos tecidos quanto a hidrofilidade e absorção de corantes; houve aumento da absorção de corante nas regiões tratadas principalmente em processos contínuos de tingimento; ocorreu boa aderência de pigmentos em tecidos de poliéster tratados; não ocorrem alteração das propriedades mecânicas (resistência a tração e alongamento) nas amostras tratadas. / Abstract: Amongst the techniques of modification of surfaces applied in the industry to improve adhesion, the treatment for discharge corona widely is used. During the treatment for discharge corona, active species are generated, which can consequently react with the surface of polymer causing chain in addition and formation of radicals, thus creating polar groups in the surface and, increasing its superficial energy and property of adhesion. In this work they had been used weaveed of polyester and cotton. In the conventional processes of fabric preparation they are used chemical agents whom the effluent textile attack, thus the discharge corona is considered as previous treatment of the material without action of such agents, being treatment only e only physicist. The objectives of this work are: 1.To deal with discharge corona weaveed to polyester and fabrics cotton (starchy, washed and dissolved the gum); 2. To verify water absorption and absorption of corantes in fabrics of cotton treated with discharge corona; to 3.Verificar mechanical properties in fabrics dealt with discharge corona. 4. To verify the pigment adhesion in of treated polyester fabrics with corona. Fabrics had been submitted to the discharge corona varying the time exposition and height between the electrodes and, after that water absorption tests had been carried through, absorption of corante reactive type, pigment adhesion, solidity the laudering and assays of tensile strenght and allonge. The technique of optic microscopy was used, assay of water absorption to characterize the caused effect. The results show that: it had increase of the hidrofilidade of the cotton fabric that of 50% in sample without treatment passed until 280% with the treatment, was 9.lso observed that with times of 1 min. already the water absorption and absorption of corantes occur modifications in fabrics how much; it had increase of the absorption of corante in the regions treated mainly in continuous processes of dyeing good pigment tack occurred in treat polyester fabrics; they do not occur alteration of the mechanical properties (resistance the traction and allonge) in the treated samples. / Doutorado / Ciencia e Tecnologia de Materiais / Doutor em Engenharia Química

The National Academy of Sciences recently published a report which calls for improvements to the field of forensic science. Their report criticized many forensic disciplines for failure to establish rigorously-tested methods of comparison, and encouraged more research in these areas to establish limitations and assess error rates. This study applies chemometric and statistical methods to current and developing analytical techniques in fiber analysis. In addition to analysis of commercially available dyed textile fibers, two pairs of dyes are selected based for custom fabric dyeing on the similarities of their absorbance spectra and dye molecular structures. Visible absorption spectra for all fiber samples are collected using microspectrophotometry (MSP) and mass spectra are collected using electrospray ionization (ESI) mass spectrometry. Statistical calculations are performed using commercial software packages and software written in-house. Levels of Type I and Type II error are examined for fiber discrimination based on hypothesis testing of visible absorbance spectra using a nonparametric permutation method. This work also explores evaluation of known and questioned fiber populations based on an assessment of p-value distributions from questioned-known fiber comparisons with those of known fiber self-comparisons. Results from the hypothesis testing are compared with principal components analysis (PCA) and discriminant analysis (DA) of visible absorption spectra, as well as PCA and DA of ESI mass spectra. The sensitivity of a statistical approach will also be discussed in terms of how instrumental parameters and sampling methods may influence error rates.

M. Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology / Fenton oxidation is classified into two processes, homogeneous and heterogeneous. Homogeneous Fenton oxidation process, have been shown to be efficient in the degradation of organic pollutants. However, it was shown to have limitations which can be addressed by the heterogeneous Fenton oxidation. Despite the high efficiency of the heterogeneous Fenton oxidation process in the degradation of recalcitrant organic pollutants, the currents synthesis trends of the heterogeneous Fenton catalyst have been proven to be time and energy constraining, since it involves the multi-step were the activated carbon have to be prepared first then co-precipitate the iron oxide on the activated carbon. However, as much as the heterogeneous Fenton catalyst has been proven to have high catalytic activity towards degradation of organic pollutants, these catalysts have some limitations, such limitations include metal ions being leached from the catalyst support into the treated water causing catalyst deactivation and a secondary pollution to the treated water. In this thesis, these catalysts have been applied in the degradation of recalcitrant organic pollutants such as methylene blue and phenols. This study focuses on the single step synthesis of iron oxide nanoparticles supported on activated carbon, were carbonaceous material is impregnated with iron salt then pyrolysed via microwave heating. Microwave power and the amount of iron salt were optimized. The prepared activated carbon-iron oxide composites were applied to the degradation of 2-nitrophenol (2-NP) and methylene blue (MB). Methylene blue was used as a model compound due to the fact that it is easier to monitor the degradation process with UV-Vis as compared to 2-nitrophenol . 2-nitrophenol the additional step for the adjustment of pH is required since nitrophenols are colorless in color at lower pH. The characterization showed that the microwave power and the amount of the iron precursor have an influence on the porosity and surface functional groups of the activated carbon. Further it was vi observed that microwave power and iron precursor influnces the amount of iron oxide formed on the surface of the support. It was also observed that the activated carbon-iron oxide composite have the catalytic effects on the Fenton oxidation process of MB and 2-NP. The parameters such as H2O2, pH, catalyst dose, initial concentration, temperature affect the degradation of both MB and 2-NP. Kinetics studies showed that Fenton is a surface driven reaction since the results fitted the pseudo first order model. The thermodynamics parameters also showed that the reaction is endothermic, spontaneous and is randomized. This implies that the reaction of the degradation of MB and 2-NP is feasible and the catalysts prepared have high catalytic activity. MB and 2-NP were degraded to smaller organic molecules (carboxylic acids). The stability of the catalyst observed to decrease as the number of cycles increased, this is due to the leaching of iron ions from the support material. Hence it was concluded that the activated carbon-iron oxide composite was successfully synthesized and had the high catalytic activity for the degradation of MB and 2-NP.

PhDENV / Department of Ecology and Resource Management / Some industries such as textiles, ceramics, paper and printing are known to use significant amounts of dye to colour their products and during the colouring process, certain quantities of dyes are absorbed by the products, and some of them end up in wastewater. Depending on their application, some synthetic dyes are designed to be chemically or biologically resistant and their presence in the environment can cause severe environmental problems because of their colour impartation to water bodies. Therefore, proper treatment is required to remove these pollutants from wastewater before discharge into the environment. In this thesis, the potential of dye removal from wastewater by calcined magnesite, halloysite nanoclay and calcined magnesite - halloysite nanoclay composite was evaluated. To this end, the study was subdivided to four segments. The first segment of the study focused on evaluating the efficiency of using calcined magnesite to remove Methylene Blue (MB), Direct Red 81 (DR81), Methyl Orange (MO) and Crystal Violet (CV) dyes from aqueous systems using a batch study. To achieve that, several operational factors like residence time, adsorbent dosage, dye concentration and temperature were appraised. The adsorbent was subjected to different kinds of physicochemical characterization to determine the various characteristics that would assist in the dye uptake process. Characterization results showed that the adsorbent material was highly crystalline with magnesite, periclase, dolomite, and quartz as some of the crystalline phases. The batch study proved that calcined magnesite is effective in the treatment of dye contaminated water and moreover it performed well in terms of colour removal, though exceptional results were recorded for CV removal with complete decolourisation occurring in first few minutes of contact. In terms of experimental adsorption capacity, the performance of calcined magnesite was in the order CV (14.99 mg/g) > DR81 (12.56 mg/g) > MO (0.64 mg/g) > MB (0.39 mg/g). Mechanisms of adsorption where explained by fitting the experimental data into adsorption isotherms, kinetics, and thermodynamic parameters. Neither, the Langmuir, nor the Freundlich nor the Dubinin Radushkevich, nor the Temkin model could perfectly describe the adsorption of the four dyes onto calcined magnesite, however adsorption kinetics obeyed the pseudo second order model, implying that, the dye removal process was primarily a chemical process. In accordance with the results of this study, it can be concluded that calcined magnesite can be used effectively for the removal of dyes in aqueous solution and thus can be applied to treat wastewater containing dyes. The second segment of the study focused on the removal of MB, DR81, MO and CV dyes by halloysite nanoclay. Physicochemical characterisation revealed that the nanoclay has a surface area of 42 m²/g and its ABSTRACT iv morphology is predominated by tubular structures, which exhibit some hollow rod like structures. Various important parameters namely contact time, initial concentration of dyes, dosage, solution temperature and solution pH were optimized to achieve maximum adsorption capacity and it was observed that the effect of initial pH and temperature of the aqueous solution was neglibible on removal of the four dyes. The experimental adsorption capacities towards 40 mg/L of MB, DR81, MO and CV dyes were 17.51, 14.11, 0.38, and 4.75 mg/g respectively. The results indicate that natural halloysite nanoclay is an efficient material for the removal of the selected dyes. Due to its low cost and non-toxicity, halloysite nanoclay can be considered a good replacement option of other high cost materials used to treat coloured wastewater especially in developing countries like South Africa. Having observed the performance of calcined magnesite and halloysite nanoclay individually in the removal of selected dyes, a third study was designed with the aim of preparing a nanocomposite adsorbent from the aforementioned adsorbent materials and then evaluating the synergistic influence of the mechanochemical modification by a ball miller on the removal of MB, DR81, MO and CV dyes. Physicochemical characterization was carried out to get an insight of pre- and -post adsorption characteristics of the nanocomposite material and results showed major changes which could be an indication of dye uptake by the nanocomposite material. According to the results, the nanocomposite material outcompeted its component individual constituent materials i.e (calcined magnesite and halloysite nanoclay material) in the removal of DR81, which in turn was the highest removal efficiency observed for the whole batch adsorption study recording a maximum adsorption capacity and percentage removal of 19.89 mg/g and 99.40% respectively. Experimental results fitted the Langmuir and pseudo-second order models perfectly hence demonstrating that adsorption took place on a homogenous adsorbent layer via chemisorption. In overall, the results suggested that the nanocomposite is a suitable adsorbent for decolourising industrial wastewater. Based on the overall performance of the adsorbents in removing the four dyes, it was observed that the nanocomposite material had a high affinity for DR81 dye hence it was chosen as the model dye for further application in column studies. The effect of flow rate, bed height and initial dye concentration on the removal of DR81 was investigated. Maximum bed capacity and equilibrium dye uptake were determined and break through curves were plotted. Percentage dye removal increased with decrease in flow rate and increase in bed height. The maximum capacity of column was found to be about 51.73 mg DR81 per gram of the nanocomposite adsorbent for a flow rate of 3 mL/min, initial concentration of 10 mg/L and 4 cm bed height. Data from column studies was fitted to the Thomas model and Adams-Bohart models. The comparison of the R2 values obtained from both models showed a better fit for the nanocomposite material than the individual halloysite nanoclay and calcined magnesite materials. The study revealed the applicability of calcined magnesite- halloysite nanoclay composite in fixed bed column for the removal of DR81 dye from aqueous solution. v The reuse of an adsorbent is essential in order to make the adsorption process economic and environmentally friendly. To recover the adsorbate and renew the adsorbent for further use, a chemical method of regeneration was applied by using 0.1 M NaOH as the desorbent. Regeneration with 0.1 M NaOH proved very efficient for some dyes and less efficient for others depending on the adsorbent material used at the time. The general observation was that the adsorption capacity of the adsorbent materials decreased with successive adsorption – desorption cycles. Furthermore, regeneration with NaOH, favoured the acidic dyes (DR81 and MO) more than the basic dyes (MB and CV) possibly due to electrostatic interactions between oppositely charged molecules allowing for reversible reactions to take place. The three tested adsorbents namely calcined magnesite, halloysite nanoclay and their nanocomposite thereof were applied for the treatment of real wastewater effluent from a printing and ink industry. The adsorbents performed very well in terms of colour removal as recommended by the South African standards of wastewater discharge, However, in terms of pH, calcined magnesite and the nanocomposite produced a highly alkaline solution hence wastewater neutralisation by an acid is recommended before discharge. These findings show that the two natural clay-based materials (calcined magnesite and halloysite nanoclay) and their nanocomposite thereof have a great potential for application in dye wastewater remediation since the materials used in the process are inexpensive, abundant and require minimal modifications. / NRF

PhD (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Water is a basic resource to mankind. The environment is deteriorating daily due to industrial pollution of water resources. Industrial effluents containing organic pollutants such as dyes are undesirable even at low concentrations in the environment. Natural biomaterials have been applied as adsorbents for dye removal from water systems, however, their application has been limited by their low adsorption capacity. Much attention has been focused on the chemical modification of natural biomass via grafting processes. The modification of natural polymers by graft copolymerization is a promising technique since it functionalizes a biopolymer thus imparting desirable properties. The purpose of the study was to prepare and optimize the working conditions for the pine-magnetite bionanocomposites (PMC) as adsorbents and as photocatalysts modifiers. First, this work focuses on the synthesis and optimization of reaction variables in the preparation of PMC for the removal of methylene blue (MB). The thesis also explores the synthesis of acrylamide and acrylic acid-grafted PMC, resulting in the formation of acrylamide-grafted PMC (GACA) and acrylic acid-grafted pine-magnetite bionanocomposites (GAA), respectively. The grafting of functional groups such as –CO, –NH2 onto cellulose from acrylamides is also explored in detail. The adsorption conditions optimized were used to investigate the adsorption efficiency of GAA and GACA on MB. Finally, the application of PMC and GAA as modifiers for amorphous TiO2 and N-doped TiO2was carried out. The photocatalytic bionanocomposites from PMC (namely PMC–a-C,TiO2 and PMC–a-C,NTiO2) and those from GAA (labeled GAA–a-C,TiO2 and GAA–a-C,NTiO2) are compared by their photocatalytic efficiency on the degradative removal of an alkaline dye mixture formed from Reactive red 120 (RR 120) and Rhodamine B (Rh B). The synthesis procedure for PMC involved treating pinecone biomass with 0.15 M NaOH solution to remove unwanted plant extracts and the subsequent coating of the treated pinecone with iron oxide magnetic particles through a co-precipitation method. The variables used for the experiments were volume of NH4OH (5 to 40 cm3), reaction temperature (40 to 100 °C), effect of time (15 to 60 min) and mass (1.0 to 3.5 g). The PMC and acrylic acid grafted pine-magnetite composite (GAA) were probed for structural morphology and surface properties using various surface characterization instrumental techniques. Strong chemical interactions between pinecone magnetite and acrylic acid were demonstrated by thermogravimetric (TGA), differential thermal analysis (DTA) and X-ray photoelectron spectroscopy (XPS) for these unique bionanocomposites as such suggesting high chemical stability. Grafting acrylic acid was shown by XPS to form polyacrylic acid on the surface of the bionanocomposites and thus capping the surface groups. Significant differences in size were shown by transmission electron spectroscopy (TEM) and scanning electron microscopy (SEM); i.e., smaller particle sizes (Ave = 13.0 nm) for GAA and slightly larger for PMC (Ave = 14.0 nm). Brunauer Emmett Teller (BET) surface analysis demonstrated a larger surface area, pore volume and pore diameter (59.9 m2.g-1, 0.2254 cm3.g-1 and 28.14) for GAA compared to PMC. These characteristics coupled with the point of zero charge for GAA (pHpzc = 6.8) were critical in enhancing the efficiency of GAA adsorption of MB at pH 12 and further enable GAA to have a higher desorption efficiency of up to 99.7% after four cycles of washing with 0.10 M HCl. The adsorption kinetics and isotherm studies indicated that the adsorption process follows the pseudo second order kinetics and Langmuir isotherm respectively. The adsorbent also showed improvement in the adsorption capacity and reusability promising to be used for the removal of dyes in a prototype scale. GAA and MB adsorption mechanism was confirmed to be through intra particle diffusion. The overall performance of the GAA bionanocomposites is hinged on the formation of polyacrylic acid on the surface, its structural morphology, and the enhanced surface properties. Most importantly, the plant-based materials (lignin and cellulose) provide an environment that is rich with surface (–COOH and –OH) groups for the attachment of the magnetite nanoparticles while the polyacrylic acid stabilizes the magnetite onto the pinecone nanoparticles while reducing the point of zero charge for increased adsorption of cationic species. The photocatalytic bionanocomposites were fabricated from the adsorptive bionanocomposites using a simple solgel process in which ~10 wt.% of PMC and GAA, respectively, were used as a starting agent. Titanium butoxide was used as a precursor, acetylacetone as a dispersant and ethylene diamine as a nitrogen source. Using this procedure, amorphous carbon-doped titania (a-C,TiO2) and amorphous carbon and nitrogen co-doped titania (a-C,NTiO2) were fabricated except that the biopolymer was not added. Two sets of amorphous titania bionanocomposites were fabricated. One set was the nitrogen doped forms that had been modified with PMC and GAA (PMC–a-C,TiO2 and GAA–a-C,NTiO2). The other set of photocatalytic bionanocomposites produced in this work were without nitrogen (PMC–a-C,TiO2 and GAA–a-C,TiO2). TEM and SEM micrographs showed that all the photocatalysts consisted of globular, smooth aggregates of nanosized a-CTiO2 and a-C,NTiO2 which decreased in size with N-doping and the incorporation of GAA and PMC to as low as <30 nm. Surface chemical analysis through FTIR, XPS and EDS confirmed the presence of C, O, Ti and N (for the N-doped photocatalysts). In addition, it was demonstrated that N-doping into TiO2 had taken place, albeit with most of the N incorporated as organic nitrogen. It was further demonstrated that because of the absence of high temperature calcination, the process chemicals played a significant role in doping the photocatalysts with carbon resulting in the promotion of photocatalytic activity for a-C,TiO2 to the point of surpassing that of, a-C,NTiO2 and all the PMC-modified photocatalytic bionanocomposites. a-C,TiO2 had an overall 94% removal of the dyes, Rhodamine B (RhB) and Reactive red 120(RR 120), under UV illumination. The benefit of co-doping a-TiO2 with C, N and the biopolymers was realized with the incorporation of GAA as a modifier. The result was 97% removal of the dyes by GAA–a-CTiO2 and 99% for GAA–a-C,NTiO2. It was further observed that the degradation of the binary mixture of the dyes (RhB and RR 120) proceeded through the zero order kinetics for the a-C,TiO2 based photocatalysts and first order kinetics for the N-doped photocatalysts. The work, has, therefore demonstrated the applicability of plant-based biopolymers in the fabrication of nanoadsorbents and nanophotocatalysts. While the photocatalytic degradations were carried out under UV-light, there still remains a number of possible avenues that researchers can build on to improve the visible light-driven photocatalytic bionanocomposites. The research work has proven the effectiveness of novel pinecone magnetic nanoparticle materials and TiO2-based photocatalyst for the degradation of undesirable dyes from wastewater.