Discharge of untreated industrial effluents containing heavy metals is hazardous to the environment as they are highly toxic, accumulates in the food chain and persistent in nature. Because of these adverse effects, their removal from wastewater is a substantial step in the protection of the environment and human health. Biosorption is found to be an eco-friendly, economical and lucrative separation technique in the removal of metal ions from effluent. This study explores the seperation potential of a new sorbent, fibroin (constituent of natural silk spun by Bombyx mori) for the removal of lead, chromium, copper and cobalt ions from effluent water. The biosorbent was prepared by the separation of cocoon into its constituents, fibroin and sericin. The removal of sericin from fibroin, called silk degumming, was carried out by water extraction method. Effect of temperature (55-95oC) on the kinetics and quantity of sericin removed was studied. The separation kinetics was approximated by the intraparticle diffusion model and the pseudo-second-order equation. Biosorption characteristics of fibroin for the removal of lead, chromium, copper, and cobalt ions from aqueous solution were investigated through a batch study. The effect of initial solution concentration, contact time and temperature on the sorption process was investigated. The adsorption equilibrium was described by the Langmuir isotherm. The thermodynamic parameters, the change in enthalpy (∆H) and change in entropy (∆S), were calculated by using Van’t Hoff plot. An accurate mathematical expression was used to calculate Gibbs free energy (∆G), for the adsorption of all metals on fibroin. For the kinetic data analysis, pseudo-second-order equation was modified based on the fact that the term qe in the kinetic equation should be the equilibrium uptake corresponding to the instantaneous metal concentration in the solution. In order to evaluate the rate constant k2, sorption kinetic data was fitted to the modified pseudo-second-order equation. The calculated values of rate constant k2, for the adsorption of all metals on fibroin, were used to the modified pseudo-second-order model to predict the kinetic data. A good comparison was observed between the experimental data and model calculations. The kinetic data was also fitted to the intraparticle diffusion model which showed a multi linear trend. The metal ions were desorbed from fibroin up to ten cycles of adsorption and desorption by using 0.05M ethylenediaminetetraacetic acid (EDTA). The removal of metal ions from fibroin was found to be rapid since complete desorption occurred within 15min. The uptake capacity of fibroin and adsorption/desorption kinetics remained almost the same even after ten cycles. The rate constants for both adsorption and desorption were also calculated by fitting the kinetic data to the modified pseudo-second-order model. The dynamic adsorption was studied in a flow-through column packed with fibroin for the removal of all metals. Experiments were performed in order to study the effect of influent concentration (12-75ppm), influent flow rate (0.15-0.24ml/min) and regeneration of fibroin bed (upto 4 cycles). Whereas the bed height, column diameter and amount of adsorbent packed were kept constant during this study. Fibroin bed saturated with metal ions was regenerated effectively by using 0.5M EDTA solution. After four consecutive cycles of adsorption and desorption, no change in the uptake capacity was observed. The bed depth service time model, the Thomas model and the Yoon-Nelson model were used to analyze the breakthrough data. The calculated values of Yoon-Nelson constants were used to predict the breakthrough curves. A good comparison was observed between experimental data and the Yoon-Nelson model calculations. An investigation was conducted to check if the adsorption of metal ions was carried out either by the surface of the fibroin or they were adsorbed deep inside its polymer network, and bulk was used. For this study, silk fibroin was transformed into thin films of three different thicknesses having same surface area. Batch experiments were conducted to study the thickness effect of fibroin films for the adsorption of metal ions. A constant amount of metal uptake for all three fibroin films showed that the adsorption was not a surface phenomenon, but the bulk body of the fibroin was used for this separation. Kinetic data was fitted to the modified pseudo-second-order model. The kinetic rate constant k2 was not significantly affected by the film thickness which abrogated the possibility of simple diffusion mechanism for metal sorption into fibroin. Fibroin films loaded with metal ions were desorbed once dipped in deionized water. The desorption kinetics was again described by the modified pseudo-kinetic-model. The calculated values of desorption rate constant kd were used to predict the kinetics of film desorption. A good comparison was observed between the modified pseudo-second-order model calculations and experimental desorption data of fibroin films.

No description available.

Thesis (Ph. D.)--University of Idaho, 2006. / "May 31, 2006." Includes bibliographical references (leaves 94-101). Also available online in PDF format.

Made available in DSpace on 2015-05-14T13:21:17Z (GMT). No. of bitstreams: 1 Arquivototal.pdf: 3236722 bytes, checksum: c565548ef9bd6c5867bb5994542c2bdf (MD5) Previous issue date: 2012-06-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Mesoporous organic-inorganic hybrids are promising candidates in the field of adsorption. In this work new adsorbents based on mesoporous silica MCM-41 and HMS types organofunctionalized with groups containing nitrogen and sulfur using the method after functionalization were synthesized. The HMS silica was obtained from neutral n-dodecylamine surfactant and modified with organosilanes containing one, two or three nitrogen atoms, then submitted to the functionalization reaction with mercaptoacetic acid or ethylene sulfide. The MCM-41 silica, obtained from CTAB template was modified with the organosilane containing one nitrogen atom and functionalized with carbon disulfide. The set of HMS functionalized silicas were used in the adsorption process of divalent cations Cd, Co, Cu, Ni and Pb from aqueous solution and kinetic study. All HMS and MCM-41 matrices were characterized through elemental analysis, thermogravimetry, surface area, infrared spectroscopy, nuclear magnetic resonance of 13C and 29Si and X-ray diffraction techniques. The elemental C, H, N and S analysis suggest success on the immobilization of ethylene sulfide, thioglycolic acid ligands, pointing probably to an ethylene sulfide molecules polymerization. The matrix MCM-41 showed a small degree functionalization, 0.09 mmol g -1 of sulfur anchored to the surface. HMS functionalized matrices demonstrated having adsorption capacity of Cd2+, Co2+, Cu2+, Ni2+ and Pb2+, being the best results observed for Cu2+ cation. All systems studied obey the pseudo-second order kinetics of reaction. The values of Cu2+ ions adsorbed on the matrices HMS containing one, two or three nitrogen atoms and mercaptoacetic acid were 0.86, 1.08 and 1.06 mmol g-1, respectively. For matrices containing one, two or three nitrogen atoms and ethylene sulfide, values were 0.83, 1.38 and 1.01 mmol per gram, respectively. / Híbridos mesoporosos orgânico-inorgânicos são candidatos promissores na área de adsorção. Neste trabalho, foram sintetizados novos adsorventes baseados em sílicas mesoporosas do tipo HMS e MCM-41 organofuncionalizadas com grupos contendo nitrogênio e enxofre empregando o método pós funcionalização. A sílica HMS foi obtida a partir do direcionador n-dodecilamina e modificada com os organossilanos contendo um, dois ou três átomos de nitrogênio, em seguida submetidas a reações de funcionalização com ácido tioglicólico ou etilenossulfeto. A sílica MCM-41, obtida a partir do direcionador CTAB, foi modificada apenas com o organossilano contendo um átomo de nitrogênio e funcionalizada com dissulfeto de carbono. O conjunto de sílicas HMS funcionalizadas foram aplicadas em processos de adsorção dos cátions divalentes Cd, Co, Cu, Ni e Pb em solução aquosa, sendo realizado o estudo cinético. As matrizes HMS e MCM-41 puras, modificadas e funcionalizadas foram caracterizadas através das técnicas de análise elementar, termogravimetria, determinação de área superficial, espectroscopia na região do infravermelho, ressonância magnética nuclear de 13C e 29Si e difratometria de raios-X. Os dados de análise elementar de C, H, N e S sugerem o sucesso da imobilização dos ligantes ácido tioglicólico e etilenossulfeto apontando para possível polimerização das moléculas de etilenossulfeto. A matriz MCM-41 apresentou pequeno grau de funcionalização, 0,09 mmol g-1 de enxofre ancorado à superfície. As matrizes HMS funcionalizadas demonstraram capacidade para adsorção dos cátions Cd2+, Co2+, Cu2+, Ni2+ e Pb2+, sendo os melhores resultados verificados para o cátion Cu2+. Todos os sistemas estudados obedecem à cinética de reação de pseudo-segunda ordem. As quantidades dos cátions Cu2+ fixos adsorvidos nas matrizes HMS contendo um, dois ou três átomos de nitrogênio e o ligante ácido tioglicólico foram: 0,86; 1,08 e 1,06 mmol g-1, respectivamente. Para as matrizes contendo um, dois ou três átomos de nitrogênio e o ligante etilenossulfeto os valores foram: 0,83; 1,38 e 1,01 mmol por grama, respectivamente.

This study investigated the chemical modification method by citric acid and its enhancement effect on the adsorption capacity of sugarcane bagasse (SB) for copper removal from aqueous solution. Characterization studies were performed by using Fourier transform infra red (FTIR), which showed the introduction of carboxylic group in the structure the modified sugarcane bagasse (MSB). Batch study revealed the influence of pH, time, initial concentration of metal ion on adsorption capacity. The data showed an extremely good fit to Langmuir isotherm model from which the maximum adsorption capacity estimated reached 28.17 mg/g at optimum pH 5.5. Fixed bed column study using the adsorbent MSB confirmed that the breakthrough curves of the adsorption processes were dependent on bed height, initial concentration and flow rate. Linear regression analysis of the data demonstrated that Yoon-Nelson kinetic models were appropriate to explain the breakthrough curves. / Nghiên cứu đã thực hiện biến tính hóa học vật liệu bã mía bằng acid citric và đánh giá khả năng hấp phụ ion Cu(II) trong nước của bã mía (SB) trước và sau biến tính axit citric. Khảo sát cấu trúc vật liệu thông qua phổ hồng ngoại FTIR cho thấy các nhóm chức carboxylic có khả năng hấp phụ kim loại xuất hiện trong vật liệu biến tính. Thí nghiệm mẻ đánh giá sự ảnh hưởng của pH, thời gian và nồng độ của vật liệu tự nhiên và biến tính đến khả năng hấp phụ ion Cu(II). Kết quả của thí nghiệm mẻ phù hợp với mô hình Langmuir với khả năng hấp phụ cực đại đạt 28,17 mg/g tại nồng độ pH tối ưu là 5,5. Kết quả thí nghiệm trên mô hình cột cho thấy đường cong thoát của quá trình hấp phụ của vật liệu biến tính và chưa biến tính phụ thuộc và chiều cao lớp vật liệu, nồng độ ion Cu(II) ban đầu và vận tốc dòng chảy qua cột. Các dữ liệu thu nhận được từ thực nghiệm phù hợp với mô hình động học Yoon-Nelson.