Several potential sorbent materials containing iron oxides were prepared and evaluated for potential to remove divalent metals from waste waters. These included a ferrihydrite-coated sand, maghemite incorporated in Dowex[Trademark] ion exchange resin, gothite and two thermally activated ferrihydrites. Attempts to prepare sorbents from steel shot by coating with ferrihydrite or by thermal oxidization resulted in cemented solids rather than pellets. Ferrihydrite activated at 295��C had a surface area of 113-202 m��/g, followed by gothite at 72-92 m��/g and ferrihydrite-coated sand at 0.78-1.4 m��/g. Zinc adsorption was evaluated by placing 5 g ferrihydrite-coated sand, 0.1 g maghemite in Dowex or 0.1 g gothite in batch reactors containing 40-50 mL of zinc solution, adjusting to various pH values, allowing to react for 96 hours, and analyzing the supernatant for zinc. The data fitted poorly to an ion exchange model using nonlinear regression. The adsorption site densities determined from the regression analysis were 8.0x10������ moles per gram of ferrihydrite-coated sand and 4.1x10������ moles per gram of White. Maghemite in Dowex did not provide any additonal zinc removal capacity in excess of the ion exchange capacity of the resin. Kinetic experiments showed that zinc adsorption onto ferrihydrite-coated sand was 86% complete after 96 hours. Based upon this study, the most promising sorbent appears to be gothite, although the "activated ferrihydrites" are also worthy of further study. Neither ferrihydrite-coated sand and maghemite in Dowex appear to be practical sorbents, based on their low zinc adsorption site density. Maghemite in Dowex might be useful in applications requiring magnetic sorbents. / Graduation date: 1999

Typescript (photocopy). / Digitized by Kansas Correctional Industries

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 2016 / The remediation of acid mine drainage (AMD) has received much attention over the years due to the environmental challenges associated with its toxic constituents. Although, the current methods are able to remediate AMD, they also result in the loss of valuable products which could be recovered and the financial benefits used to offset the treatment costs. Therefore, this research focused on the removal of toxic heavy metals as well as the recovery of acid using a low cost adsorbent and acid retardation process, respectively. In the first aspect of the study, three low cost adsorbents namely zeolite, bentonite clay and cassava peel biomass were evaluated for metal uptake. The adsorption efficiencies of zeolite and bentonite, was found to be less than 50% for most metal ions, which was lower compared to the 90% efficiency obtained with cassava peel biomass. Subsequently, cassava peel biomass was chosen for further tests. The metal removal efficiency using the cassava biomass was in the order Co2+> Ni2+> Ca2+> Mn2+> Fe3+> Mg2+. The highest metal removal was attained at 2% adsorbent loading and 30 ˚C solution temperature. Amongst the equilibrium models tested, the experimental data was found to fit well with the Langmuir isotherm model. Column studies using the immobilized cassava waste biomass suggested that the breakthrough curves of most metal ions did not resemble the ideal breakthrough curve, due to the competitive nature of the ions present in the AMD used in this study. However, the experimental data from the column tests was found to correlate well with the Adam-Bohart model. Sulphuric acid recovery from the metal barren solution was evaluated using Dowex MSA-1 ion exchange resins. The results showed that sulphuric acid can be recovered by the resins via the acid retardation process, and could subsequently be upgraded to near market values of up to 70% sulphuric acid using an evaporator. Water of re-usable quality could also be obtained in the acid upgrade process. An economic evaluation of the proposed process also showed that it is possible to obtain revenue from sulphuric acid which could be used to offset some of the operational costs. / M T 2016

M. Tech. Engineering : Chemical. / Evaluates the applicability of adsorption, biodegradation and hybrid adsorption and biodegradation system in treatment of wastewater containing melanoidin.Treatment of wastewater containing melanoidin through SAB process in fluidized bed bioreactor results in the best performance index as compared to adsorption and biodegradation processes undertaken singly. The synergies realized are more pronounced in fluidized bed bioreactor than in stirred tank system.

Nitroguanidine (NQ) is a nitramine used in many propellant formulations. The purpose of this study was to develop a method for treating nitroguanidine process wastewaters. The major wastewater contaminants were found to be nitroguanidine and guanidine nitrate (GN) (an intermediate product). Pilot tests were conducted for the removal of nitroguanidine using granulated carbon adsorption (GAC) and ion exchange for the removal of GN. The nitroguanidine concentration in demonstration plant wastewater was reduced from 15.5 mg/L to less than 1 mg/L. The carbon capacity was found to be 0.045 g NQ/g carbon. Strong acid resin was found to reduce guanidinium ion Gu⁺ concentration from 14.5 mg/L to 1 mg/L with a resin capacity of 0.13 eq Gu⁺ /L resin. No significant reduction in resin capacity for Gu⁺ was experienced after five regenerant cycles. A unique two-step regeneration was used. This included a 5% calcium nitrate solution to produce a spent regenerant that could be recycled to the production process. This was followed by regeneration with a 15% sodium chloride solution to place the resin in the sodium form. Anion exchange was used for the removal of nitrate ions. / Master of Science

Submitted in fulfilment of the requirements of the degree of Master of Engineering - Chemical, Durban University of Technology, Durban, South Africa, 2015. / Industrial wastewater containing organic compounds and/or substances is an increasing problem due to its increasing toxic threat to humans and the environment. The removal of organic compounds has become an imperative issue due to stringent measures that are introduced by the Department of Environmental Affairs in South Africa to enforce regulations concerning wastes that emanate from petrochemical industries. Thus, wastewater containing these compounds must be well understood so as to device adequate treatment processes. In this study, the adsorptive capacity of PAD 910 polystyrenic resin originating from China and granular activated carbon (GAC) was evaluated for the removal of benzene, toluene, ethylbenzene and isomers of xylene (BTEX) from an aqueous solution. Batch studies were performed to evaluate the effects of various experimental parameters such as mixing strength, contact time, internal diffusion, adsorbates and initial concentration on the removal of the BTEX compounds. The experiments were conducted at the mixing strength of 180 rpm, in order to comfortably assume negligible external diffusion. The equilibrium isotherms for the adsorption of the adsorbates on the PAD 910 polystyrenic resin were analyzed by the Langmuir, Freundlich and linearized Dubinin-Radushkevich models at a pH of 5.86. The Langmuir model fitted the data adequately; this result was supported by the work done by Site (2001) which concluded that the Langmuir is the most practical model in representing the adsorption of aromatic compounds. The Langmuir model indicated that resin has the highest adsorption capacity of 79.44 mg/g and GAC has 66.2 mg/g. Resin was found to adsorb 98% of benzene, 88% of toluene, 59% of ethylbenzene, 84% m-;p-xylene and 90% o-xylene at an initial concentration of 14.47 mg/l. BTEX adsorption was a two-stage process: a short, fast initial period then followed by a longer, slow period corresponding to the intra-particle diffusion of BTEX molecules in macropores and micropores. The adsorption capacity was determined by total surface area accessible to BTEX and the availability of active surface chemical groups. The dependence of adsorption capacity on the surface of the two adsorbents and temperature was observed, suggesting the chemical nature of the BTEX adsorption. The interaction between BTEX/activated carbon was however weak and energetically similar to that of hydrogen bonds. Generally, BTEX adsorption was an exothermic process that combined physisorption and chemisorption. The PAD 910 polystyrenic resin had a greater specific surface area (SSA) of 1040 m2/g which yielded in higher capacity compared to GAC which had a low SSA of 930 m2/g. The normalized adsorption capacity was found to be higher for PAD 910 polystyrenic resin than GAC (0.66 and 0.27 mg/m2 respectively) which suggests that the resin has a good potential of the adsorbent for removing BTEX compound compared to GAC. Fixed bed columns were used to evaluate the dynamic adsorption behaviour of BTEX/PAD 910 polystyrenic resin through a dynamic column approach. The performance of small-scale fixed bed columns, each containing PAD 910 polystyrenic resin and the other containing GAC were evaluated using 14.47 mg/L of BTEX concentration. The columns with 32 mm diameter, studied bed depths of 40, 80 and 120 mm and flow rate of 6 ml/min were used in order to obtain experimental breakthrough curves. The bed depth service time (BDST) model was used to analyze the experimental data and design parameters like adsorption capacity, adsorption rate and service time at 20% and 60% breakthrough. BDST was also used to predict the service times of columns operated under different influent concentrations and flow rates to produce theoretical values that were compared to the experimental values. Adsorption model by Dubinin and colleagues (Dubinin, 1960), based on the theory of volume filling micropores was used to fit the measured adsorption isotherms. Agreement between the modelled and experimental results for GAC and PAD 910 polystyrenic resin using Dubinin-Radushkevich equation generally improved with increasing the surface area and produced reasonable fits of the adsorption isotherms for both GAC and PAD 910 polystyrenic resin. Granular activated carbon had a lesser performance compared to the PAD 910 polystyrenic resin, in terms of kinetic studies, and this finding was attributed to the pore structure which made accessibility of BTEX molecules more difficult in this study. The results indicate that PAD 910 polystyrenic resin show potential as an adsorbent for removing low concentrations of BTEX from wastewater. It is suggested that necessary treatment of GAC might improve the performance of this adsorbent by creating more mesopore volume and fraction which is essential to enhance adsorption rate. A substantial different SSA could be achieved through high porosity development in GAC by using templating method with a higher potassium hydroxide mixture ratio.