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Title: Biosorption of selected heavy metal ions and methylene blue from aqueous solution using chemically treated Luffa cylindrica
Author: Amba, Akanimo Emene
ISNI:       0000 0004 7425 7458
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2018
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The production of industrial wastewater is a threat to the environment when it contains heavy metals and organic pollutants that are above the World Health Organisation (WHO) requirement levels expected in all waters. A lot of this pollution comes from industrial activities. Conventional methods, such as chemical precipitation and reverse osmosis, had been utilized to treat these wastewaters but due to the challenges of creating more waste in the form of sludge, high cost and the need to remove pollutants to lower levels, new methods are needed to treat industrial wastewaters. Wastewater treatment by biosorption, a low cost and efficient process, is an economically viable option for industries. The utilisation of this treatment process has not been fully implemented due to the complex and not fully understood nature of the biosorption systems. To optimise the process is to choose a suitable adsorbent and to study the parameters that influence the adsorption design system. Some of the most detrimental heavy metal ions found in industrial wastewater are lead, zinc and cadmium. These heavy metal ions cause many health problems and are of great environmental concern. A chemically modified (alkali or acid treated) adsorbent, Luffa cylindrica (L. cylindrica), with a high affinity for heavy metals, was used to adsorb heavy metal ions from aqueous environmental solution under various experimental conditions. The potential use of L. cylindrica to successfully remove an organic pollutant, methylene blue (MB), a cationic dye, from aqueous solution was investigated. The L. cylindrica, when chemically treated with 4% NaOH and 4% HCl shows an increased amount of ion exchange functionality and structural change, thereby enhancing the adsorption capacity. Experimental factors of adsorption time, initial metal ion concentration, ionic strength and pH of solution were studied for the different pollutants both alone and in mixed solutions. The experimental data were analysed with kinetic and isotherm models. From the FT-IR spectra, protonated hydroxyl and carboxyl functional groups was observed. The adsorption of lead, zinc, cadmium ions and MB onto chemically treated L. cylindrica material was investigated in both batch and column experiments. Adsorption isotherm models, Langmuir, Freundlich, two-site Langmuir, Temkin, DubininRadushkevich and Sips; Thomas and Yoon-Nelson models were utilized in understanding the adsorption mechanism and the ability of the adsorption system evaluated. The maximum adsorption capacity is 24.9mg/g, 8.8mg/g & 37.0mg/g for lead, cadmium and zinc respectively as described by the Langmuir isotherm and the maximum percentage uptake (efficiency) is 96.4%, 60.7% & 77.6% respectively. The equilibrium data for MB was well represented by the Freundlich isotherm model, and supported by the Temkin model, which showed a highly heterogeneous nature of the adsorption. A significant difference of adsorption capacity occurred under dark and light conditions. The maximum adsorption uptake reached within 60 minutes was at 99% adsorption efficiency for methylene blue concentrations of 5-40 mg/L. Using the Excel SOLVER, the best fit model was found for each metal ions adsorption onto the L. cylindrica. The kinetics of the biosorption process was studied. A pseudo second order model shows a good correlation fit for all heavy metals ions and MB adsorption. In agreement with the literature, the optimum condition for the maximum adsorption capacity for lead, cadmium, zinc and MB occurs at pH 5, 7, 6 & 7 respectively at room temperature. These studies show that heavy metal ions and methylene blue were found to bind differently to the two active binding sites of the heterogeneous surface of the L. cylindrica. The multiple adsorption system differs from the single adsorption system and an alteration of these systems would optimise the adsorption process. The cost evaluation attempted to show a feasible adsorption process for developing countries. An understanding of the use of Luffa cylindrica for the removal of pollutants from industrial wastewater will improve the commercial application of adsorption processes in their treatment.
Supervisor: Edyvean, Robert ; Ogden, Mark Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available