Removal of turbidity, methylene blue and heavy metals from contaminated water using pyro-processed coconut shell and fiber
Kasimu, Titus Munyao
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Water is essential for all domestic and development activities worldwide. It‟s continues contamination by heavy metals is a major concern to many developing countries, Kenya included as they are non-biodegradable and toxic. This is expected to increase in tandem with the projected population and industrial growth. Therefore, it is important to systematically minimize the percentage concentration of the heavy metal ions in waste water before use or discharge into water bodies. Methods in operation for removal of the heavy metal ions in wastewater include: chemical coagulation, ion-exchange, electrochemical, adsorption, membrane process and ultra-filtration. Most of these methods are uneconomical due to high costs, extremely highly toxic sludge and inefficient removal of heavy metals. This motivated the current research work to explore simpler methods of wastewater treatment that can be economically viable and environment friendly in arid and semi-arid regions in developing countries. Coconut shell and its fiber are locally available agricultural waste which can be converted by activation into adsorbents for water remediation due to its fineness and large surface area. The present study was set to investigate the potential of activated coconut shell, fiber and their charcoals to remediate water contaminated with Pb2+ and Cd2+ ions, methylene blue and turbidity. Coconut shell and fiber adsorbents were activated with sodium hydroxide while charcoal was obtained by burning shell and fiber which had been soaked in phosphoric acid in limited air. The ability of adsorbents to adsorb lead (II) and cadmium (II) ions from wastewater was investigated by carrying out batch experiment and varying parameters such as initial concentration, adsorbent dose, contact time, agitation speed, temperature and pH were varied. Fourier Transform Infrared Spectrum analysis detected presence of functional groups of COO¯, O-H, C=O, C-O-C and RNO2 in adsorbents upon activation which are responsible for adsorption. Results demonstrated that, data for Cd2+ and Pb2+ ions best fitted into Freundlich model with maximum adsorption capacities of 6.14 mg cadmium/g activated coconut fiber and 7.71 mg lead/g coconut fiber charcoal respectively. Methylene blue best fitted in Langmuir isotherm model with higher adsorption capacity of 7.16 mg/g in activated coconut fiber charcoal. The efficiency of all adsorbents in removal of methylene blue was below 15 platinum cobolt recommended by WHO with activated coconut fiber charcoal found displaying 99.9% removal. The efficiency of activated coconut fiber charcoal, activated coconut shell charcoal, activated coconut fiber, activated coconut shell and coconut fiber charcoal towards removal of turbidity increased with increase in dosage with a notable removal of 99.65%, 99.59%, 97.31%, 99.45%, and 99.41% when 1.0g, 1.0g, 1.0g 2.0g and 1.0g of adsorbent were used respectively. The results from this study suggest that activated coconut shell, fiber and there charcoals are potential adsorbents of Cd2+ ions, Pb2+ ions, methylene blue and turbidity.