oa South African Journal of Chemical Engineering - The removal of Co2+, V3+ and Cr3+ from waste effluents using cassava waste



The existence of heavy metals from industrial effluents can have serious effects in the aqueous system. Most of these metals cannot be effectively removed from the effluents using conventional methods because of various factors. Therefore, alternative methods are required. This paper presents a study for the removal of cobalt (Co2+), vanadium (V3+) and chromium (Cr3+) ions from synthetic wastewater using untreated and acid treated cassava waste biomass. Cassava waste biomass is a cellulosic material which possesses hydroxyl groups when untreated and sulfhydryl groups (or thiol groups) when treated with thioglycollic acid. Both these functional groups can act as binding sites for metal ions. The effects of various parameters (e.g., pH, temperature, agitation, metal ion concentration, etc.) on the removal of metal ions from the solutions were investigated in a batch process. Adsorption of metal ions was observed to increase with pH. The maximum metal ion adsorption was obtained at pH of 3 for V3+, 6 for Co2+ and 3 for Cr3+. Metal adsorption increased with an increase in temperature from 30 to 40°C at an initial metal concentration of 100mg/L. However, there was a reduction in adsorption beyond 40°C for all the metal ions. It was found that treated biomass had higher adsorption rates. Furthermore, the results showed that an increase in the concentration of thioglycollic acid improved the adsorptivity of the cassava waste biomass. The work also showed that the cassava biomass could be regenerated and reused up to six adsorption-desorption cycles. Amongst the two widely used isotherms tested (i.e., Langmuir and Freundlich models), the experimental data was found to fit the Freundlich isotherm better.


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