Studies on the Influence of Mercaptoacetic Acid (MAA) Modification of Cassava (Manihot sculenta Cranz) Waste Biomass on the Adsorption of Cu²⁺ and Cd²⁺ from Aqueous Solution

Cassava peelings waste, which is both a waste and pollutant, was chemically modified using mercaptoacetic acid (MAA) and used to adsorb Cu²⁺ and Cd²⁺ from aqueous solution over a wide range of reaction conditions at 30 .deg. C. Acid modification produced a larger surface area, which significantly enhanced the metal ion binding capacity of the biomass. An adsorption model based on the Cu²⁺/Cd²⁺ adsorption differences was developed to predict the competition of the two metal ions towards binding sites for a mixed metal ion system. The phytosorption process was examined in terms of Langmuir, Freundlich and Dubinin-Radushkevich models. The models indicate that the cassava waste biomass had a greater phytosorption capacity, higher affinity and greater sorption intensity for Cu²⁺ than Cd²⁺. According to the evaluation using Langmuir equation, the monolayer binding capacity obtained was 127.3 mg/g Cu²⁺ and 119.6 mg/g Cd²⁺. The kinetic studies showed that the phytosorption rates could be described better by a pseudo-second order process and the rate coefficients was determined to be 2.04 x 10^-3 min^-1 and 1.98 x 10^-3 min^-1 for Cu²⁺ and Cd²⁺ respectively. The results from these studies indicated that acid treated cassava waste biomass could be an efficient sorbent for the removal of toxic and valuable metals from industrial effluents