Evaluation of Cadmium Removal in an Aqueous Solution by Biosorption in a Batch System with Banana, Peanut, and Orange Husks

At present, the amount of heavy metals in some aquifers exceeds the limits established by standards, especially in developing countries. Cadmium is present in high concentrations in aquifers; contact with cadmium can lead to some adverse health effects. Adsorption is one of the most efficient and low-cost methods currently used to separate heavy metals from water systems. In order to obtain a sustainable heavy metal adsorption system, abundant, low-cost, biodegradable, and easy-to-treat organic waste compounds were sought. Three biosorbents were chosen: orange, peanut, and banana peel, which, due to their functional groups, can attract the positive ions of metals and form a bond that allows them to be absorbed and separated from the aqueous solution. The presence of functional groups such as -OH, -CO, -COO−, and -N-H were found to be the main responsible for biosorption (FTIR). Square wave voltammetry was used to analyze the amount of cadmium in an aqueous solution. It was found that the systems with the best adsorption capacities were untreated peanut peel (284.2 mg/g), untreated orange peel (275.5 mg/g), and treated banana peel (229.21 mg/g). Treatment of the peels for cadmium uptake is not recommended.