Mango peel waste (MPW) was evaluated as a sorbent for the removal of Cd2+ and Pb2+ from aqueous solution [176]. The maximum sorption capacity of Cd2+ and Pb2+ was found to be 68.92 and 99.05 mg/g, respectively. The kinetics of sorption of both metals was fast, reaching equilibrium in 60 min. Sorption kinetics and equilibria followed pseudo-second-order and Langmuir adsorption isotherm models. FTIR analysis revealed that carboxyl and hydroxyl functional groups were mainly responsible for the sorption of Cd2+ and Pb2+. Chemical modification of MPW for blocking of carboxyl and hydroxyl groups showed that 72.46% and 76.26% removal of Cd2+ and Pb2+, respectively, was achieved due to the involvement of carboxylic group, whereas 26.64% and 23.74% was due to the hydroxyl group. EDX analysis of MPW before and after metal sorption and release of cations (Ca2+, Mg2+, Na+, K+) and proton from MPW with the corresponding uptake of Cd2+ and Pb2+ revealed that the main mechanism of sorption was ion exchange. The regeneration experiments showed that the MPW could be reused for five cycles without significant loss in its initial sorption capacity. The same researchers also studied the potential of mango peel for the removal of Cu2+, Ni2+, and Zn2+ from constituted metal solutions and genuine electroplating industry wastewater [177].