Adsorption of Cu2+, Pb2+, and Cd2+ onto oiltea shell from water.

Agro-processing waste oiltea shell (OTS) has been previously proven effective in removing dye from water by adsorption. This study further evaluated its capability to adsorb heavy metals in aqueous solution. Adsorbent dosage, pH, ion concentration, temperature, and contact time were investigated in batch experiments. Pseudo-second order kinetic better described the adsorption process for the three ions. Langmuir equation was more suitable for Cu2+ and Cd2+, while Freundlich for Pb2+. The maximum adsorption capacity was 22.4 (Pb2+), 12.1 (Cu2+), and 14.2 mg/g (Cd2+), respectively. The adsorption was spontaneous and endothermic. Adsorption was then performed in column and Thomas model was fitted, based on which the maximum adsorption capacity was 7.42 (Cu2+), 4.17 (Pb2+), and 18.02 mg/g (Cd2+), respectively. High removal rate of metal ions and dye methylene blue was also achieved from their mixture solution. OTS is therefore a promising biosorbent in treating wastewater with organic and inorganic pollutants.