Batch and Continuous Removal of Copper and Lead from Aqueous Solution using Cheaply Available Agricultural Waste Materials

The potential of six economically cheap agricultural waste materials, viz. rice husk, betel nut peels, sugarcane molasses, tea waste, mustard oil cake and saw dust, was investigated for copper and lead removal from aqueous solutions under batch and continuous conditions. The effect of pH, contact time, sorbent dose and initial metal ion concentration on the uptake of copper and lead was first examined in batch mode. Rice husk was found to be the best among the tested biosorbents with a maximum removal of 72.17 % and 85.87 % for copper and lead, respectively. The batch sorption data correlated well with SIPS, Redlich- Peterson, Freundlich and Langmuir isotherms models. Heavy metal sorption kinetics was best explained by the diffusion based second order kinetics model. Fourier transform infrared analysis of rice husk, before and after heavy metal sorption, revealed the involvement of mainly hydroxyl, amine, and carboxyl functional groups in lead and copper removal by rice husk. Dynamic removal of lead and copper by rice husk was examined as a function of different bed height and flow rate using fixed-bed columns, which yielded a maximum saturation time of 14 hours. The metal breakthrough curves obtained were analysed using the Thomas, BDST, Yoon-Nelson and Clark breakthrough models. The simulation of breakthrough curve for the metals was successful with BDST, Yoon-Nelson and Clark models. Removal of bound lead/copper from the loaded column was finally achieved by using 0.1M HCl as the eluant, which yielded complete desorption of the metals in nearly 60 min.