Removal of nickel (II) ion by adsorption on coconut copra meal biosorbent

摘要

The present study explores the utilization of biomass from coconut copra meal (CCM) as a biosorbent to remove nickel (II) ions (Ni(II)) from aqueous solutions. CCM biomass can be processed into a sorbent easily due to its soft nature derived from the molecular composition of -mannan which is different from -glucose found in other cellulosic biomass. The sub-micrometer structures on the prepared CCM sorbent were revealed by SEM. The prepared CCM sorbent was porous with many openings. Investigations on the effects of solution pH, biosorbent dose, initial metal concentration, contact time, and temperature were carried out to determine the optimum biosorption conditions in a batch system. The kinetics, adsorption isotherms, and adsorption thermodynamics of Ni(II) biosorption onto the CCM biosorbent were investigated. The experimental data were analyzed for the biosorption kinetics by using the pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. It was observed that the pseudo-second-order model fitted better with the kinetics data of Ni(II) biosorption as compared to other models. Adsorption isotherm studies revealed that the Langmuir isotherm model showed a better fit for the experimental data when compared to the Freundlich isotherm model. The maximum monolayer capacity of CCM for Ni(II) was determined to be 3.77mg/g. From the thermodynamic studies, the positive value of H degrees indicates that the adsorption is an endothermic process and mainly attributed by a physical sorption. The negative values of G degrees indicate that the process is spontaneous. The desorption process was evaluated and it was found that 0.1M HNO3 was able to desorb almost 100% of Ni(II) that adsorbed on the CCM biomass. The study of co-ions effect showed small decreases in biosorption of Ni(II) in the presence of Co(II), and more decreases with the Pb(II) presence. This study reveals the feasibility of an economical process to remove Ni(II) from wastewater by the CCM biosorbent.