Biosorption of Cr3+ and Pb2+ from tannery wastewater using combined fruit waste

Abstract

In recent years, tanning industries have been proved to be among the major contributors of heavy metals. Different convectional and biological method has been used to remove these heavy metals from tannery wastewater but most of these technologies are costly and not easily accessible. This research is aimed at determining the efficiency of combining the waste rind of Citrulus lanatus and waste peel of Citrus sinensis as a low cost biosorbent for the removal of Cr3+ and Pb2+ pollutants present in tannery wastewater. The selected biosorbents where surface characterized and point of zero (pHPZC) was determine with pH adjusted using NaOH solution to be between 2-12. The adsorption process of Cr3+ and Pb2+ by the selected biosorbent was determined under factors such as contact time, pollutants dosage, absorbent dosage, and particle size. The Lagmuir equation and Freundlich isothermal were used to determined adsorption equilibrium while pseudo first order and pseudo second order were used to determine the adsorption kinetics. The result obtained shows that Citrulus lanatus has better adsorption of Pb3+ (86%) while the combined fruit better adsorption of Cr3+ (85%) under the all factors. The Lagmuir equation and Freundlich shows suitability of indicating equilibrium sorption for Cr3+ and Pb2+. The adsorption kinetic study shows that pseudo-second order obeys kinetics model signifying that absorption occurs by chemisorptions. The combination of the waste rind of Citrulus lanatus and waste peel of Citrus sinensis is an effective low cost biosorbent for the removal of Cr+3 and Pb+2 pollutants present in tannery wastewater.