Kinetic and Isotherm Modelling of adsorption of Cr 3+ metal ions from Tannery wastewater on to unmodified and acid-modified Arabica coffee husks biosorbents

Abstract

The kinetics and isotherm modeling of adsorption of Cr3+ ions onto unmodified coffee husk (UCH) and acid modified coffee husk (MCH) biosorbent were successfully studied in batch experiments. Equilibrium data were analyzed by Langmuir and Freundlich isotherm models. Equilibrium data best fitted to Langmuir isotherm. The Langmuir adsorption capacity was higher in MCH (6.64 mg/g) compared to the UCH (3.85 mg/g). The adsorption constant, b, was less than one in the two adsorption processes suggesting a high affinity of both the UCH and MCH adsorbent for Cr3+ ions. The experimental data were fitted well with pseudo second order kinetics with best fitness for both the UCH and MCH with regression coefficient (R2 ) of 0.9792 and 0.9956, respectively. The findings revealed that the unmodified and modified coffee husks have potential in removal of Cr3+ from tannery wastewater