Abstract

ADSORPTIVE REMOVAL OF CR (VI) ION FROM WASTEWATER BY ACTIVATED COFFEE HUSK AND BANANA PEEL: COMPARATIVE STUDY

Asnake Gudisa Ede*

Abstract

This study reports the biosorption of Cr (VI) on surface of acid activated coffee husk (CH) and banana peel (BP). The common functional groups identified at the surface of the CH and BP were OH - -COOH, and –NH. A contact time of 240 and 60 minutes assured attainment of equilibrium for CH and BP, respectively. The maximum adsorption capacity of CH was 59.54 ± 0.63 and for BP was 18.60 ± 0.01 mgg -1. As the dose increased, removal efficiency increased with statistical significance for both cases (p<0.05) despite CH removal efficiency is better than BP for same dose used. The optimum pH for CH was 2.1 ±0.01 and for BP was 4.50 ± 0.01. The optimum temperature for removal of Cr (VI) with both adsorbents was 30ºC. The sorption model followed Langmuir for the two adsorbents (R2=0.955 for CH; R2=0.975for BP).The experimental data fitted pseudo second order kinetic model (R2=0.994 and R2=0.975 for BP).The reaction was spontaneous in nature as ΔGo =-4.63 for CH; =-2.47kJ/mol for BP. This showed CH and BP are suitable candidates for use as biosorbents in the removal of heavy metals from aqueous solutions.

Keywords: Banana peel, Biosorption, Isotherms, Kinetics.