Removal of Hexavalent Chromium from Aqueous Solution by Leaf Litter Biomass

Abstract

Feasibility of eight different waste leaf litter biosorbents of plant origin were investigated for removal of hexavalent chromium from synthetic aqueous solution in batch and continuous mode of sorption. The objective was to develop inexpensive and effective metal ion adsorbents that are available in large quantity as an alternative to existing commercial adsorbents. The different leaf litter biomass, Eucalyptus, Ashoka, Bamboo, Mango, Poplar, Wheat Husk, Rice straw and Jamun were used to carry Cr (VI) sorption process under shake flask conditions at pH 5 and a temperature of 28°C and agitation rate of 120 rpm in batch mode. The effect of varied biomass concentration, pH, initial metal concentration and contact time to remove Cr (VI) from aqueous solution was studied. Maximum removal of Cr (VI) from aqueous solution by the Eucalyptus, Bamboo, Poplar, Jamun leaf litter biomass, wheat husk and Rice straw was observed in 1 hour, thereafter it reached equilibrium. Removal of Cr (VI) from aqueous solution was 94% by Eucalyptus, 94% by Bamboo, 84% by Poplar leaf litter biomass, 83% by Wheat Husk biomass, 82% by Mango leaf litter biomass, 82% by Jamun leaf litter biomass, 77% Ashoka leaf litter biomass, and 22% by Rice Straw biomass in 1 hour of contact using 4% of adsorbent. Combination of four biomasses i.e. Eucalyptus, Mango, Bamboo and Wheat husk was effective in removal of Cr (VI) from metallic solution at varying initial concentration i.e. 10 mg/l to 100 mg/l of Cr (VI) in aqueous solution. The removal efficiency at 20, 30, 40, 50 and 60 mg/l of initial metal concentration was 97, 97, 96, 96, and 94% respectively in 30 min of contact. In continuous flow sorption column packed with dry biomass of combination of four different leaf litter biomass namely, Eucalyptus, Bamboo, Mango and Poplar in the ratio of 1:1:1:1, 95% and 94% of metal removal at 10 mg/l and 20 mg/l of initial metal concentration was observed. Adsorption isotherms Equilibrium sorption data of Cr (VI) was used to predict conventional Langmuir and Freundlich isotherm, which suggested involvement of either physico-chemical or ion exchange interaction in chromium binding. Fourier transform infrared spectral analysis revealed that different types of functional groups, aliphatic amines, primary amines and alkanes played an important role in metal binding.