Biosorption of Cr(VI) on Japanese cedar bark

The ability of Japanese cedar (Cryptomeria japonica) bark to remove Cr(VI) from aqueous solutions was investigated. The research parameters included the solution pH, temperature, and initial concentration of Cr(VI) in solution. The removal of Cr(VI) was highly solution pH dependent and adsorbate concentration dependent, and mainly governed by physicochemical adsorption under the weak acidic conditions studied (initial solution pHgreater than or equal to3). However, the reduction of Cr(VI) to Cr(III) occurred extensively at low solution pH (initial solution pHless than or equal to2). The equilibrium data at different temperatures fit well in the Langmuir isotherm model. The endothermic nature of the adsorption was confirmed by the positive value of enthalpy change (18.9 kJ mol(-1)). The positive value of entropy change (65.2 J mol(-1) K-1) suggested the increased randomness at the solid-solution interface during the adsorption. The studies showed that Japanese cedar bark can be used as a cost-effective adsorbent for the removal of Cr(VI) from wastewater.