Biosorption of Hexavalent Chromium Ions from Aqueous Solutions using Almond Green Hull as a Low-Cost Biosorbent

Raw agricultural wastes are affordable adsorbents for the removal of heavy metals from aqueous solutions. In this research, the use of almond green hull (as an eco-friendly and low-cost adsorbent) with no treatment having the ability to remove toxic hexavalent chromium (Cr (VI)) from aqueous solutions has been investigated. The influences of several main parameters such as pH value of solution, sorbent amount, initial metal-ion concentration, and contact time in batch experiments have been studied. The results revealed that almond green hull adsorbs over 94.14% of Cr (VI) from solutions containing 10 mg/L of Cr(VI) at sorbent amount of 4 g/L and pH=6 after 30 min of equilibration at room temperature. High removal efficiency of Cr (VI) occurred in the first 5 min of sorbent contact time for concentration of 10 mg/L solution. Adsorption isotherms were compared with both Langmuir and Freundlich adsorption models. The experimental data best fit with the Langmuir isotherm model with R 2 =0.9989. The present study revealed that such a lowcost material could be used as an efficient sorbent for the removal of Cr(VI) from aqueous solutions.