Biosorption of chromium(VI) from industrial wastewater onto pistachio hull waste biomass

Raw agricultural waste is an affordable adsorbent for the removal of industrial contaminants. In the present work, pistachio hull powder (PHP) was investigated for the removal of hexavalent chromium (Cr(VI)) from wastewater. The effects of pH (2–8), PHP concentration (0.5–8 g/L), Cr(VI) concentration (50–200 mg/L), temperature (5–50 °C) and contact time (1–60 min) were studied on the removal of Cr(VI) from aqueous solution. The results revealed that PHP adsorbs over 99% of chromium from solutions containing 50–200 mg/L of Cr(VI) at a pH of 2 and an adsorbent concentration of 5 g/L after 60 min of equilibration. The percent chromium adsorbed from solution increased with an increase in temperature from 5 to 40 °C. Kinetic and isotherm modeling studies demonstrated that the experimental data best fit a pseudo-second order and Langmuir model, respectively. The maximum Langmuir adsorption capacity was 116.3 mg/g. In the second part of the study, the efficacy of PHP was examined by analyzing the removal of Cr(VI) from industrial wastewater. Results revealed that 2 g/L of PHP decreased the Cr(VI) concentration from 25 mg/L to less than 0.05 mg/L after 30 min of equilibration. In summary, biosorption onto PHP is an affordable and simple process for treating Cr(VI)-laden industrial wastewaters.