Biochars evaluation for chromium pollution abatement in chromite mine wastewater and overburden of Sukinda, Odisha, India

Abstract

The present work explored the prospect of corncob biochar (CCBC), Ipomoea biochar (IBC), and modified corncob biochar composites (MCBC) for abatement of Cr-polluted mine wastewater and overburden collected from Sukinda chromite mine, India. Biochars are produced through the thermo-chemical process at 300, 500, and 700 degrees C, and MCBC using 1 M FeSO4.7H(2)O at 800 degrees C. Synthetic Cr solutions (10-800 mg/L) batch adsorption experiments with varying pH (2 - 10), time (5 min - 48 h), and biochar doses (0.1-7 g/100 mL) ascertained Langmuir and Freundlich isotherm along with maximum Cr adsorption capacity. Subsequently, adsorptions of Cr from chromite mines wastewater by biochars were assessed. Also, the influence of biochars' dose (1 and 5 % w/w) on water and plant available Cr in overburden was determined for 90 days timespan. Maximum Cr (VI) adsorption was relatively higher from synthetic Cr solution by MCBC (142.8 mg/g). Among biochars, MCBC also adsorbed comparatively higher Cr-total (> 90%) and Cr (VI) (> 75%) from all the three wastewater. MCBC reduced relatively higher water leachable (from 4.88 to 0.87 mg/L) and enhanced phytoavailable Cr fraction (5.73 to 7.41 mg/L) in overburden with a 5 % dose within 90 days. The MCBC larger surface area (308.37 m(2) g(-1)), acidic pH (<= 3), and presence of iron/sulfur (Fe/S) resulted in better Cr pollution reduction (higher adsorption and lower water leachability) and remediation (higher plant available fraction) potential. The research findings recommend utilization of MCBC for Cr pollution remediation in both chromite mine wastewater and overburden dump.