Biosorption and health risk assessment of arsenic contaminated water through cotton stalk biochar

Arsenic (As) contamination in water has become a worldwide concern for public and environmental health owning to its non-degradable and toxic nature. Recently, elevated concentrations of As have been documented in groundwater, which needs remediation through low-cost technology. Cotton stalks derived biochar (CSB) is a new adsorbent material that may have the potential to remove As(III) from an aqueous solution. Therefore, in this study, the potential of CSB for sorption and removal of As(III) was evaluated at optimized operational conditions viz. contact time, concentrations of CSB, and As(III). Moreover, the health risk assessment of treated water was also determined to monitor the effectiveness of CSB-treatment for various As-concentrations. The CSB was characterized for Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and point of zero charges (PZC) to explore surface moieties that facilitate As(III) sorption on the CSB. Results revealed that maximum sorption capacity (q) of As(III) was 89.90 mu g g(-1) (at 1 g CSB L-1, pH 6, contact time 2 h, As concentration 200 mu g L-1). The removal of As(III) decreased with increasing As concentration in the aqueous solution. The Langmuir model was suitable to explain the sorption of As(III) on CSB with maximum sorption (q(max) = 102.78 mu g g(-1), R-2 = 0.99). High As(III) sorption might be attributed to high surface area (103.62 m(2) g(-1)) and presence of different functional groups (-OH, C=O, C-O) on the CSB surface that facilitated As(III) sorption and removal. The hazard quotient (HQ) of As-treated water showed HQ-values >1 (3.79 +/- 0.056, 2.00 +/- 0.030 and 1.31 +/- 0.102 at adsorbent biomass of 1, 2 and 3 g CSB L-1, respectively at a concentration of 50 mu g As L-1), indicating a harmful effect of As-treated water on human health. This study shows that CSB is an efficient adsorbent material and may be employed to remove a low concentration of As(III) from water, however, it should be monitored carefully for its risk to human health.