Strategies for crystal violet dye sorption on biochar derived from mango leaves and evaluation of residual dye toxicity

The present study aimed to determine the sorption behaviour of crystal violet (CV) dye on mango leaves biochar (MLBC) prepared at 400 °C, 600 °C and 800 °C. Response surface methodology (RSM) was executed to evaluate the interactive effect of four process variables on the sorption of CV dye using Box-Behnken design. The quadratic model showed significance of model for the responses which were validated by analysis of variance (ANOVA). Maximum sorption (99.85%) of CV dye (2500 mg/L) was demonstrated on MLBC (800 °C) within 48 min of incubation at pH 8 and 47 °C temperature. The point of zero charge (pHpzc) and Brunauer-Emmett-Teller surfaces (BET) of MLBC were 7.7 and 168.23 m2 g−1, respectively. In addition, fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), total organic carbon (TOC) and atomic absorption spectroscopy (AAS) techniques were employed to characterize the biomass and MLBC. Toxicological studies of residual CV dye were executed using seed germination and tilapia fish model. Histological assessment of the gills showed no alterations in the gills architecture of fishes exposed to MLBC treated residual CV dye solution. Therefore, the present experimental results strongly revealed the strategies for utilizing low-cost biomass to treat waste water containing hazardous textile dyes.