Development of Biochar Based Nanocomposites for Wastewater Purification

Abstract

Industrial effluents being released into water reservoirs play a significant role in environmental pollution, even minute quantities of these noxious industrial pollutants cause serious health hazards. In this respect, nanotechnology in adsorption followed an ecofriendly and low capital technique in order remediate polluted water. The current research was conducted to remove Reactive Blue 19 dye (RB19D), Tartrazine dye (TD), Phosphate (PO4 -3 ) and Nitrate (NO3 - ) in a fixed bed column and batch mode by biochar based iron (Fe), zinc oxide (ZnO), zirconium ferrite (ZrFe2O5), graphene oxide/zirconium ferrite (GO/ZrFe2O5) and graphene oxide (GO) nanocomposites using sorption technology. The effect of various operating parameters i.e. pH, concentration, sorbent dose, temperature and contact time were examined for maximum removal of RB19D, TD, PO4 -3 and NO3 - . The optimum conditions for environmental variables for maximum sorption of these selected organic and inorganic pollutants were observed to be pH 2, sorbent dose 0.1 g/50mL, 50 mg/L concentration, 120 min equilibrium time and 30 ºC temperature. Various equilibrium and kinetic models were applied on experimental data to explain the mechanism and rate of sorption process. Freundlich sorption isotherms and pseudo second order kinetics model were fitted best on sorption data. Thermodynamics parameters were studied to apprehend the feasibility and spontaneity of sorption phenomena. The impact of interference of heavy metals ion, electrolytes and surfactants on sorption potential of sorbents for dyes and inorganic ions removal was also evaluated. The regeneration/desorption study revealed the highest recovery of sorbents was attained using 0.5 M NaOH as an eluent. In continuous mode experiments, optimum inlet concentration, flow rates and bed height were observed to be 50 mg/L, 1.8 mL/min, and 3 cm respectively for highest removal of dyes and inorganic ions. Central composite statistical design (CCD) using response surface methodology was employed to explore independent variables impact such as pH, concentration and adsorbent dose to determine optimum conditions for elimination of dyes (RB19D and TD) and inorganic ions (PO4 -3 and NO3 - ). The significance of experimental data was evaluated by R2 and p value of analysis of variance (ANOVA). Sorption study was also conducted on real textile and fertilizer effluents for application of this technology on practical scale to efficiently remove COD. The characterization of synthesized nanomaterial was done using UV/Vis Spectroscopy to monitor synthesis, XRD to investigate crystalline nature of nanocomposites, FTIR for recognition of functional groups involve in adsorption, SEM showed surface morphology and EDX for determination of elemental composition. Nanoparticles and nanocomposites were also evaluated for their antioxidant, antibacterial (gram positive; B. subtilis and gram negative; E. coli), antifungal (S. commune and A. niger) and heamolytic potential. The results revealed that nanoparticles possessed excellent antioxidant, antimicrobial potentials and least cytotoxicity while biochar based nanocomposites showed poor antimicrobial activities. Among all samples graphene oxide was found most cytotoxic