Organic waste valorisation into biochar for the adsorptive removal of Malachite Green dye from its aqueous solution

This study illustrated the biochar utilization as an adsorbent to remove the Malachite Green (MG) dye which is known to cause toxic and hazardous effects. The present research aimed to determine how well biochar adsorbs malachite green dye and comprehend the fundamental principles driving adsorption. The iron-impregnated biochar was synthesized using waste biomass of Teak (Tectona speciose), which is a timber tree, by pyrolysis process at 500 °C. The synthesized biochar was used to remove MG dye from a synthetically prepared MG solution to evaluate its adsorption efficiency. The bioadsorbent was characterized using Particle Size Analysis (PSA), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), point of zero charges (pHZPC), Energy Dispersive X-ray (EDX). A batch adsorption experiment for the MG adsorption onto the MB-t surface was also conducted and it was found that the adsorption rate of MG was highly affected by the dose of biochar, temperature, working solution pH, time of contact and primary dye concentration. Isotherm study showed that the Temkin was the best-fit isotherm model to the adsorption process and the Qmax value was discovered to be 73.539 mg/g. Pseudo-second-order kinetics was best suited to the process of adsorption, indicating that the chemisorption was the rate-limiting factor. In contrast, the adsorption process was exothermic, which was determined through a thermodynamic study. The effective removal (89.05 %) of MG dye onto biochar (synthesized from Teak biomass the first time applied for dye removal) within 1 hr proved the bioadsorbent as a promising material for treating contaminated water.