In-situ synthesis of efficient ZnCl2 doped pyrolyzed biochar for adsorptive remediation of organic dyes: Performance evaluation, mass transfer and mechanism

Effective management of harmful contaminants from waste effluent is crucial for a sustainable environment. Herein, the efficient adsorbent, sawdust-derived biochar doped with ZnCl2 (Z@SB) for removal of organic dyes, namely malachite green (MG) and methyl orange (MO), was explored via batch adsorption study. A detailed characterization of the synthesized adsorbent was conducted to determine its physiochemical properties. The specific surface area of Z@SB from BET analysis improved 5.66 times after chemical modification. Moreover, the decolorization efficiency of the dyes onto Z@SB was investigated through analyzing the impact of initial pH, adsorbent dose, and contact time of the process. The Langmuir isotherm analysis revealed the maximum adsorption capacity (Qmax) of MG and MO dyes were 318.47 and 225.73 mg/g, respectively. The adsorption kinetics data of both dyes was well described by the pseudo-second-order model. Furthermore, Boyd's film diffusion model was employed to assess the diffusion mechanism and determine the rate-limiting step using the kinetic data obtained from batch adsorption experiment. Possible mechanisms for the removal of dyes onto Z@SB included hydrogen bonding, pi-pi bonding, and electrostatic interactions. The superior regeneration and reusability properties observed in Z@SB make it a highly promising adsorbent for effective utilization in real-field wastewater treatment applications.