Sustainable removal of Acid Black 172 from wastewater using Lantana camara derived biochar insights from adsorption and statistical physics modeling

The discharge of dye-contaminated wastewater from textile and related industries represents a serious environmental concern due to the persistence, toxicity, and resistance of synthetic dyes to natural degradation. In this study, Lantana camara derived biochar (LCB) was investigated as a sustainable and low-cost adsorbent for the removal of Acid Black 172 (AB172) dye from aqueous solutions. The structural and surface properties of LCB were characterized using BET, FTIR, and HRTEM analyses, revealing a mesoporous structure with a surface area of 12.14 m² g⁻¹, pore diameter of 6.8 nm, and total pore volume of 0.031 cm³ g⁻¹. Batch adsorption experiments were conducted to evaluate the effects of pH, contact time, adsorbent dosage, and temperature. The adsorption process showed strong pH dependence, achieving maximum dye removal at pH 3, with equilibrium reached within 90 min. The Langmuir model predicted a maximum adsorption capacity of 303.03 mg g⁻¹, indicating a strong affinity between AB172 molecules and LCB surface sites. Kinetic analysis revealed that the adsorption followed a pseudo-second-order model, while thermodynamic parameters confirmed that the process is spontaneous and endothermic. In addition to this, the use of statistical physics modeling helped understand more about the adsorption process, such as adsorption orientation, adsorption energy, and the mechanism of surface interaction. These aspects set apart the study from other studies on adsorption. In the case of AB172 adsorption, the process was mainly influenced by electrostatic attraction, pore filling, van der Waals force, and hydrogen bonding interactions. Regeneration studies demonstrated high stability of the adsorbent, maintaining over 91% removal efficiency after five adsorption–desorption cycles. Statistical physics modeling and experimental studies on adsorption help in gaining a better insight into the processes involved in the dye-biochar interactions than traditional adsorption experiments do. These findings highlight LCB as a promising, environmentally sustainable, and economically viable adsorbent for the treatment of dye-contaminated wastewater.