Efficient Removal of Acid Orange 7 Dye Using Acid-Activated Biochar Derived from Averrhoa Carambola: A Sustainable Approach for Wastewater Treatment

The aggregative release of harmful azo dyes into the environment has become a major concern due to their adverse impacts on ecosystems and human health. Among these dyes, Acid Orange-7 (AO7) has been identified as a persistent and toxic pollutant, necessitating effective treatment strategies for its removal from wastewater. In this study, an innovative and environment friendly method is introduced for the removal of AO7 dye utilizing acid-activated biochar (AAB) derived from the dried stem of Averrhoa carambola. The biochar is subjected to surface activation by acetic acid to enhance its surface area and porosity, optimizing its adsorption capacity. A comparative study through batch adsorption experiments was established to understand the removal potential of acid-activated biochar in removing AO7 dye. The effects of various parameters such as initial dye concentration, contact time, pH, and dosage of the biochar are studied to understand their influence on the adsorption process. Additionally, adsorption isotherms and kinetics models are employed to interpret the adsorption mechanism and rate. The results demonstrate that the AAB derived from Averrhoa carambola exhibits a higher adsorption capacity for AO7 dye, with removal efficiency of 98.5% with monolayer adsorption capacity of 39.7 mgg−1. The pH of the solution is found to significantly impact the adsorption process, with neutral conditions favoring better dye uptake. In addition, Langmuir model with better correlation coefficient in both the cases (unmodified and AAB) was found to be fitted better than Freundlich model suggesting monolayer adsorption. Moreover, the adsorption kinetics closely follow the pseudo-second-order model, suggesting chemisorption as the predominant mechanism. The AAB shows enhanced result than unmodified biochar due to its increased surface area, chemical modification, electrostatic attraction, pore filling, and chemisorption. Therefore, it holds a great potential for the removal of AO7 dye from wastewater, opening avenues for further research and practical implementation in water treatment technologies.