A Study on Adsorption Kinetics and Isotherms of Heavy Metals on Sawdust and Optimization

The discharge of heavy metals in the effluents of chemical industries poses environmental hazards due to their carcinogenic, mutagenic, and toxic properties. The stringent discharge limits imposed by regulatory agencies pose a challenge for conventional chemical degradation processes to meet the required standards. Physicochemical techniques, specifically adsorption, provide a pragmatic and economical resolution. This analysis specifically examines the process of adsorption, which involves the attachment of copper, nickel, and chromium to sawdust. Batch experiments were carried out with an initial concentration of 10 parts per million (ppm) for each adsorbate. The Freundlich isotherm is the most accurate representation of the adsorption of heavy metals Ni and Cr, compared to the Langmuir and Dubinin–Radushkevich isotherms. This conclusion is supported by a high R² value (>0.90). On the other hand, the adsorption of Cu follows the Dubinin–Radushkevich isotherm, as indicated by its R² value of 0.98. Although both the Lagergren pseudo-first-order and second-order kinetic models are appropriate for fitting the data, the latter exhibits superior performance. Stirrer speeds exceeding 100 rpm have no substantial effect on removal efficiency. The response surface method (RSM) was used to create an optimized model that represents the intercorrelation between factors that impact adsorption performance.