Adsorptive Remediation of Cadmium Ions with Modified Plant Straw Using Response Surface Methodology
摘要
The prevalence of heavy metal contaminants in wastewater poses a profound threat to both human well-being as well as environmental health, obliging the introduction of proficient and environmentally friendly remediation techniques. Our current study implemented RSM (Response Surface Methodology) based Box-Behnken design for optimising the operating factors encompassing temperature, adsorbent amount, and solution pH, which govern the cadmium adsorption. The optimal conditions for attaining a highly desirable solution of maximum cadmium adsorption (Desirability = 0.985) were 38 °C temperature, a 5.07 solution pH, and a 12 g L−1 adsorbent dose. Given these optimal conditions, the adsorption efficiency of cadmium was recorded as 76.39% for raw rice straw, 91.84% for acid-modified rice straw, and 79.87% for bio-modified rice straw. These values closely aligned with those obtained through the Box-Behnken design, indicating a consistent and reliable outcome. The thermodynamic study of cadmium adsorption revealed that the process was thermodynamically feasible as well as spontaneous (ΔG = − ve). In addition, the cadmium removal by raw and modified rice straw was endothermic in nature (ΔH = + ve). The adsorption process aligned with the Langmuir adsorption isotherm with an R-squared value of 0.99 and pseudo-second-order kinetics with an R-squared value of 0.99. Further, acid-modified rice straw exhibited the highest adsorption efficiency compared to the bio-modified rice straw and the raw rice straw, indicating a significant enhancement in its effectiveness on account of adsorbent modification. The adsorption capability of raw and modified rice straw decreased across three adsorption–desorption cycles; however, the reusability for cadmium removal reflected the absorbent's economic viability and suitability for commercial application. The overall findings strongly indicate that employing rice straw as a sustainable and competent biosorbent is highly feasible for effectively treating cadmium-embraced wastewater. In addition, the employment of rice straw as a biosorbent contributes to waste valorization and promotes circular economy values through waste valorization for wastewater treatment. This research introduces an eco-friendly and sustainable approach to removing heavy metals, aiming to minimize the environmental impact of water purification.