Towards greener water remediation: Ca-impregnated pyro-hydrochar of spent mushroom substrate for enhanced adsorption of acridine red and methylene blue

Abstract

Sustainable solutions for environmental remediation are of great interest due to the escalated release of toxic substances into the ecosystem. Here, Ca-impregnated pyro-hydrocarbon (Ca-SMS) was synthesized from spent mushroom substrate (SMS) via hydrothermal carbonization at a relatively low process temperature, followed by subsequent physicochemical activation. Ca-SMS underwent characterization using various analytical techniques, and its efficacy in removing acridine red (AR) and methylene blue (MB) was assessed through batch experiments. The results suggested that Ca-SMS is an effective adsorbent for AR and MB, visiting a removal capacity of 33.82 and 81.98 mg g−1 at 35 °C, respectively. The kinetic investigation uncovered that the dye removal process mostly agreed with the pseudo-second-order (PSO), while the Langmuir and Freundlich models were the most suitable to describe the removal of dyes. Thermodynamic analyses showed that the remediation process is spontaneous and endothermic. Adsorption mechanisms among dyes and Ca-SMS were multiple: physical adsorption, surface complexation, electrostatic, and π-π interaction. The feasibility of the proposed method for real sample treatment was demonstrated. These findings indicate that Ca-SMS is an effective alternative sorbent for the remediation of textile wastewater and is a viable solution for waste reduction in the rising mushroom cultivation sector.