Sustainable valorization of vinasse through plant based adsorbents for removing calcium, magnesium and potassium from waste

Vinasse is a distillery effluent with high fertilizer value; however, it is also one of the most polluting by-products due to its corrosivity, low pH, and high organic matter content making it 100 times more polluting than household sewage. Conventional treatment methods such as chemical coagulation with Alum (Al 2 (SO 4 ) 3 .14H 2 O), Ferric chloride (FeCl 3 .6H 2 O), Sodium aluminate, Aluminum chloride, and Ferric sulfate, have been widely applied, but these approaches often leave hazardous residues, increase treatment costs, and degrade soil and water quality. To address these limitations, this study explored sustainable alternatives by producing activated carbons from agricultural wastes-bagasse (BG), baobab shells (BB), and tamarind seeds (TS)-through phosphoric acid activation at temperatures ranging from 400 to 700 °C. The carbons were characterized using FTIR and proximate analysis, and their adsorption performance was tested under varying operational parameters, including pH, adsorbent dose, contact time, concentration, and agitation speed. Batch adsorption experiments revealed that equilibrium data fitted best with the Freundlich isotherm model, followed by Temkin and Langmuir, while adsorption kinetics followed a pseudo-first-order mechanism. Maximum removal of potassium (K + ), calcium (Ca 2+ ), and magnesium (Mg 2+ ) ions occurred at pH 10 to 12, with removal efficiencies of 98.22% for BG-AC, 97.21% for BB-AC, and 97.63% for TS-AC, demonstrating the effectiveness of these carbons in vinasse clarification. The study recommends pilot-scale trials to validate laboratory findings and assess scalability under real-world conditions. By valorizing agricultural residues into cost-effective adsorbents, this research enhances the economic value of by-products, reduces waste disposal challenges, and provides a sustainable source of activated carbon. Moreover, it contributes to achieving United Nations Sustainable Development Goals by improving water quality (SDG 6), promoting responsible production (SDG 12), supporting climate action (SDG 13), fostering green economic growth (SDG 8), and protecting ecosystems (SDG 15).