Adsorptive and fertilizing potential of waste plasterboard for sustainable phosphorus management

Phosphorus (P) is vital for plant growth, yet its imbalance across ecosystems poses major environmental and agricultural challenges. Excess P in water leads to eutrophication, while soil deficiency restricts crop productivity. To address both issues, this study explored a sustainable strategy using waste plasterboard (WPB), a gypsum-based construction by-product, as a dual-purpose material. WPB was used to remove P from aqueous solutions, and the P-loaded WPB (P–WPB) was subsequently assessed as a phosphorus source for rice cultivation. Contrary to other calcium-rich adsorbents primarily composed of CaCO 3 , thermal treatment of CaSO 4 -based WPB resulted in a decline in P adsorption capacity. The superior adsorption performance of untreated WPB was likely associated with its rougher surface morphology, higher calcium elution, and active surface functionalities (C O and –OH groups). P adsorption was diminished under acidic conditions but notably enhanced by the presence of carbonate ions (CO 3 2- ). The adsorption of P onto WPB was characterized as an endothermic, monolayer interaction. The maximum adsorption capacity of the WPB was 218.18 mg/g. Environmental safety of the WPB was confirmed through toxicity characteristic leaching procedure and Daphnia magna assays, which showed low toxicity and heavy metal levels below regulatory limits for both WPB and P–WPB. In rice growth experiments, medium and high application levels of P–WPB significantly improved plant growth, demonstrating comparable or superior performance to conventional commercial fertilizers. This study presents a sustainable and cost-effective approach for P removal and recovery using WPB, contributing to water purification, waste recycling, and sustainable P management. • Waste plasterboard (WPB) achieved high phosphorus adsorption capacity (218.18 mg/g). • WPB adsorbed P via Ca precipitation and C O and –OH groups. • Phosphorus removal was enhanced by alkaline pH and carbonate ions (CO3 2- ). • Phosphorus-loaded WPB effectively replaced commercial fertilizer in rice cultivation. • WPB provides a sustainable approach to waste reuse and phosphorus recycling.