Organic-modified geopolymer nanosheet for efficient phosphorus removal from contaminated media and its potential...

High-performance, low-cost phosphate adsorbents with environmental compatibility and broad applicability are in high demand due to the limitations of existing materials, such as low adsorption capacity and high production costs. Inspired by the principle of "from nature, for purifying nature," a novel, cost-effective phosphate adsorbent based on fly ash and kaolin-derived geopolymer was developed. The material was organically modified via surfactant treatment to produce nanosheets with enhanced surface reactivity and active binding sites. The resulting adsorbent achieved a maximum phosphate adsorption capacity of 141.7 mg/g, significantly higher than that of the unmodified geopolymer (72.5 mg/g) and superior to most reported adsorbents. It also showed excellent performance across a wide pH range (5-8) and achieved 96.9 % phosphate removal from a 50 mg/L solution using only 0.8 g/L of adsorbent. The material demonstrated high efficiency in real water samples, including river, seawater, brackish, and tap water, reducing phosphorus levels to below 0.01 mg/L. CAL extraction tests (calcium-acetate-lactate method at pH 4) revealed that 25 % of the retained phosphorus was plant-available, indicating MEXGP potential for agricultural reuse as a slow-release fertilizer. Additionally, the use of low-cost industrial byproducts and minimal chemical inputs during synthesis ensures economic viability, with production costs significantly lower than those of commercial activated carbon and other synthetic adsorbents. These findings highlight the dual functionality of the developed geopolymer nanosheets (MEXGP): as an efficient adsorbent for wastewater treatment and as a phosphorus-enriched soil amendment, aligning with resource recovery and circular economy strategies. This study demonstrates a sustainable and scalable approach to phosphorus management, combining environmental remediation with nutrient reuse.