Fertilizer-infused novel GO-alginate-polyacrylic acid hydrogels for groundwater extraction in irrigation applications

Superhydrophilic hydrogels are synthesized and infused with fertilizer for effective groundwater extraction. Firstly, the synthesis of alginate-polyacrylic acid hydrogels (H1, H2, and H3) was optimized by using an organic crosslinker and an initiator at different concentrations; then the synthesized hydrogels were tested for deionized (DI) water production. The H1 hydrogel showed the highest water production of 20 ± 1.6 mL and was selected for further experimentation. Afterward, graphene oxide (GO) was incorporated into the H1 hydrogel to fabricate hydrogels HG1 and HG2. It was found that HG1 hydrogel achieved higher water production at 33 ± 1.1 mL, compared to the H1 hydrogel without GO, the addition of GO enhanced the hydrogel's water production performance by 65 %. Furthermore, the HG1 hydrogel was soaked in concentrate fertilizer solutions of KCl and KNO₃, respectively, to increase hydrogel's inner salinity and osmotic pressure. In the groundwater desalination experiments, the KCl-infused hydrogel produced 39 ± 2.0 mL of diluted fertilized water, which was 30 % higher than that of the KNO₃-infused hydrogel. Moreover, the HG1 hydrogel achieved 99.9 % removal of Mg²⁺ and Na⁺ and 96.2 % of Ca²⁺, while the concentration of the K⁺ in the treated water was enriched by 7.7 times; such nutrient-rich water was suitable for agricultural fertigation. The superhydrophilic GO-alginate-polyacrylic acid-GO hydrogel could be used as a novel drawing agent for energy-efficient desalinating brackish groundwater and producing fertilized water for agriculture applications.