Cadmium(II) adsorption by recyclable Zeolite-Loaded Hydrogel: Extension to the removal of Cadmium(II) from contaminated soil

Excessive cadmium(II) (Cd(II)) in soil has gravely jeopardized global ecosystem stability and human health. The removal of Cd(II) is a permanent cure to remediate Cd(II)-contaminated soil. Herein, a recyclable removal material, zeolite@cellulose-poly(acrylamide) hydrogel (Z@CA) was developed. Batch adsorption experiments and characterisations (SEM-EDS, FTIR, XRD, and XPS) were conducted to explore the adsorption capacity and mechanism of Z@CA. A pot experiment was established to evaluate the effect of Z@CA on soil Cd(II) remediation and Cd(II) toxicity in water spinach. The results showed that in aqueous solutions, the maximum adsorption capacity of Cd(II) by Z@CA was 84.4 mg·g−1. Electrostatic attraction, ion exchange, and surface complexation collectively facilitated Cd(II) capture by Z@CA. Even after five adsorption–desorption cycles, Z@CA maintained a Cd(II) removal efficiency of 89.88 %. The results of the pot experiment showed that after applying Z@CA (2.5 w/w) in soil for 21 days, the content of bioavailable Cd(II) and total Cd(II) significantly decreased by 59.38 % and 1.75 %, respectively. The recovery rate of Z@CA reached 94.77 % and maintained its original intact structure. In addition, the Cd(II) content of water spinach was reduced by 91.43 % compared to the treatment without Z@CA, the weight, height, and relative chlorophyll content reaching 1.34, 1.73, and 1.49 times that of the treatment without Z@CA. The ideal application of Z@CA provides novel approaches and insights into the remediation of Cd(II)-contaminated soils.