A multifunctional fertilizer for long-term release and remediation of Cr(VI)-polluted soil: Dialdehyde CMC urea-formaldehyde grafted on nZVI@MOF(Mg)-74

Abstract

Excessive use of chemical fertilizers and their loss have resulted in low utilization efficiency of nutrient and the heavy metal pollution of soil. To solve these problems, the multifunctional fertilizer (nZVI@MOF-g-DCUF) was prepared and characterized, using nanoscale zero-valent iron-doped MOF(Mg)-74 (nZVI@MOF) as the core and a dialdehyde carboxymethylcellulose urea-formaldehyde (DCUF) as the coating. The addition of nZVI@MOF-g-DCUF improved the water retention capacity of the soil. The cumulative release ratios (Cr%) of nZVI@MOF-g-DCUF2.0, nZVI@MOF-g-DCUF1.0, nZVI@MOF-g-DCUF0.5, and nZVI@MOF-g-DCUF0.25 in soil were respectively 96.72 %, 93.68 %, 90.67 %, and 82.75 % at the 35th day, which confirmed the long-term release of nZVI@MOF-g-DCUF. In subsequent pot experiments, nZVI@MOF-g-DCUF exhibited a positive effect on the growth of Chinese cabbage. The results of soil remediation showed that the Cr(VI) removal ratio of soil with adding 1 % (wt%) of nZVI@MOF-g-DCUF2.0 and nZVI@MOF-g-DCUF1.0 were 84.40 % and 76.83 %, respectively, indicating a significant remediation effect on Cr-polluted soil. The mechanism of soil remediation indicated that the Cr(VI) immobilization on nZVI@MOF-g-DCUF via H-bonding, reduction, precipitation, and complexation. Therefore, the proposed materials are promising fertilizers for the long-term release of nutrients and immobilization of Cr(VI) in polluted soil.