Synthesis of semicoke-based geopolymers as delivery vehicles for slow release of herbicides

Abstract

Semicoke (SC) is a kind of powder of industrial by-products that easily cause environmental pollution due to the presence of stable organic matter in clay minerals. In this work, a porous magnetic semicoke-based geopolymer (MSC-GP) was prepared using SC as the raw material. Then, 2-methyl-4-chlorophenoxyacetic acid (MCPA), a typical herbicide, was loaded into the porous MSC-GP and composited with sodium alginate (SA) using calcium as a crosslinking agent, which afforded MSC-GP/SA encapsulating MCPA (MCPA@MSC-GP/SA). The structure and micromorphology of SC, SC-GP and MCPA@MSC-GP/SA were characterized by FT-IR spectroscopy, TG-DTG, SEM and EDS. After measuring the swelling behavior in water and saline solutions, the water retention capacity, pH effect, degradation efficiency, site-specific targeted release, recovery, slow-release behavior, and pot experiments of MCPA@MSC-GP/SA were assessed. This indicated that the water retention capacity of soils was improved by the addition of MCPA@MSC-GP/SA. The release rate of the herbicide in MCPA@MSC-GP/SA was 65.2% in 90 days, which indicated that MCPA@MSC-GP/SA possessed a higher utilization efficiency and control of weeds compared to traditional herbicide. In summary, this study opens up a new avenue for improving the utilization efficiency of SC and prolonging the duration of herbicide action, which may have potential applications in agricultural production.