Degradation of 4-nonylphenol in marine sediments using calcium peroxide activated by water hyacinth (Eichhornia crassipes)-derived biochar.

The contamination of marine sediments by 4-nonylphenol (4-NP) has become a global environmental problem, therefore there are necessaries searching appropriate and sustainable remediation methods for in-situ applications. Herein, water hyacinth [(WH) (Eichhornia crassipes)]-derived metal-free biochar (WHBC) prepared at 300-900 °C was used to promote the calcium peroxide (CP)-mediated remediation of 4-NP-contaminaed sediments. At [CP] = 4.37 × 10 M, [WHBC] = 1.5 g L, and pH = 6.0, the degradation of 4-NP was 77% in 12 h following the pseudo-first order rate law with rate constant (k) of 4.2 × 10 h. The efficient 4-NP degradation performance and reaction mechanisms of the WHBC/CP system was ascribed to the synergy between the reactive species (HO• and O) at the WHBC surface on which there were abundant electron-rich carbonyl groups and defects/vacancies in the catalyst structure provides active sites, and the ability of the graphitized carbon framework to act as a medium for electron shuttling. According to microbial community analysis based on amplicon sequence variants, bacteria of the genus Solirubrobacter (Actinobacteria phylum) were dominant in WHBC/CP-treated sediments and were responsible for the biodegradation of 4-NP. The results showed great promise and novelty of the hydroxyl radical-driven carbon advanced oxidation processes (HR-CAOPs) that relies on the value-added utilization of water hyacinth for contaminated sediment remediation in achieving circular bioeconomy.