Search

In this study, a novel adsorbent, MgO supported palygorskite, was synthesized by co-precipitation method and applied for simultaneous recovery of nutrients from wastewater. The synthesis parameters including MgO load ratio, calcination temperature, and calcination time were established and investigated. Several techniques, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Field-emission scanning electron microscope (FE-SEM) were employed to characterize the products at various synthesis conditions. A known concentration of simulated nutrients wastewater was used to optimize synthesis condition. The effects of adsorbent dosage, solution pH, and contact time on simultaneous recovery of nutrients were investigated under optimal condition (load ratio of 30%, calcination temperature of 400 °C, and calcination time of 4 h). 30%-MgO-PAL exhibited a strong removal capacities of ammonia nitrogen and phosphate in a wide pH range of 3–9, and the highest removal capacities of ammonia nitrogen and phosphate separately reached at 42.6 mg/g and 69.8 mg/g at pH of 9, dosage of 0.6 g/L, and contact time of 3 h. Both kinetics of ammonia nitrogen and phosphate followed the pseudo-second-order kinetic model. The mechanisms of nutrients recovery by MgO-PAL were extensively investigated.

In this study, struvite-humic acid loaded biochar/bentonite composite (HMCC), a recovery product of humic acid, nitrogen and phosphorus from biogas slurry, was prepared and used for simultaneous control of Zn(II) and antibiotic resistance genes (ARGs) pollution in manure-soil. The adsorption performance and mechanism of Zn(II) on HMCC were first studied in aqueous solution. The adsorption data fitted well to the Freundlich isotherm model, and the primary mechanisms of Zn(II) absorbed by HMCC involved the formation of Zn3(PO4)2·4H2O and humic acid-metal complex. The changes of Zn(II) content, antibiotic resistance genes (ARGs) and bacterial communities during the remediation of Zn(II) contaminated manure-soil were analyzed simultaneously. With HMCC amendment, the content of bio-available Zn(II) (bio-Zn) efficiently reduced from 847.4 mg/g to 739.2 mg/g and the total relative abundance of ARGs accordingly decreased by 37.18%. RDA analysis indicated that soil pH and bio-Zn were the main contributors to the fluctuations of soil ARGs. Spearman correlation analysis revealed that the potential hosts for ARGs mainly belonged to the phylum Actinobacteria. In addition, HMCC addition increased the diversity of bacterial community but significantly reduced the abundance of an antibiotic resistant bacteria-Actinobacteria. It is the first study to demonstrate the feasibility of HMCC as an environmentally friendly amendment to immobilize Zn(II) and mitigate the dissemination of ARGs in manure-soil.