Qiang Li

To resource utilization of the spent cation exchange resin, the carbonized resin with Fe doping (Fe3O4@CR) was prepared to activate persulfate (PS) for the degradation of oxytetracycline (OTC). Fe3O4@CR exhibited high catalytic potential for the degradation of OTC with relatively low activation energy (Ea = 28.86 kJ/mol). In the Fe3O4@CR/PS system, 76.4% of the OTC was removed under the conditions ([PS]: 0.15 g/L, [Fe3O4@CR]: 0.3 g/L, T: 25ºC). Fe3O4@CR could work effectively for activating PS to degrade OTC in the pH range of 3.0-7.0. The free radical quenching experiments and electron paramagnetic resonance (EPR) analysis showed that •OH and SO4•- were the main radicals for the degradation of OTC. The conversion between Fe3+ and Fe2+ accelerated the degradation of OTC by generating •OH and SO4•-. The possible degradation pathways were proposed. The OTC was mineralized to smaller molecules, such as C14H10O3 and C7H11O. This study offers a new perspective on waste resin recycling and water purification.

In this study, Congo red (CR) was degraded by different particle sizes of zero-valent copper (ZVC) activated persulfate (PS) under mild temperature. The CR removal by 50 nm, 500 nm, 15 μm of ZVC activated PS was 97%, 72%, and 16%, respectively. The co-existence of SO₄^2- and Cl^- promoted the degradation of CR, and HCO₃^- and H₂PO₄^- were detrimental to the degradation. With the reduction of ZVC particle size, the effect of coexisting anions on degradation grew stronger. The high degradation efficiency of 50 nm and 500 nm ZVC was achieved at pH=7.0, while the high degradation of 15 μm ZVC was achieved at pH=3.0. It was more favorable to leach copper ions for activating PS to generate reactive oxygen species (ROS) with the smaller particle size of ZVC. The radical quenching experiment and electron paramagnetic resonance (EPR) analysis indicated that SO₄^-•, •OH and •O₂^- existed in the reaction. The mineralization of CR reached 80% and three possible paths were suggested for the degradation. Moreover, the degradation of 50 nm ZVC can still reach 96% in the 5th cycle, indicating promising application potential in dyeing wastewater treatment.

Extensive use of antibiotics in the world will cause potential risks to human health and ecosystems. The removal of these antibiotics has attracted much attention. Composite materials are growing attention for diverse pollutants separation and removal based on their specific functionality and surface area. In this study, a series of N-vinylpyrrolidone-divinylbenzene polymers (NVPD) with different N-vinylpyrrolidone (NVP) contents were facilely prepared for the adsorption of tetracycline (TC). The effect of polymer surface properties and aqueous solution chemistry (pH, ionic strength, humic acid) on TC adsorption was further studied. The dynamic adsorption and regeneration experiments were also assessed. The results showed that only 25% of NVP was involved in the reaction. When NVP dosage (%) was 75%, polymer (NVPD-g) owned the largest BET surface area (613.23 m²/g) and obtained the maximum TC adsorption capacities (258.76 mg/g). In the kinetic, the adsorption between TC and polymers with NVP was controlled by chemical adsorption and intra-particle diffusion. The TC adsorption process of NVPD-g depended on the contribution of the hydrophobic effect, electrostatic interactions, H-bonding, π-π electron donor–acceptor (EDA) interactions, and cation-π bonding. Moreover, the removal efficiency of TC by NVPD-g was enhanced in the presence of humic acid (HA) in the dynamic adsorption and 1197 BV (2394 mL) of TC simulated wastewater can be treated. These findings suggest that NVPD-g has a potential application in the purification of TC.

Oxytetracycline (OTC) is a typical antibiotic that poses a serious threat to the environment. However, traditional treatment methods suffer from low treatment efficiencies and potential secondary contamination. Therefore, there is a need to develop efficient, convenient, and environmentally friendly removal technology. In this paper, magnetic nano-Cu/Fe composites were successfully synthesized and used as the activator of peroxymonosulfate (PMS) to degrade OTC. The obtained catalysts with different ratios showed excellent degradation effects, especially the Cu/Fe-1 catalysts. The highest removal efficiency of OTC (93%) was achieved with 0.2 g L⁻¹ PMS and 0.1 g L⁻¹ catalyst in 60 min. The impacts of the catalyst and PMS dosages, initial temperature and pH, coexisting anions, microplastics, and real-life water samples were investigated. To explore the mechanism for OTC degradation, radical scavenging and electron spin resonance (EPR) experiments were carried out, and non-radical ¹O₂ was identified to be the main radical. TEM and XRD results show the presence of CuFe₂O₄ composites in Cu/Fe-1, which can promote the production of ¹O₂ and thus improve the OTC degradation efficiency. This work provides a new efficient, stable, low-cost, and environmentally friendly approach for the degradation of oxytetracycline.

Biochar emerged as a promising material due to its high efficiency and tunable physicochemical properties. In order to improve the economic applicability of biochar catalysts, we attempted to apply formed Cu-doped deactivated magnetic loofah biochar (Cu-Fe-LBC) as a peroxymonosulfate (PMS) activator to remove tetracycline (TC). The catalyst exhibited high activation of PMS and high stability with the TC removal of 97.6%. The chemical composition and groups on the catalyst surface confirmed the presence of copper ions on the biochar by complexation with COO–. Analysis of quenching experiments and electron paramagnetic resonance indicated the significance of HO˙ and ¹O₂ in TC degradation. The catalytic system had high catalytic efficiency with a wide pH range and coexisting anions. The possible degradation mechanism was proposed. Moreover, the research provides an insight into the PMS activation by reusing waste biochar catalysts.

Nowadays the market value and scope of the Light-Emitting Diode (LED) industry are increasing and the amount of waste in the process has also increased. The wastewater containing gallium (Ga) ion is also produced in the LED process, such as etching, washing, and grinding. This gallium element was very rare and valuable on the earth. In this study, the agricultural waste of pomelo peel was used to be the bioadsorbent to recycle the gallium from the gallium ion wastewater to achieve the purpose of the use of waste to recycle. According to the bioadsorption tests, the use of hydrochloric acid modified bioadsorbent of pomelo peel could achieve 96.80 % bioadsorption efficiency under the optimized condition found in this study.