Abstract
In this study, a novel system was set up by preparing a magnetic flocculant combining with ultraviolet/H2O2 to realize the rapid enrichment and degradation of diclofenac sodium (DCFS). For the magnetic flocculant, template anion polyacrylamide (TAPAM) with anion micro-block structure was prepared. Thereafter, polydopamine was used to modify TAPAM, Fe3O4 nanoparticles was grafted to the modified TAPAM by chelation, named template anion polyacrylamide-polydopamine-Fe3O4 (TAPAM-PDA-Fe3O4). Furthermore, the TAPAM-PDA-Fe3O4 preparation protocol was optimized by the response surface method (RSM). In the DCFS enrichment section, the rapid separation of flocs from water was realized by an external magnetic field and it indicated that the π–π stacking effect was dominant in neutral/alkaline condition, whereas charge neutralization was favored in acidic conditions. Meanwhile, a DCFS enrichment kinetic curve was much fitted by the pseudo-second-order kinetic model and DCFS enrichment isothermal curve was close to the Freundlich isothermal model, indicating the dependence of DCFS quantity enriched by TAPAM-PDA-Fe3O4 and a multilayer heterogeneous enrichment process. The degradation experiment confirmed that DCFS was effectively degraded by ultraviolet/H2O2/TAPAM-PDA-Fe3O4 and the maximum value of DCFS degradation efficiency reached 98.1%. Furthermore, the regeneration experiment showed that the enrichment and degradation efficiency of DCFS could maintain a relatively high level in the initial three recycles.
Highlights
Diclofenac sodium (DCFS) represents a rising concern due to its ecotoxicological potential and current, sustained release into the aquatic environment
template anion polyacrylamide (TAPAM)-PDA-Fe3 O4 was successfully prepared to achieve a high-level enrichment of diclofenac sodium (DCFS), up to 99.1%
The rapid separation of flocs from aqueous environment was realized by external magnetic field and higher maximum removal efficiency could be achieved with TAPAM-PDA-Fe3 O4 (99.1%) instead of APAM-Fe3 O4 (49.0%) or TAPAM-Fe3 O4 (66.2%)
Summary
Diclofenac sodium (DCFS) represents a rising concern due to its ecotoxicological potential and current, sustained release into the aquatic environment. Many regions and countries, such as Europe, America, China, and so on, have added DCFS to the priority substances monitoring list of water policy [1,2,3]. A hundred tons of DCFS are sold annually worldwide, about 15%. Of which is excreted unchanged by human race and is frequently detected in domestic wastewater [4]. The ever-increasing global population is expected to cause a sharp increase in the emissions of DCFS in the future. Several studies have shown that DCFS exposure demonstrates bioaccumulation in invertebrates, which has an ecotoxicological risk to the aquatic food chain [5]. Due to the Polymers 2020, 12, 72; doi:10.3390/polym12010072 www.mdpi.com/journal/polymers
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