Zhuoyao Fang,Kaizhen Zhang,Xiaolin Zhang,Bingcai Pan
Methylated arsenic species, including monomethyl arsenate (MMA) and dimethyl arsenate (DMA), are frequently detected in natural waters due to the biochemical methylation of arsenic and various human activities. The presence of MMA/DMA may cause excess total arsenic (>10 μg/L) in drinking water, yet the efficient removal of methylated arsenic still remains challenging. Herein, we reported the utilization of a recently developed nanocomposite HZO@N201 for selective removal of MMA and DMA from water. HZO@N201 contains the gel-type anion exchanger N201, i.e. , quaternary ammoniated poly(styrene-co-divinylbenzene) beads, as the host, and the embedded sub-5 nm hydrated zirconium oxide (HZO) for specific adsorption. In comparison with the commercially available nanocomposite HZO@D201, which was prepared through in-situ growth of HZO inside the macroporous anion exchanger D201, the adsorption capacities of HZO@N201 toward MMA and DMA ascended by ∼ 1.9 and ∼ 2.2 times, respectively, mainly benefitting from the sub-5 nm nature of HZO@N201. The competing anions including sulfate, chloride and bicarbonate exerted negligible impact on the removal efficiency toward MMA/DMA, due to inner-sphere complex formation between HZO NPs and MMA/DMA, as verified by SEM-EDS and XPS Zr 3d analysis. The exhausted HZO@N201 was fully regenerated by alkaline treatment for cyclic utilization without obvious efficiency loss. In fixed-bed experiments, HZO@N201 column was able to successively produce ∼ 4000 and ∼ 160 bed volume (BV) clean water from the feeding solutions containing MMA and DMA, while the values for HZO@D201 column were merely ∼ 1600 BV and ∼ 70 BV, respectively.
Advanced oxidation processes (AOPs) struggle to entirely remove phosphonates from wastewater, and the remaining phosphates easily cause secondary pollution. With MnFe 2 O 4 as the core and hydrated zirconium oxide (HZO) as the shell, the magnetic core-shell nanoreactor MnFe 2 O 4 @HZO with dual functions of "catalysis and adsorption" was designed to activate peroxymonosulfate (PMS) for nitrilotris-methylenephosphonic acid (NTMP) removal. Total phosphorus removal reached 96.5% within 180 min, with only 0.18 mg/L of phosphates left because of the full exploitation of active sites and adsorption sites. This is because of the strong inner-sphere complexation of shell for phosphates adsorption and the excellent electron transfer performance of the core for PMS activation. High NTMP removal under the protection of HZO shell could be obtained over wide pH (3−8) or complex water matrices. After five cycles, Mn leaching amount was only 0.4 mg/L. The study provides information on the design of core-shell catalysts in the PMS-AOP field for the comprehensive removal of contaminants.
Low temperatures were a critical factor that inhibited anaerobic ammonium oxidizing bacteria (AnAOB) activity. This study demonstrated the effect of exogenous zero-valent iron (ZVI) on Anammox-hydroxyapatite (HAP) system at 17°C. The results showed that long-term addition of ZVI increased the system nitrogen removal efficiency by 8.59% and alleviated the inhibition of AnAOB by low temperature. After addition of ZVI, the activity of AnAOB and the heme c content increased by 58.20% and 4.83%, respectively. Moreover, the functional enzyme activities of NIR, HZS, and HZO increased by 94.12%, 36.36%, and 16.67%, respectively. The concentrations of quorum sensing molecules, i.e., C 6 -HSL and C 8 -HSL, increased by 191.17% and 41.54%, respectively, after ZVI addition. Metagenomic analysis revealed that the addition of 5 g/L ZVI stimulated the relative abundance relative abundance of Fe(II) metabolism-related genes in AnAOB at 17 °C, thereby contributing to the uptake, transport, utilization, and storage of Fe(II). The addition of ZVI could improve the nitrogen removal performance of the anammox-HAP system at the low temperature.
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