Comparative study of organic removal by pre-adsorption oxidation and synchronous adsorption oxidation processes: Performance and mechanism.

Both adsorption and oxidation occur and contribute to organics removal in carbonaceous materials based advanced oxidation processes, while the correction of adsorption and oxidation, and the role of adsorption in the veritable removal of organic are not clear. Herein, we investigated the performance of carbamazepine (CBZ) removal by peroxymonosulfate (PMS) activated by magnetic Fe-doped biochar through two models of pre-adsorption oxidation and synchronous adsorption oxidation processes. The adsorption process was better fitted by pseudo-second-order kinetic model and the adsorption mechanism was obtained by comprehensive analysis of equilibrium adsorption capacities, surface functional groups, specific surface area, pore volume, and ID/IG value. It is noted that pre-adsorption highly inhibited the further oxidation of CBZ in 0.5Fe@LSBC700/PMS system due to the occupied catalytic active sites. Total CBZ removal in pre-adsorption oxidation (45 %) was inferior to synchronous adsorption oxidation (∼100 %), as well as the veritable CBZ oxidation removal of 27 % for pre-adsorption oxidation vs ∼100 % in synchronous adsorption oxidation at 30 min. Oxidation degradation of CBZ based on radical oxidation was identified by quenching experiments and electron paramagnetic resonance measurements. This work is conducive to identifying the role of adsorption during the removal of organics in the adsorption-oxidation process, as well as veritable adsorption and oxidation removal of organics.

Effective oxidation and adsorption of As(III) in water by nanoconfined Ce-Mn binary oxides with excellent reusability.

Herein, a highly efficient As(III) purifier Ce-Mn@N201 with excellent reusability was developed by stepwise precipitating hydrated cerium(IV) oxides (HCO) and hydrated manganese(IV) oxides (HMO) inside N201, a widely-used gel-type anion exchange resin. Owing to confinement of unique nanopores in N201, the in-situ generated nanoparticles (NPs) inside Ce-Mn@N201 were highly dispersed with ultra-small sizes of around 2.6 nm. Results demonstrated that HMO NPs effectively oxidized As(III) to As(V) with the conversion of Mn(IV) to Mn(II), while the generated Mn2+ was mostly re-adsorbed onto the negatively-charged surface of HMO NPs. During the regeneration process by simple alkaline treatment, the re-adsorbed Mn2+ was firstly precipitated as (hydr)oxides of Mn(II) and then oxidized to HMO NPs by dissolved oxygen to fully refresh its oxidation capacity. Though HCO NPs mainly served as adsorbent for arsenic, they could partially oxidize As(III) to As(V) at the beginning, while the oxidation capacities continuously diminished with the irreversible conversion of Ce(IV) to Ce(III). In 10 consecutive adsorption-regeneration cycle, Ce-Mn@N201 efficiently decontaminated As(III) from 500 µg/L to below 5 µg/L with Mn2+ leaching less than 0.3% per batch. During 3 cyclic fixed-bed adsorptions, Ce-Mn@N201 steadily produced 8500-9150 bed volume (BV) and 3150-3350 BV drinkable water from the synthesized and real groundwater, respectively, with Mn leaching in effluent constantly < 100 µg/L.

Restricted reaction of layered double hydroxide nanoparticles with phosphate in a confined microsphere space.

Over the past decades, considerable efforts have been made to find useful solutions for phosphate pollution control. The state transition of nanomaterials from freely dispersed to encapsulated provides a realizable route for their application in phosphate elimination. The separation convenience offered by encapsulation has been widely recognized, however, the unique binding mode of nanostructures and phosphate in the confined space remains unclear, limiting its further development. Here, carboxymethyl cellulose (CMC) microspheres were used as hosts to deploy layered double hydroxide (LDH) nanoparticles. On this basis, we described an attempt to explore the adsorption behavior of LDH and phosphate in the microsphere space. Compared to their freely dispersed analogues, LDH particles exhibited higher structural stability, wider pH adaptability, and better phosphate selectivity when spatially confined in the CMC microsphere. Nevertheless, the kinetic process was severely inhibited by three orders of magnitude. Besides, the saturated phosphate adsorption capacity was also reduced to 74.6 % of the freely dispersed system. A combinative characterization revealed that the highly electronegative CMC host not only causes electrostatic repulsion to phosphate, but also extracts the electron density of the metal center of LDH, weakening its ability to act as a Lewis acid site for phosphate binding. Meanwhile, the microsphere encapsulation also hinders the ion exchange function of interlayer anions and phosphate. This study offers an objective insight into the reaction of LDH and phosphate in the confined microsphere space, which may contribute to the advanced design of encapsulation strategies for nanoparticles.

Effect of bromide on molecular transformation of dissolved effluent organic matter during ozonation, UV/H2O2, UV/persulfate, and UV/chlorine treatments.

Ozonation and ultraviolet-based advanced oxidation processes (UV-AOPs) play important roles in advanced treatment of municipal wastewater for water reuse. Bromide is widely present in wastewater at different concentration levels (ranging from µg/L to mg/L). However, the effect of bromide on molecular transformation of dissolved effluent organic matter (dEfOM) in real wastewater during ozonation and UV-AOPs treatments still remains unclear. Herein, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) was utilized to characterize the overall molecular transformation of dEfOM and the formation of unknown halogenated byproducts (X-BPs) in ozonation, UV/H2O2, UV/persulfate (UV/PS), and UV/chlorine (UV/Cl) processes in the presence of additional bromide. Compared with the same oxidation processes without additional bromide, the degree of dEfOM oxygenation had some extent decrement with the effect of bromide. A slightly increment of the number of unknown brominated byproducts (Br-BPs) was observed during ozonation, UV/H2O2, and UV/PS treatments in the presence of additional bromide, and the largest increment of these compounds was found in UV/Cl process. A total of 82 chlorinated byproducts (Cl-BPs) and 183 Br-BPs were detected in all oxidation processes with the effect of bromide, and the number of Br-BPs was significantly higher than that of Cl-BPs. Based on mass difference analysis, 69 pairs of possible precursors/Br-BPs were identified. In addition, the additional bromide did not remarkably increase the concentrations of trihalomethanes (THMs) and haloacetic acids (HAAs) in ozonation, UV/H2O2, and UV/PS treatments, while the production of THMs and HAAs significantly decreased by 68.06% and 54.55%, respectively, during UV/Cl treatment. The calculated cytotoxicity increased to some extent for each treatment, especially for UV/Cl treatment, and the compound with largest contribution to cytotoxicity was monobromoacetic acid. This study provides new insights into the formation and transformation of X-BPs during advanced treatment of real wastewater with the effect of bromide.

Unravelling molecular transformation of dissolved effluent organic matter in UV/H2O2, UV/persulfate, and UV/chlorine processes based on FT-ICR-MS analysis.

Ultraviolet-based advanced oxidation processes (UV-AOPs) are very promising in advanced treatment of municipal secondary effluents. However, the transformation of dissolved effluent organic matter (dEfOM) in advanced treatment of real wastewater, particularly at molecular level, remains unclear. In this study, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) coupled with multiple statistical analysis were performed to better understand the transformation of dEfOM in UV/H2O2, UV/persulfate (UV/PS), and UV/chlorine treatments. An obvious increase in oxygen content of dEfOM was observed after every UV-AOPs treatment, and the detailed oxygenation processes were further uncovered by mass difference analysis based on 24 types of typical reactions. Generally, UV/H2O2 process was subjected to the most oxygenation reactions with the typical tri-hydroxylation one (+3O), whereas di-hydroxylation reaction (+H2O2) was dominant in UV/PS and UV/chlorine processes. Additionally, the three UV-AOPs shared the majority of precursors, and more proportions of unique products were identified for each process. The precursors with lower H/C and higher aromaticity were readily degraded by UV/chlorine over UV/H2O2 and UV/PS, with the products featuring lower molecular weight. Moreover, dEfOM of high aromaticity tended to produce chlorinated byproducts through addition reactions in chlorination and UV/chlorine processes. Among these UV-AOPs, the highest reduction of both acute toxicity and specific UV absorbance at 254 nm (SUVA254) was observed for UV/chlorine, implying the potential for UV/chlorine process in advanced treatment of wastewater. In addition, acute toxicity was highly correlated with SUVA254 and CHOS compounds. This study is believed to help better understand the different fates of dEfOM in real wastewater during UV-AOPs treatment.

Enhanced removal of arsenic from water by using sub-10 nm hydrated zirconium oxides confined inside gel-type anion exchanger.

Given high selectivity and excellent stability, zirconium oxides are very promising in selective removal of arsenic, fluorine, and phosphorus from water. Nevertheless, it remains challenging to prepare sub-10 nm zirconium oxides of ultra-high adsorptive reactivity. Herein, we prepared hydrated zirconium oxides (HZO) of 4.88 ± 1.02 nm by conducting in-situ precipitation of nanoparticles (NPs) inside the gel-type anion exchanger (GAE). GAE was swollen in water and contained lots of < 10 nm swollen pores, restricting excess growth of HZO NPs. In comparison, the NPs formed inside the macroporous anion exchanger (MAE) possessed an average diameter of 30.91 ± 8.98 nm. XPS O1s analysis indicated that the oxygen sites in the gel-type nanocomposite (HZO@GAE) possessed a much higher proportion (48.9%) of reactive terminal oxygen (-OH) than the macroporous nanocomposite (HZO@MAE, 21.2%). Thus, HZO@GAE exhibited significantly enhanced adsorption reactivity toward As(V)/As(III) than HZO@MAE. The exhausted HZO@GAE could be fully regenerated by alkali treatment for repeated use without any loss in decontamination efficiency. In column assays, the HZO@GAE column successively produced ~2400 bed volume (BV) clean water ([As]<10 µg/L) from synthetic groundwater, exceeding twice the amount produced by the HZO@MAE column. This study may shed new light on developing highly efficient nanocomposites for water decontamination.

Unveiling the transformation of dissolved organic matter during ozonation of municipal secondary effluent based on FT-ICR-MS and spectral analysis.

Ozonation is a well-recognized process in advanced treatment of municipal secondary effluent for water reclamation. However, the transformation of dissolved effluent organic matter (dEfOM) during ozonation of real effluents, particularly at molecular level, has been scarcely reported. In this study, we performed ozonation treatments on real secondary effluents from two municipal wastewater treatment plants, and used Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and various spectroscopic techniques to probe the transformation of dEfOM at four ozone dosage levels (0.28, 0.61, 0.89, and 1.21 mg O3/mg DOC). Most of the precursors were unsaturated and reduced compounds (positive double bond equivalent minus oxygen per carbon ((DBE-O)/C) and negative nominal oxidation state of carbon (NOSC)), whereas the products were mainly the saturated and oxidized ones (negative (DBE-O)/C and positive NOSC). As the ozone dosage increased, the relative abundance of O8-19 species gradually increased in the ozonated samples, whereas an opposite trend was observed for O5-7S1 species. Further, we employed 18 types of reactions to represent the ozonation process, and found that the oxygenation reaction (+3O) possessed the largest number of possible precursor-product pairs, and CHON compounds possessed the highest reactivity. Besides the dominant oxygenation reactions, decyclopropyl (-C3H4) was relatively common reaction for CHON compounds, while it was oxidative desulfonation (-SH2) for CHOS ones. In addition, the transformation of precursors to products accompanied with the drop of (DBE-O)/C, and the increase of NOSC and the O/C ratio. The precursors with aromaticity and fluorescence were mainly correlated with the compounds featuring higher (DBE-O)/C and lower NOSC values. This study is believed to help better understand and improve the application of ozonation process in advanced treatment of real wastewater.

Enhanced Arsenite Removal from Silicate-containing Water by Using Redox Polymer-based Fe(III) Oxides Nanocomposite.

The efficient removal of arsenite [As(III)] from groundwater remains a great challenge. Nanoscale oxides of Fe(III), Zr(IV), and Al(III) can selectively remove arsenic from groundwater through inner-sphere complexation. However, owing to polysilicate coatings formation on nanoparticles surface, the ubiquitous silicate exerts remarkably adverse effects on As(III) removal. Herein, we propose a new strategy to enhance silicate resistance of nanoscale oxides by embedding them inside the redox polymer host. As a proof-of-concept, the nanocomposite HFO@PS-Cl was employed to remove As(III) from silicate-containing water. The polymer host (PS-Cl) contains active chlorine to oxidize As(III) into arsenate [As(V)], and the embedded Fe(III) oxides enabling specific adsorption toward arsenic. Silicate exerts negligible effects on As(III) removal by HFO@PS-Cl in pH 3-7, but increasing the residual arsenic concentration from 49 µg/L to 166 µg/L for the solutions treated by HFO@PS-N, i.e., the nanoscale Fe(III) oxides embedded inside the polymer host without active chlorine. During the six cyclic decontamination-regeneration assays, HFO@PS-Cl steadily reduces As(III) below 10 µg/L. As for HFO@PS-N, however, the residual arsenic increases to ~57 µg/L in the sixth run. In column mode, HFO@PS-Cl column generates >3200-bed volume (BV) clean water ([As]<10 µg/L) from the simulated As(III)-contaminated groundwater. In contrast, the values for As(V)-contaminated water and HFO@PS-N column are only ~650 BV and ~608 BV, respectively. The stoichiometric assays, XPS, and in-situ ATR-FTIR analysis demonstrate that silicate polymerization is intensively suppressed by the protons produced during As(III) oxidation, thus rendering HFO@PS-Cl with excellent silicate resistant properties.

Multifunctional STING-Activating Mn3 O4 @Au-dsDNA/DOX Nanoparticle for Antitumor Immunotherapy.

The promise of immunotherapy for cancer therapy has not been fully fulfilled because portions of tumors are immunosuppressive. To tackle this challenge, the initiation of immune system by stimulator of interferon genes (STING) pathway is explored and multifunctional STING-activating nanoparticles are rationally designed for synergistic antitumor therapy. The STING-activating nanoparticles have a formulation of Mn3 O4 @Au-dsDNA/DOX, where dsDNA is used to activate STING for immunotherapy and doxorubicin (DOX) is chosen as a model drug for chemotherapy. The STING-mediated immunity is activated, inducing interferon-ß (IFN-ß) production, increasing T cell priming, and enhancing effector T cell infiltration. Combined with chemotherapy, STING-mediated immunotherapy shows good antitumor efficacy by inhibiting tumor growth and prolonging survival rate in vivo. The promise of cancer immunotherapy can be fulfilled by combining novel antitumor immunity with innovative nanotechnology, and chemotherapy and targeted therapies.

Enhanced Nitrobenzene reduction by zero valent iron pretreated with H2O2/HCl.

In this study a novel iron-based reducing agent of highly effective reduction toward nitrobenzene (NB) was obtained by pretreating zero valent iron (ZVI) with H2O2/HCl. During the H2O2/HCl pretreatment, ZVI undergoes an intensive corrosion process with formation of various reducing corrosion products (e.g., Fe2+, ferrous oxides/hydroxides, Fe3O4), yielding a synergetic system (prtZVI) including liquid, suspensions and solid phase. The pretreatment process remarkably enhances the reductive performance of ZVI, where a rapid reduction of NB (200 mg L-1) in the prtZVI suspension was accomplished in a broad pH range (3-9) and at low dosage. Nitrosobenzene and phenylhydroxylamine are identified as the intermediates for NB reduction with the end-product of aniline. Compared with the virgin ZVI as well as another nanosized ZVI, the prtZVI system exhibits much higher electron efficiency for NB reduction as well as higher utilization ratio of Fe0. A rapid reduction of various nitroaromatics in an actual pharmaceutical wastewater further demonstrated the feasibility of the prtZVI system in real wastewater treatment.

Microbial community structures and functions of wastewater treatment systems in plateau and cold regions.

Wastewater treatment plants (WWTPs) in plateau regions have unique microbial community structures. In this study, Illumina high-throughput sequencing technology was applied to investigate microbial communities of plateau WWTPs. The research showed that microbial diversities and richness were negatively associated with the altitude and positively to the water temperature to a certain extent. The dominant phyla of plateau and control WWTPs were similar, which mainly included Proteobacteria, Bacteroidetes, Chloroflexi and Firmicutes. In plateau WWTPs, the LEfSe analysis found 4 biomarkers which can catabolize aromatic compounds, indicating the microorganisms that can degrade refractory organics might survive better in plateau WWTPs. The analysis of functional genera and enzymes showed that there was no significant difference in abundances of organic degrading bacteria, but the nitrogen removal bacteria were less abundant and phosphorus removal bacteria were more abundant in plateau WWTPs.