Occurrence and risks of pharmaceuticals, personal care products, and endocrine-disrupting compounds in Chinese surface waters.

The continuous and rapid increase of chemical pollution in surface waters has become a pressing and widely recognized global concern. As emerging contaminants (ECs) in surface waters, pharmaceutical and personal care products (PPCPs), and endocrine-disrupting compounds (EDCs) have attracted considerable attention due to their wide occurrence and potential threat to human health. Therefore, a comprehensive understanding of the occurrence and risks of ECs in Chinese surface waters is urgently required. This study summarizes and assesses the environmental occurrence concentrations and ecological risks of 42 pharmaceuticals, 15 personal care products (PCPs), and 20 EDCs frequently detected in Chinese surface waters. The ECs were primarily detected in China's densely populated and highly industrialized regions. Most detected PPCPs and EDCs had concentrations between ng/L to µg/L, whereas norfloxacin, caffeine, and erythromycin had relatively high contamination levels, even exceeding 2000 ng/L. Risk evaluation based on the risk quotient method revealed that 34 PPCPs and EDCs in Chinese surface waters did not pose a significant risk, whereas 4-nonylphenol, 4-tert-octylphenol, 17α-ethinyl estradiol, 17ß-estradiol, and triclocarban did. This review provides a comprehensive summary of the occurrence and associated hazards of typical PPCPs and EDCs in Chinese surface waters over the past decade, and will aid in the regulation and control of these ECs in Chinese surface waters.

Improved desalination performance of flow-electrode capacitive deionisation by a novel drop-shape channel.

As an emerging desalination technology, flow-electrode capacitive deionisation (FCDI) has the advantages of theoretically infinite adsorption capacity and applicability to high-concentration brine. However, during the operation of FCDI, the flow electrode in the S-shape channel is prone to sedimentation and clogging the channel. This undesirable phenomenon brings low efficiency and security issues. Therefore, a drop-shape channel was designed for FCDI to improve the flow regime of the flow electrode. The flow simulation of the drop-shape channel was performed to select the appropriate geometry to avoid the formation of the vortex and low-velocity region. The simulation results showed that the streamlined design of the drop-shape channel has insignificant velocity gradients. It significantly reduces the low-velocity region and improves the phenomenon of particle sedimentation. The desalination performance with varieties of electrode flow rate, AC content, and voltage was used to investigate the advantage between S-shape and drop-shape channels. It was found that under the conditions of low flow rate, high AC content, and high voltage, the drop-shape channel FCDI system could still obtain better ASRR and CE.

A preliminary attempt at capacitive deionization with PVA/PSS gel coating as an alternative to ion exchange membrane.

PVA/PSS composite gel membrane electrode for membrane capacitive deionization (MCDI) was fabricated and characterised in the present study. The composite electrode with ion exchange surface is prepared by coating glutaraldehyde cross-linked polyvinyl alcohol (PVA) composite hydrogel, with Poly (Sodium 4-Styrenesulfonate) (PSS) added into the network, on the surface of activated carbon (AC) electrode. The feasibility of the gel membrane is analyzed by rheological, swelling rates and ion exchange capacity tests. Then electrochemical test and desalination test are used to study the performance of the MCDI electrode. The results show that coating of composite hydrogel layer improved the hydrophilicity, specific capacitance and lower interfacial electron transfer resistance of the electrode. Finally, we assemble the asymmetrical CDI cell with PVA/PSS composite gel electrode and AC electrode. Compared with the AC electrode, the salt adsorption capacity of PVA6-PSS15 can reach 18.9 mg g-1 and stable charge efficiency at 73.0% at operating voltage of 1.2 V. The decrease in specific capacitance of PVA6-PSS15 after 50 cycles is 1.33%, indicating that the electrode has a good cycling life. The gel membrane coated electrode prepared by PSS provides a new idea for the development of MCDI.

Effects of biochar-based materials on nickel adsorption and bioavailability in soil.

The potential for toxic elements to contaminate soil has been extensively studied. Therefore, the development of cost-effective methods and materials to prevent toxic element residues in the soil from entering the food chain is of great significance. Industrial and agricultural wastes such as wood vinegar (WV), sodium humate (NaHA) and biochar (BC) were used as raw materials in this study. HA was obtained by acidizing NaHA with WV and then loaded onto BC, which successfully prepared a highly efficient modification agent for nickel-contaminated soil, namely biochar-humic acid material (BC-HA). The characteristics and parameters of BC-HA were obtained by FTIR, SEM, EDS, BET and XPS. The chemisorption of Ni(II) ions by BC-HA conforms to the quasi-second-order kinetic model. Ni(II) ions are distributed on the heterogeneous surface of BC-HA by multimolecular layer adsorption, which accords with the Freundlich isotherm model. WV promotes better binding of HA and BC by introducing more active sites, thus increasing the adsorption capacity of Ni(II) ions on BC-HA. Ni(II) ions in soil are anchored to BC-HA by physical and chemical adsorption, electrostatic interaction, ion exchange and synergy.

Effect of anion-exchange membrane type for FCDI performance at different concentrations.

Brackish water was an important alternative source of freshwater. Desalination using flow electrode capacitive deionization (FCDI) needs to explore the role of ion exchange membranes (IEM) of FCDI. In this study, brackish water was desalinated using FCDI, and anion exchange membranes with different characteristics were used in the FCDI cell to investigate their influence. The result showed that the membrane polymer matrix was the main influencing factor for ion transport. Ion exchange capacity (IEC) has a huge impact that low IEC made the various ion transport priority. Low IEC not only limits ion transport but also leads to ion leakage in seawater. Resistance had a significant blockage to the effect with weak intensity.

Low-nitrite generation Cu-Co/Ti cathode materials for electrochemical nitrate reduction.

In order to reduce by-product nitrite, a more toxic compound than nitrate, and increase high value-added products ammonia in the electrochemical reduction nitrate process, the novel Cu-Co/Ti cathode material was applied in this process. In this paper, the electrochemical process was carried out in a single compartment electrolytic cell, and with Cu-Co/Ti electrode as cathode, identifying the effects of current density, pH, electrolytes in the nitrate reduction, and the distribution of products. The Cu-Co/Ti cathode exhibited 94.65% NO3--N (nitrate-N) removal, 0.18% NO2--N (nitrite-N) generation, and 40.86% NH4--N (ammonia-N) generation with the assistance of Na2SO4 electrolyte in 6 h at 10 mA cm-2 and pH 6. Compared with the Cu/Ti cathode, the higher nitrate removal ratio and lower nitrite generation ratio were obtained on the Cu-Co/Ti cathode. The excellent performance of Cu-Co/Ti cathode is ascribed to the synergy of Cu and Co, which couples the facilitation of nitrate conversion to nitrite and the acceleration of nitrite reduction on the Cu-Co/Ti cathode. The LSV curves showed that nitrate and nitrite might undergo indirect and direct reduction reactions on Cu-Co/Ti cathode. The possible pathways of nitrate reduction on the Cu-Co/Ti cathodes were proposed. These results highlight the viability of using the Cu-Co/Ti cathode developed at this work for the nitrate removal from contaminated waters. This study achieved low-nitrite generation by Cu-Co/Ti cathode during electrochemical nitrate reduction.

Electrochemical degradation of chloramphenicol using Ti-based SnO2-Sb-Ni electrode.

Antibiotic residues may be very harmful in aquatic environments, because of limited treatment efficiency of traditional treatment methods. An electrochemical system with a Ti-based SnO2-Sb-Ni anode was developed to degrade a typical antibiotic chloramphenicol (CAP) in water. The electrode was prepared using a sol-gel method. The performance of electrode materials, impact factors and dynamic characteristics were evaluated. The Ti-based SnO2-Sb-Ni electrode was compact and uniform as shown by characterization using SEM and XRD. The electrocatalytic oxidation of CAP was carried out in a single-chamber reactor by using a Ti-based SnO2-Sb-Ni electrode. For 100 mg L-1 CAP, the CAP removal ratio of 100% and the TOC removal ratio of 60% were obtained at the current density of 20 mA cm-2 and in a neutral electrolyte at 300 min. Kinetic investigation has shown that the electro-oxidation of CAP on a Ti-based SnO2-Sb-Ni electrode displayed a pseudo-first-order kinetic model. Free radical quenching experiments presented that the oxidation of CAP on Ti-based SnO2-Sb-Ni electrode resulted from the synergistic effect of direct oxidation and indirect oxidation (·OH and ·SO4-). Doping Ni on the Ti/SnO2-Sb electrode for CAP degradation was presented in this paper, showing its great application potential in the area of antibiotic and halogenated organic pollutant degradation.

Immobilization properties and adsorption mechanism of nickel(II) in soil by biochar combined with humic acid-wood vinegar.

Biochar (BC) combined with humic acid (HA) and wood vinegar (WV) was designed and prepared as an inexpensive, effective, and environmentally friendly immobilization material (BHW) for metal-polluted soil. The influences of the wood vinegar and humic acid on the immobilization properties and adsorption mechanism of this new material were also investigated. The remediation performance was evaluated using a laboratory-made, nickel-contaminated soil with a Ni2+ concentration of 200 mg per kg surface soil (top 20 cm from agricultural land). The results indicated that the immobilization ratio sequence of nickel (II) in the soil was BC< BH< BHW. The maximum adsorption capacity increased in the same order: BC< BH< BHW. All three adsorption isotherms were better fitted by the Freundlich model, which were consistent with the surface heterogeneity of the remediation materials. The cause of this surface heterogeneous migration may be due to the increase in oxygen-containing groups in the BC introduced by the HA and WV. The WV can increase the number of the oxygen-containing groups in the BC combined with HA, which enhanced the adsorption and immobilization of Ni2+ ions. The results suggested that BHW is recommended for the remediation of metal-contaminated soils, because of its high efficacy, economic feasibility, environmental and food safety.

Wood vinegar enhances humic acid-based remediation material to solidify Pb(II) for metal-contaminated soil.

Heavy metal lead is a typical widespread potentially toxic element (PET) contamination due to their extensive and wide applications in industrial processes. The development of cost-effective methods for preventing potentially toxic element lead residues from soil into food is thus highly desirable. A new type of humic acid-based remediation material (HA/WV) incorporating humic acid salt (HA), biochar powder (BC), and wood vinegar (WV), which is a cheap and environmentally friendly industrial by-product from charcoal processing, was prepared and evaluated. The results showed that 0.10 g remediation material HA/WV with a mass ratio of 1:1 was added to 1 kg surface soil of 0-20 cm from agricultural land contaminated by 300 mg Pb2+, the reduction ratio of available Pb in soil can reach 61.4%. Especially, wood vinegar can enhance the reduction ratio of available Pb by at least 14.7% over without wood vinegar. Furthermore, according to the analysis of adsorption interaction and the electrostatic attraction between Pb(II) and oxygen-containing functional groups on HA/WV are the dominant mechanisms responsible for Pb(II) sorption. The wood vinegar liquid can improve the oxygen-containing group in HA/WV, which can enhance the complexation of remediation materials and Pb(II) ion.

Preparation of a novel Cu-Sn-Bi cathode and performance on nitrate electroreduction.

Cu-Sn-Bi layer coated on Ti substrate was prepared using electrodeposition method and applied as cathode material for electrochemical reduction of nitrate in this research. Linear sweep voltammetry (LSV), chronoamperometry (CA), scanning electron microscope (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) were used to scrutinize the electrochemical performance and the cathode materials. LSV results illustrated that Cu-Sn-Bi cathode possessed the ability for nitrate reduction. Preparation conditions including deposition time, current density, temperature and the content of Bi were optimized based on NO3 -N removal and byproducts selectivity. Results showed that the cathode with Bi content of 3.18 at.%, and electrodepositing at current density of 6 mA cm-2, 35 °C for 30 min achieved the best performance during the experiment. The increase of Bi content could improve the electrocatalytic activity and stability of the cathode. Compared with other common researched cathodes (Cu and Fe), Cu-Sn-Bi (3.18 at.%) exhibited better performance, i.e. the highest NO3 -N removal of 88.43% and the selectivity of harmless N2 was 77.80%. The kinetic studies showed that the reduction of nitrate on Cu-Sn-Bi followed pseudo-first-order kinetics.

[Removal of 2,4-dichlorophenol in Underground Water by Stabilized Nano Zero-valent Iron].

To restrain the nano zero-valent iron (NZVI) in aqueous solution from being reunited and oxidized, this paper used sodium carboxymethyl starch (CMS), which is an environmentally friendly and cheap material, for coating and surface modification of NZVI so as to improve its dispersity and suspension property. Transmission Electron Microscope (TEM) and X-ray diffraction (XRD) were used to study the microstructure and components of the modified NZVI, and the 2,4-dichlorophenol 2,4-(DCP) removal efficiency was researched through chemical experiment. Experiments showed that the modified NZVI was about 80~100 nm in diameter, present as chain or dispersed particles. The main component was zero-valent iron, and it had strong reducibility. When the proportion of CMS was 80.00%, the suspension property was the best; The NZVI after CMS coating and surface modification retained the original activity. In the experiment investigating the removal effect of 2,4-DCP using different proportion of cladding, the same finding was obtained. When the CMS's proportion was 80%, the removal effect was the best, reaching up to 83.69%, and the dechlorination and degradation were apparent.

Permeable reactive barrier of coarse sand-supported zero valent iron for the removal of 2,4-dichlorophenol in groundwater.

In this study, coarse sand-supported zero valent iron (ZVI) composite was synthesized by adding sodium alginate to immobilize. Composite was detected by scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray fluorescence (XRF). SEM results showed that composite had core-shell structure and a wide porous distribution pattern. The synthesized composite was used for degradation of 2,4-dichlorophenol (2,4-DCP) contamination in groundwater. Experimental results demonstrated that degradation mechanism of 2,4-DCP using coarse sand-supported ZVI included adsorption, desorption, and dechlorination. 2,4-DCP adsorption was described as pseudo-second-order kinetic model. It was concluded that dechlorination was the key reaction pathway, ZVI and hydrogen are prime reductants in dechlorination of 2,4-DCP using ZVI.