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In this work, we proposed a new combined process to produce high-purity water which can meet the requirement in many advanced high-tech applications. Here, we mainly focus on the rejection of ions and organic matters, which is characterized by conductivity/resistivity and total organic carbon (TOC), respectively. Ground water with TOC concentration of 373 μg/L and conductivity of 755 μS/cm was fed to the combined process. The effects of granular activated carbons (GACs) (Haycard and Calgon), ultraviolet (UV) sterilizers (single-wavelength and multiwavelength) and ion-exchange (IX) resins (SMT200L, SMT100L and UP6040) on TOC removal efficiency were systematically investigated. We found that a multiwavelength UV185/254, GAC (Calgon) and IX resin (SMT100L) had a higher TOC removal efficiency. We then optimized ultrapure water system and assembled units to the system, which consisted of double-pass reverse osmosis (RO) membranes, IX resin (SMT100L), multiwavelength UV185/254 sterilizer, GAC (Calgon) + IX resin (SMT100L) and a final filter. The optimized ultrapure water system produced water with a high resistivity (18.2 MΩ·cm) and low TOC concentration (2.37 μg/L). This research provides a new available combined process for ultrapure water production design.

Nanofiltration (NF) membranes have many excellent applications (e.g., removing multivalent ions and pretreating water before reverse osmosis, RO), but their relatively high cost limits their application. Especially in recent years, researchers have paid substantial attention to reducing the cost of NF membranes. In this paper, high-performance NF membranes were fabricated using interfacial polymerization (IP) methods. The polymer concentration, IP solution concentration, and thermal treatment conditions were varied. The synthesized membranes were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), a contact angle goniometer, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance fourier transform infrared (ATR-FTIR) spectroscopy, and performance tests. The results show that water flux was significantly improved using a hot-water thermal treatment method. Our fabricated thermal-treated NF membrane had an approximately 15% higher water permeability with a value of 13.6 L/(m 2 h bar) than that of the commercially available GE HL membrane with a value of 11.8 L/(m 2 h bar). Our membranes had the same MgSO 4 rejection as that of the GE HL membrane. We found that the thermal treatment causes the NF membrane surface to be smoother and have a high crosslinking degree.

To advance commercial application of forward osmosis (FO), we investigated the effects of two additives on the performance of polysulfone (PSf) based FO membranes: one is poly(ethylene glycol) (PEG), and another is PSf grafted with PEG methyl ether methacrylate (PSf-g-PEGMA). PSf blended with PEG or PSf-g-PEGMA was used to form a substrate layer, and then polyamide was formed on a support layer by interfacial polymerization. In this study, NaCl (1 mol∙L–1) and deionized water were used as the draw solution and the feed solution, respectively. With the increase of PEG content from 0 to 15 wt-%, FO water flux declined by 23.4% to 59.3% compared to a PSf TFC FO membrane. With the increase of PSf-g-PEGMA from 0 to 15 wt-%, the membrane flux showed almost no change at first and then declined by about 52.0% and 50.4%. The PSf with 5 wt-% PSf-g-PEGMA FO membrane showed a higher pure water flux of 8.74 L∙m–2∙h–1 than the commercial HTI membranes (6–8 L∙m–2∙h–1) under the FO mode. Our study suggests that hydrophobic interface is very important for the formation of polyamide, and a small amount of PSfg-PEGMA can maintain a good condition for the formation of polyamide and reduce internal concentration polarization.

Advanced oxidation processes (AOPs) based on the bimetallic system has been demonstrated as a promising way to enhance the degradation of pollutants in the water. In this study, the degradation of Rhodamine B (RhB) in a zero-valent iron (ZVI)/ peroxymonosulfate system with Cu2+ was thoroughly investigated. RhB could be efficiently removed (99.3 %) in the optimal ZVI/PMS/Cu2+ system, while only 58.2 % of RhB could be degraded in the ZVI/PMS system. The influence of reaction parameters on the degradation of RhB was further investigated. Quenching experiments and electron paramagnetic resonance (EPR) tests revealed that various reactive oxygen species could be generated in the ternary system, of which, 1O2 and O2- were identified for the first time. The effect of various anions, NOM and different water matrix were also considered at different concentrations. A variety of byproducts and degradation pathways were identified using HPLC/MS/MS. Finally, the Quantitative Structure Activity Relationship (QSAR) method of Toxicity Estimation Software Tool (TEST) was applied to estimate the toxicity of the byproducts and the results indicated that the overall toxicity of the target was relatively reduced. This study demonstrated the potential for the removal of environmental reluctant pollutants in water via the combined radical and non-radical pathways.