Preparation of amphiphilic cationic polyacrylamide (CPAM) with cationic microblock structure to enhance printing and dyeing sludge dewatering and condition performance.

Flocculation is an important pretreatment technology for sludge dewatering, and the flocculant's performance is the key factor to determine the flocculation effect. Cationic polyacrylamide (CPAM) is commonly used in dewatering and conditioning of printing and dyeing sludge (PD sludge), and the research of high-efficiency flocculant is a hot spot in the field of PD sludge dewatering. Hydrophobic butylacrylate (BA) and (2-(Methacryloyloxy)ethyl) trimethylammonium chloride (DMC) were introduced into the copolymer, and amphiphilic (hydrophilic/lipophilic) CPAM, namely TP-ADB, with microblock structure was synthesized by ultrasonic initiated template copolymerization in this study. The functional group composition of TP-ADB was determined by FTIR and 1H NMR. Thermogravimetric analysis (TGA) showed that TP-ADB had good thermal stability. The amphiphilic rheological properties of the copolymer were measured according to the apparent viscosity. In addition, 1H NMR and TGA results confirmed the existence of microblock structure in the copolymer chain. The polymerization mechanism was discussed by association coefficient (KM) measurement. The results showed that the template copolymerization initiated by ultrasonic followed the law of free radical copolymerization. The pre-adsorption of DMC with sodium polyacrylate template (NaPAA) before the reaction confirmed that the template polymerization accorded with ZIP I mechanism. The cationic microblock structure and hydrophobic association of TP-ADB promoted the dewatering performance of PD sludge (FCMC = 72.9%, turbidity removal rate = 98.9%, SRF = 4.2 × 1012 m·kg-1). Hydrophobic association enhanced the bridging, sweeping, and net catching effect, and promoted the growth of floc size and fractal dimension. Cationic microblock structure can produce compact floc with higher mechanical strength by enhancing electrical neutralization and electrical patching. As a skeleton, the compressibility of filter cake was reduced and the permeability was enhanced, and the PD sludge dewatering effect was significantly improved.

Efficient removal of RR2 dye by electro- Ce(III) process with its elegant arts and attractive charm in performance, energy consumption and mechanism.

Reactive red 2 (RR2) azo dye wastewater poses a serious hazard to the water environment health, so using a novel and efficient Electro- Ce(III) (E- Ce(III)) process takes on a critical significance in treating RR2 dye wastewater. In this study, the effects of a variety of single-factor conditions on RR2 removal efficiency were evaluated in depth. The results indicated that the optimal experimental conditions are as reaction temperature of 25 °C, Na2SO4 concentration of 25 mM, Ce(III) concentration of 0.3 mM, pH of 4.0, and current density of 40.0 mA/cm2. When the RR2 dye wastewater was treated for 40 min under the optimal experimental conditions, a high removal rate of 99.8% for RR2 was obtained. It is suggested that the background ion PO43- in the dye wastewater inhibits the E-Ce (III) process, whereas Cl- facilitates this process. Moreover, the yield of Ce(IV) increases with the increase of the current density. At the current density of 40.0 mA/cm2, a reasonable energy consumption of 3.85 kW h/gTOC for the process was obtained after the 3-h treatment. The effects of different degradation processes (including Direct Electrooxidation (DEO), single Ce(III), and E-Ce (III)) on RR2 removal efficiency and TOC change were compared. The types of oxidizing substances in the E-Ce (III) process were detected, and the mechanism of RR2 oxidative degradation in the E-Ce (III) process was summarized. The result suggests that the E-Ce (III) process has low power consumption. Meanwhile, in the E-Ce (III) process, free reactive Ce(IV) with strong oxidation is continuously generated, RR2 can be efficiently degraded. And the continuous cycle transformation between Ce(III) and Ce(IV) maintains the strong oxidation of the process. The contribution of free reactive Ce(IV) and DEO to RR2 degradation was obtained as 58.8% and 39.8%, respectively. The combined effect of Ce(IV) and DEO played a major role in the E-Ce (III) process, while ·OH exhibited a relatively weak effect (nearly 1.4%). RR2 was comprised of 13 major intermediates, and the biodegradability of wastewater was improved significantly after treatment, thus facilitating the further mineralization and biodegradation of the products. The E- Ce(III) process is novel, efficient, and environment-friendly, and has a large market application space, suggesting that it can be applied as an efficient, economic, and sustainable water treatment process.

FeS redox power motor for PDS continuous generation of active radicals on efficient degradation and removal of diclofenac: Role of ultrasonic.

Diclofenac (DCF), as a typical representative of PPCPs, has potential ecotoxicity to the water environment. In this study, ultrasound (US) enhanced ferrous sulfide (FeS)-activated persulfate (PDS) technology (US/FeS/PDS) was used to degrade DCF. By comparing the degradation effects of US, US/PDS, FeS/PDS and US/FeS/PDS systems on DCF, this study confirmed the synergy and strengthening effects of US. The influences of single-factor experimental conditions on the US/FeS/PDS system were investigated and optimized. The FeS catalysts before and after the reaction were characterized and analyzed by X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The heterogeneous reaction proceeded on the surface of FeS, and a small part of FeS2 was formed on FeS surface. During the reaction, the proportion of S2- on the catalyst surface decreased from 51% to 44%. Correspondingly, the proportion of Sx2- increased from 21% to 26%. It indicated that S2- was oxidized into Sx2- in the reaction, and the loss electrons of S2- caused the reduction of Fe3+ to Fe2+on the FeS surface, which promoted the cycle between Fe2+ and Fe3+ in turn. Furthermore, SO4- and ‧OH were the main active free radicals, of which the contribution rate of ‧OH was about 34.4%, while that of SO4- was approximately 52.2%. In US/FeS/PDS, the introduction of US could promote the dissolution of iron on the FeS surface. US contributed to the formation of a redox power motor between S2-Sx2- and Fe2+-Fe3+, which continuously decomposed PDS to generate sufficient active SO4- and ‧OH radicals, thereby efficiently and continuously degrading DCF. Finally, the related mechanism of DCF degradation by US/FeS/PDS was summarized. Overall, US/FeS/PDS can not only efficiently degrade and remove DCF, but also has potential application value in organic pollution removal and wastewater purification.

Application of Coagulation-Membrane Rotation to Improve Ultrafiltration Performance in Drinking Water Treatment.

The combination of conventional and advanced water treatment is now widely used in drinking water treatment. However, membrane fouling is still the main obstacle to extend its application. In this study, the impact of the combination of coagulation and ultrafiltration (UF) membrane rotation on both fouling control and organic removal of macro (sodium alginate, SA) and micro organic matters (tannic acid, TA) was studied comprehensively to evaluate its applicability in drinking water treatment. The results indicated that membrane rotation could generate shear stress and vortex, thus effectively reducing membrane fouling of both SA and TA solutions, especially for macro SA organics. With additional coagulation, the membrane fouling could be further reduced through the aggregation of mediate and macro organic substances into flocs and elimination by membrane retention. For example, with the membrane rotation speed of 60 r/min, the permeate flux increased by 90% and the organic removal by 35% in SA solution, with 40 mg/L coagulant dosage, with an additional 70% increase of flux and 5% increment of organic removal to 80% obtained. However, too much shear stress could intensify the potential of fiber breakage at the potting, destroying the flocs and resulting in the reduction of permeate flux and deterioration of effluent quality. Finally, the combination of coagulation and membrane rotation would lead to the shaking of the cake layer, which is beneficial for fouling mitigation and prolongation of membrane filtration lifetime. This study provides useful information on applying the combined process of conventional coagulation and the hydrodynamic shear force for drinking water treatment, which can be further explored in the future.

Fabrication of electrochemically-modified BiVO4-MoS2-Co3O4composite film for bisphenol A degradation.

A new electrochemically-modified BiVO4-MoS2-Co3O4 (represented as E-BiVO4-MoS2-Co3O4) thin film electrode was successfully synthesized for environmental application. MoS2 and Co3O4 were grown on the surface of BiVO4 to obtain BiVO4-MoS2-Co3O4. E-BiVO4-MoS2-Co3O4 film was achieved by further electrochemical treatment of BiVO4-MoS2-Co3O4. The as-prepared E-BiVO4-MoS2-Co3O4 exhibited significantly enhanced photoelectrocatalytic activity. The photocurrent density of E-BiVO4-MoS2-Co3O4 thin film is 6.6 times that of BiVO4 under visible light irradiation. The degradation efficiency of E-BiVO4-MoS2-Co3O4 for bisphenol A pollutant was 81.56% in photoelectrochemical process. The pseudo-first order reaction rate constant of E-BiVO4-MoS2-Co3O4 film is 3.22 times higher than that of BiVO4. And its reaction rate constant in photoelectrocatalytic process is 14.5 times or 2 times that in photocatalytic or electrocatalytic process, respectively. The improved performance of E-BiVO4-MoS2-Co3O4 was attributed to the synergetic effects of the reduction of interfacial charge transfer resistance, the formation of oxygen vacancies and sub-stoichiometric metal oxides and higher separation efficiency of photogenerated electron-hole pairs. E-BiVO4-MoS2-Co3O4 is a promising composite material for pollutants removal.

Mechanism and efficiency of contaminant reduction by hydrated electron in the sulfite/iodide/UV process.

Advanced reduction by the extremely strong reducing species, hydrated electron (eaq-), is a promising and viable approach to eliminate a wide variety of persistent and toxic contaminants. In this study, we proposed a sulfite/iodide/UV process, which offered efficient production of eaq- for contaminant reduction. Using monochloroacetic acid (MCAA) as a simple eaq- probe, the availability of eaq- was assessed, and the mechanism involving the roles of S(IV) and iodide in the process was elucidated. A pronounced synergistic effect of S(IV) and iodide was observed in MCAA reductive dechlorination. The efficiency was much more dependent on the iodide concentration due to its higher absorptivity and quantum yield of eaq-. S(IV) played a dual role by producing eaq- via photoionization of SO32- and by reducing the reactive iodine species formed to avoid their scavenging of eaq-. When S(IV) was available, cycling of iodide occurred, favoring the constant eaq- production. The formation and transformation kinetics of sulfite radical were studied to verify the roles of S(IV) and iodide in the process. A kinetic model of MCAA dechlorination was also developed to quantify the eaq--initiated reduction efficiency, highlighting the effects of S(IV), iodide, and pH. High pH favored the reduction, and the process was still effective in field surface water. This study underscores the importance of producing eaq- efficiently and of minimizing the eaq- scavenging of intermediates inherently formed and accumulated, and highlights the potential of the sulfite/iodide/UV process to efficiently eliminate recalcitrant contaminants.