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Electrochemical nitrate reduction reaction (NITRR) is a promising approach to removing nitrogen pollutants in wastewater. Herein, Pd-Cu2O/CF was synthesized using a two-step method: in situ growth of cubic Cu2O nanoparticles on Cu foam (CF) and electrodeposited palladium (Pd) metal. The cubic Cu2O nanoparticles provide abundant hydrogen/oxygen-adsorbing sites, and Pd sites with outstanding hydrogen adsorption–desorption features generate more active hydrogen (H*), both of which effectively improve the activity for NITRR. It was demonstrated that Pd-Cu2O/CF had excellent performance with nitrate removal of 99.7% within 60 min. To remove total nitrogen (TN) from wastewater, NH4+ was completely oxidized to N2 within 120 min by adding Cl−, and the TN removal was up to 99.9%. Moreover, Pd-Cu2O/CF displayed long-term stability after ten cycle tests. [ABSTRACT FROM AUTHOR]

In situ combustion of heavy oil is currently the most suitable thermal method that meets energy consumption and carbon dioxide emission requirements for heavy oil recovery. The combustion catalyst needs to perform multiple roles for application; it should be capable of catalyzing heavy oil combustion at high temperatures, as well as be able to migrate in the geological formation for injection. In this work, a hyperbranched polymer composite nanometal fluid was used as the injection vector for a heavy oil in situ combustion catalyst, which enabled the catalyst to rapidly migrate to the surface of the oil phase in porous media and promoted heavy oil cracking deposition at high temperatures. Platinum (Pt) nanoparticles encapsulated with cetyl-hyperbranched poly(amide-amine) (CPAMAM), with high interfacial activity, were synthesized by a facile phase-transfer method; the resulting material is called Pt@CPAMAM. Pt@CPAMAM has good dispersion, and as an aqueous solution, it can reduce the interfacial tension between heavy oil and water. As a catalyst, it can improve the conversion rate during the pyrolysis of heavy oil in a nitrogen atmosphere. The catalyst structure designed in this study is closer to that exhibited in practical geological formation applications, making it a potential method for preparing catalysts for use in heavy oil in situ combustion to resolve the problem of catalyst migration in the geological formation. [ABSTRACT FROM AUTHOR]

The drawbacks, high energy consumption, rigorous preparation condition and high impurity contents, have been well-recognized in the preparation of widely-used polyaluminum chloride via conventional methods in industrial scale. In order to overcome the drawbacks, the fresh aluminum hydroxide gels were proposed to prepare the polyaluminum chloride (PAC G ) in this study. The optimal preparation condition of PAC G was obtained by optimizing the preparation conditions including temperature, time and acid concentration. The contents of the small/middle polymeric aluminum (Al b ) in an optimized PAC G could reach 80%. During preparation, high temperature significantly reduced the preparation time but led to a poor stability. Lower rate constants of reaction between hydroxyl-Al and Ferron, k b 1 and k b 2 , were almost equal at high basicity value. It implied that the middle polymeric aluminum (Al b 2 ) was dominant in Al b . Besides, the pseudo-first-order kinetics equation was rearranged. Coagulation by PAC G2.0 was found to be the most effective for low-turbidity water treatment but limited to a narrowest optimum range of dosage compared with other PAC G . The residual aluminum concentration of the water after coagulation by the PAC G2.5 with fresh aluminum hydroxide gels was always low even overdosing. Charge neutralization was not the predominant coagulation mechanism in this treatment. [ABSTRACT FROM AUTHOR]

PO43- and SiO32- are often used as modifier to improve stability and aggregating ability of the iron-base coagulants, however, there are few reports about their detailed comparison between the coagulation performance and mechanisms. In this study, three coagulants—polyferric phosphoric sulfate (PFPS), polysilicon ferric sulfate (PFSS), and polyferric sulfate (PFS) were synthesized; their structure and morphology were characterized by Fourier transformed infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and Scanning electron microscope (SEM). Alkali titration and Ferron species analysis were employed to investigate the hydrolysis performance and species distribution. Jar test was conducted to measure their coagulation behaviors at different dosage, pH, and temperatures in which the flocs properties were measured. The results showed that a number of new compounds were formed due to the presence of PO43- and SiO32-. Moreover, PFPS and PFSS had similar level in Fea as well as Feb. Among them, PFPS produced more multi-core iron atoms polymer and content of Feb, and the formed flocs were larger and denser. It exhibited superior coagulation performance in terms of turbidity reduction, UV254 removal and residual ferric concentration. Jar test and floc breakage/regrowth experiments indicated other than charge neutrality, the dominated mechanism involved in PFSS was the adsorption between polysilicic acid and solution particle, while PFPS was sweeping, entrapment/adsorption resulting from larger polymer colloid of Fe-P chemistry bond. [ABSTRACT FROM AUTHOR]

A series of hyperbranched polyethyleneimine (h-PEI) functioned with terminal amine groups is synthesized to remove oil from O/W emulsion. The demulsifier dehydration rate of h-PEI is systematically evaluated with the subsidiary facilities of DLS analysis, digital tensiometer and UV–vis spectrophotometer. The results indicate that h-PEI demulsifier displays satisfactory demulsification (the oil removal rate＞90%) with small dosage (＜80 mg L−1) and short settling time (＜30 min). The relatively short equilibrium time and great demulsification are ascribed to the amine groups and the molecular weight. On one hand, the hyperbranched macromolecules with amine groups can rapidly diffuse and adsorb to the oil-water interface, on the other hand, the molecules with adequate molecular weight are apt to flocculate, coalesce oil droplets, and then obtain high-efficient demulsification. The exceptional demulsification performance of h-PEI exhibits a potential role application in industrial water treatment or the petroleum demulsification industry. • A convenient synthetic process for h-PEI is developed. • Hyperbranched polymer h-PEI is an effective demulsifier for O/W emulsions of microdroplets with 90% of oil removal rate. • The combination of DLS observation and UV–vis analysis provides a new evidence to explore the demulsification mechanism. [ABSTRACT FROM AUTHOR]

The effects of the cationic surfactant (cationic cetyl trimethyl ammonium bromide, CTAB) on the improvement of the sludge dewaterability using the cationic flocculant (cationic polyacrylamide, CPAM) were analyzed. Residual turbidity of supernatant, dry solid (DS) content, extracellular polymeric substances (EPS), specific resistance to filtration (SRF), zeta potential, floc size, and settling rate were investigated, respectively. The result showed that the CTAB positively affected the sludge conditioning and dewatering. Compared to not using surfactant, the DS and the settling rate increased by 8%–21.2% and 9.2%–15.1%, respectively, at 40 mg·L−1 CPAM, 10×10−3 mg·L−1 CTAB, and pH 3. The residual turbidities of the supernatant and SRF were reduced by 14.6%–31.1% and 6.9%–7.8% compared with turbidities and SRF without surfactant. Furthermore, the release of sludge EPS, the increases in size of the sludge flocs, and the sludge settling rate were found to be the main reasons for the CTAB improvement of sludge dewatering performance. [ABSTRACT FROM AUTHOR]

The use of an electrocatalytic surface coating is important in environmental remediation using electrochemistry. In this work, a novel Ti/calcined graphene (CG)/PbO 2 sandwich electrode was successfully fabricated by a simple electrodeposition strategy for the efficient electrocatalytic oxidation of dye wastewater. The Ti/CG/PbO 2 electrode coating was uniform and the structure was compact. As the electrocatalyst was rich in graphene, the novel electrode possessed higher oxygen evolution potential, lower charge transfer resistance, stronger stability, longer service life and higher instantaneous current efficiency (ICE) compared with traditional Ti/PbO 2 electrode, thus exhibited better electrocatalytic oxidation activity and mineralization capacity. At a current density of 50 mA/cm2, up to 30 mg/L of methylene blue (MB) was almost completely oxidized in 1 h, while the MB removal efficiency at the Ti/PbO 2 electrode only reached 78.2 ± 0.01%. Various influencing factors were designed to simulate the changes of the wastewater system, importantly and interestingly, the electrode still owned the advantages of high-efficiency electrocatalytic oxidation in the complex changes of a wastewater system like pH range of 3–11 and various electrolyte concentrations. The as-prepared electrode could still maintain good degradation efficiency after 30 cycles. It was worth mentioning that the COD value was reduced to about 0 when using this electrode to deal with the actual printing and dyeing wastewater. The results showed that the Ti/CG/PbO 2 electrode was promising in the degradation of pollutants. Unlabelled Image • A novel sandwich electrode with a 0.231 mm coating and graphene intermediate layer • Successfully fabricated by electrochemical deposition • Maintained excellent electrocatalytic oxidation efficiency • Coped with changes in the water body well • Proposed the degradation mechanism and mechanism analysis of the degradation process [ABSTRACT FROM AUTHOR]