Electrically supported mediator Co(II)-activated peroxydisulfate synergistic process for organic contaminants elimination.

Among homogeneous catalysts, cobalt ions exhibit ultra-high persulfate activation performance. In this work, an electrically supported medium Co(II) activated peroxydisulfate synergistic process was established to eliminate organic contaminants in water. The synergistic catalytic effect was verified by comparing the oxidative degradation performance and reaction rate constant of different coupling systems. The decolorization ability of E-Co(II)-PDS on reactive black 5 (RB5) was explored, and the results showed that the removal rate of RB5 can reach 93.21% under the optimized conditions of current density of 5.71 mA/cm2, initial pH of 4, Co(II) concentration of 0.2 mM and PDS concentration of 5 mM. The effect of water matrix on the removal of RB5 was studied, and it was found that HCO3- and humic acid significantly inhibited the degradation of RB5, while Cl- and H2PO4- could effectively promote it at a certain concentration. Notably, the degradation of RB5 in E-Co(II)-PDS system achieved lower energy consumption, with an energy consumption per unit volume (EE/O) value of 0.4304 kWh·m-3. EPR test, quenching experiments and contribution rate analysis showed that the oxidation active species in E-Co(II)-PDS process were Co(III), sulfate radicals and hydroxyl radicals, and their oxidation contribution rates were 15.72%, 12.69% and 53.25%, respectively. Finally, the decomposition process of RB5 was proposed by the mass spectrometry results. The electric current promotes cobalt ion cycling and PDS activation through electron transfer, and induces Co(II) to promote the activation of PDS, which is the main mechanism of E-Co(II)-PDS system to achieve the robust degradation ability of RB5.

Insight into electrochemically boosted trace Co(II)-PMS catalytic process: Sustainable Co(IV)/Co(III)/Co(II) cycling and side reaction blocking.

A novel homogeneous electrocatalytic system was constructed by current-assisted trace Co(II) activating PMS (ECP) to remove reactive blue 19 (RB19). More than 93 % of RB19 was rapidly removed with only a trace dose, and the PMS was 98.35 % utilized during the reaction. By exploring the active species and analyzing the PMS consumption, it was found that current strongly accelerated the Co(III)/Co(II) redox cycle by providing electrons to Co(III), and inhibited the side reaction thus improving the PMS utilization. Electric energy per order was very low, only 0.26 kWh·m3. Radicals (SO4•-) and non-radicals (Co(III), Co(IV) and 1O2) participated in ECP system, in which SO4•- was dominant. By excluding the other three precursors (PMS, •OH and O2•-), the side reaction product SO5•- was identified as the source of 1O2 in ECP system. Combining chelating agent EDTA and chemical probe PMSO, Co(IV) was considered formed by single and double charge transfer. Five degradation pathways of RB19 were proposed using mass spectrometry and DFT calculation. The ecotoxicity and mutagenicity of RB19 and its transformation products were predicted using software simulation. These studies provided an interesting insights into the synergistic Co(II)-PMS systems and offered a new strategy for electrochemical processes.

Catalytic hydrothermal liquefaction of lignin for production of aromatic hydrocarbon over metal supported mesoporous catalyst.

Catalytic hydrothermal liquefaction (HTL) of lignin was examined at various temperature (250-310 °C) and reaction time in the presence of different solvents (water, methanol and ethanol) with different metal supported on MCM-41 mesoporous catalyst. In case of ethanol solvent, the maximum bio-oil yield of 56.2 wt% was obtained with Ni-Al/MCM-41. However in case of water, bio-oil yield was (44.3 wt%); while significantly improves bio-oil yield for methanol solvent (48.1 wt%). It is indicated that alcoholic solvents promoted the lignin decomposition, while in the presence of catalyst; water solvent significantly improves lignin degradation. Loading of Ni and Al on MCM-41, the acid strength of the catalyst increased, which enhanced lignin degradation. From the GC-MS analysis, the main G-type (ca.54%) phenolic compounds were produced with higher percentage of aromatic hydrocarbon compounds. CHNS and GPC analysis showed that catalytic liquefaction encouraged hydrodeoxygenation, which produced lower oxygen content bio-oil with lower molecular weight.

A microblock structure type of anionic flocculant for hematite wastewater treatment: template copolymerization mechanism and enhanced flocculation effect.

In this study, a novel anionic template polymer (TPAS) with microblock structure was prepared by ultraviolet light (UV)-assisted template copolymerization (UV-TP). Acrylamide (AM) and sodium styrene sulfonate (SSS) were selected as monomers and polypropylene ammonium chloride (PAAC) was chosen as the template. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), nuclear magnetic resonance hydrogen spectroscopy (1H NMR), and thermogravimetry/differential scanning calorimetry (TG/DSC) were used to characterize the polymer chemical structure. The results showed that the attractive anionic microblock structure was formed in TPAS. Besides, the association constant (KM) and template reaction kinetics analysis results indicated that the polymerization reaction followed I (ZIP) template copolymerization mechanism. It proved the microblock structure formation again. The anionic microblock structure in TPAM could greatly improve the ability of charge neutralization, electrical patching, and bridging. After the hematite wastewater was conditioned by TPAS with this novel anionic microblock structure, the generated hematite flocs had larger particle size and denser structure. It was favorable for the reduction of turbidity, and the turbidity removal rate could reach 97.8%. TPAS showed excellent flocculation performance for hematite wastewater and had a broad market application prospect.