Preparation and Photocatalytic Application of the Composites PMo12/AgNPs Based on Polyoxometalates

Supported catalysts, consisting of PMo12 immobilized on silver nanomaterials at different recombination time and the silver nanomaterials with different template sodium citrate amount characterized by FT-IR, XRD, SEM, UV-vis and other test methods. The results show that the AgNPs are relatively uniformed with sizes between 100–300 nm when the sodium citrate addition amount is 9.0 mL. As the reaction time of PMo12/AgNPs increases, the adhesion of AgNPs on the surface of PMo12 becomes more complete. Using PMo12 and PMo12/AgNPs composite materials as catalysts, methylene blue (MB) is photocatalytically degraded under simulated visible light conditions. The results show that PMo12 can catalyze MB effectively, and the decolorization rate reached 98.6% when the catalyst content is 2 g/L, the solution pH is 3 and the MB concentration is 5 mg/L. Under the same experimental conditions, photocatalytic performance of the PMo12/AgNPs system is better than that of the PMo12 further improved the photocatalytic degradation effect of the MB solution with a decolorization rate of 100%. The composite still keeps good photocatalytic activity and stability after three cycles of use. Finally, the catalytic mechanism of the POMs composite material is preliminarily discussed.

Preliminary Study Into the Decolorization of Selected Dyes By the Ozone Application

Synthetic dyes widely used in many kinds of industry affect the colour of wastewater when released to environment due to insufficient treatment in typical sewage treatment plants. Only a small dose of those dyes may significantly affect colour of water and, according to the chemical composition, may pose risks to wildlife and humans. In the research described in this study, decolorization of three various dyes was investigated. Since colour removal of Congo Red such as Methylene blue using ozone have been reported by several authors, and the literature on Naphthol Green B is rather limited, in the present study we compare the decolorization rate of CR, MB and NGB. The colour removal occurred quickly and more than 90% of colour reduction was achieved within 3-6 minutes throughout all tested pH of the solution.

Preparation of Ti/SnO2-Sb/Rare Earth Electrodes Containing Different Contents of Ni Intermediate Layer for Efficient Electrochemical Decolorization of Rhodamine B

Water contamination by dyes discharged from many industries is an environmental issue of great matter. Electrochemical oxidation is an advanced approach for wastewater treatment. In this study, the composite electrodes of Ti/SnO2-Sb-Ni/rare earth have been modified using rare earth elements (Re) Gd, Ce, Eu, and Er and various molar ratios of tin and nickel intermediate layer, and their electrochemical oxidation effects were scrutinized. To analyze the decolorization performance of the electrodes, Rhodamine B (RhB) dye was utilized as a target pollutant. Accelerated life testing indicated that the longer service life could be observed in Ni (3.5%)/Re and Ni (5%)/ Re electrodes compared with other modified Ni (0%, 1%, and 2%)/Re electrodes. Compared with the color removal efficiencies of the Ni (2%)/Re electrodes, the decolorization rate of 90% after treatment for 60 min and the low energy consumption of 3.621 kW h·m−3 can be achieved at the Ni (2%)/Gd electrode under the experimental condition of 100 mg·L−1 RhB. The best decolorization rate was observed at the Ni (2%)/Re electrodes among other Ni and no adding Ni-doped Re electrodes. The characterization of the electrodes was described, consisting of surface morphology, oxygen evolution potential, and a crystallographic and elemental combination of the coatings.

Selective oxidation and direct decolorization of cationic dyes by persulfate without activation

The aim of this work was to investigate the selective oxidation and direct decolorization of selected organic dyes (Methylene Blue (MB), Rhodamine B (RhB) and Orange II (OrgII)) by persulfate (PDS) without activation. Results show that the decolorization rate of MB was up to 58.0% within 10 minutes, while those of RhB and OrgII were only about 29.6% and 3.0% after 80 minutes, respectively. In comparison with the negligible impacts of pH from 2.0 to 9.0 on MB and OrgII decolorization, RhB decolorization rate obviously varied with the pH changes, and acid pH condition was beneficial for RhB decolorization. Quenching tests implied that the decolorization of dyes by PDS without activation was a nonradical oxidation processes rather than sulfate radical oxidation. A plausible mechanism is that the decolorization process is attributed to the charged states of the dyes at different pH conditions, and thus direct electron transfer from dyes to PDS may occur, which is responsible for the bleaching of dyes. This study points out the potential bleaching capability of PDS without activation on cationic dyes, which may have important implications for selective oxidation treatment of dye wastewater.

Enhancement of performance for graphite felt modified with carbon nanotubes activated by KOH as Cathode in electro-fenton systems

The electro-Fenton (EF) process is one of the advanced oxidation processes (AOPs). Graphite felt is widely used as an cathode material for the EF process, and its performance can be improved by surface modification. Active carbon nanotubes (ACNTs) have more oxygen-containing functional groups and better electrochemical properties compared to Multi-wall carbon nanotubes (MWCNTs). In this study, graphite felt was used as the substrate, and composite cathodes were prepared by surface treatment using MWCNT, graphene, and ACNTs. Rhodamine B (RhB) dye decolorization tests were then conducted to investigate the degradation performance of the EF system with different cathodes. The results showed that based on the micromorphology of ACNT, the tubular form of MWCNT was activated into a GR-like flake structure, it was also found that the strength of the oxygen-containing functional groups of ACNT improved significantly. The activated MWCNT/C cathode exhibited a 60-min decolorization rate of 77.28% compared to the unactivated MWCNT/C cathode, whereas the decolorization rate of the ACNT/C cathode increased to 85.01% after activation, which was close to that of the GR/C cathode at 88.55%. In summary, the ACNT/C cathode exhibited degradation efficiency comparable to that of the GR/C cathode.

Study on Adsorption of Dye Wastewater by Modified Fly Ash

Used fly ash as raw material, it was modified by acid, alkali and high temperature to produce modified fly ash adsorbent, sulfuric acid modified fly ash adsorbent, sodium hydroxide modified fly ash adsorbent and high temperature modified fly ash adsorbent. In this paper, the effects of adsorbent dosage, adsorbent adsorption time, initial dye concentration, wastewater pH and temperature on dye adsorption were studied. The results showed that: the acid modified fly ash adsorbent had a good treatment effect on the dye; when the dosage of fly ash was 1.00 g, the adsorption time was 90 min, the pH of wastewater was 4, and the temperature was 45 °C, the decolorization rate of 60 mg/L methyl orange dye can reached more than 70%; when the dosage of fly ash was 0.20 g, the adsorption time was 60 min, the pH of wastewater was 3, and the temperature was 35 °C, the decolorization rate of 20 mg/L methyl orange dye can be achieved. The decolorization rate of Congo red can reached more than 80%.

Construction of novel electrochemical treatment systems for indigo wastewater and their performance

Purpose This study aims to evaluate the efficiency of metal electrode and electrolytes on the electroflocculation of indigo wastewater, produced by printing and dyeing factory, and to optimize the treatment system. Design/methodology/approach For effective purging, various types of metal electrodes (graphite, pure aluminum and stainless steel) and supporting electrolytes (sodium chloride and sodium sulfate) were selected for electroflocculation experiments. The decolorization rate and chemical oxygen demand (COD) removal rate were characterized. Findings The treatment effects of stainless steel and aluminum were similar, but the dissolution loss of aluminum and the production of flocs greatly limit its application. Electrolytes gave obvious effects to these systems. Sodium sulfate was better than sodium chloride, the decolorization rate was increased by 3.31%, the removal rate of COD in the solution was increased by 28.65% and the weight of flocculation precipitation was reduced by 0.214 g. Research limitations/implications The electrochemical treatment system was constructed to compare and analyze the influence of experimental parameters and to provide a reference for the actual treatment of indigo wastewater. Practical implications Electrochemical flocculation can remove the insoluble indigo solids and it plays a key role in wastewater treatment. Originality/value It is novel to optimize the combination of electrode and electrolyte to improve the efficiency of electroflocculation, which can be widely used in the actual wastewater treatment process.

Improving decolorization of dyes by laccase from Bacillus licheniformis by random and site-directed mutagenesis

Background Dye wastewater increases cancer risk in humans. For the treatment of dyestuffs, biodegradation has the advantages of economy, high efficiency, and environmental protection compared with traditional physical and chemical methods. Laccase is the best candidate for dye degradation because of its multiple substrates and pollution-free products. Methods Here, we modified the laccase gene of Bacillus licheniformis by error-prone PCR and site-directed mutagenesis and expressed in E. coli. The protein was purified by His-tagged protein purification kit. We tested the enzymatic properties of wild type and mutant laccase by single factor test, and further evaluated the decolorization ability of laccase to acid violet, alphazurine A, and methyl orange by spectrophotometry. Results Mutant laccase Lacep69and D500G were superior to wild type laccase in enzyme activity, stability, and decolorization ability. Moreover, the laccase D500G obtained by site-directed mutagenesis had higher enzyme activity in both, and the specific activity of the purified enzyme was as high as 426.13 U/mg. Also, D500G has a higher optimum temperature of 70 °C and temperature stability, while it has a more neutral pH 4.5 and pH stability. D500G had the maximum enzyme activity at a copper ion concentration of 12 mM. The results of decolorization experiments showed that D500G had a strong overall decolorization ability, with a lower decolorization rate of 18% for methyl orange and a higher decolorization rate of 78% for acid violet. Conclusion Compared with the wild type laccase, the enzyme activity of D500G was significantly increased. At the same time, it has obvious advantages in the decolorization effect of different dyes. Also, the advantages of temperature and pH stability increase its tolerance to the environment of dye wastewater.

GPCC catalyzed hydrogen peroxide for decolorization of C.I. Reactive Red 24 from simulated dyeing wastewater

A kind of gelatin protein copper complex (GPCC for short) was synthesized by us. GPCC acting as catalyst was applied to catalyzed hydrogen peroxide for decolorization of C.I. Reactive Red 24 from simulated dyeing wastewater. The influence of catalyzed hydrogen peroxide by GPCC on the decolorization of C.I. Reactive Red 24 from simulated dyeing wastewater was discussed. The optimum decolorization technology condition was optimized. And the effect of salt on decolorization of C.I. Reactive Red 24 in this catalytic system was also investigated. The results showed that hydrogen peroxide can be catalyzed by GPCC. In the catalytic system, the structure of C.I. Reactive Red 24 can be degraded and a high decolorization rate can be obtained in a wide pH range. In addition, the decolorization percentage and decolorization rate will be further improved when salt is present in the catalytic system.