Degradation of organic wastewater containing Cu-EDTA by Fe-C micro-electrolysis

In order to break the complex bonds and treat the organic wastewater containing heavy metal,such as Cu-EDTA solution,a novel process of Fe-C micro-electrolysis was proposed.Based on the principle of iron-carbon micro-electrolysis reaction,-OH radicals which were generated under the acidic aerobic condition during the micro-electrolysis process attacked to the organic groups of coordination compounds,which resulted in complex bonds breaking.Therefore copper（Ⅱ） ions were removed via nascent gelatinous ferric hydroxide and ferrous hydroxide,and EDTA was degraded by-OH radicals.Effects of pH value,temperature,electrolysis time and mass ratio of Fe to C on residual concentrations of total organic carbon（TOC） and Cu（Ⅱ） were studied.The mechanism of Fe-C micro-electrolysis was investigated and verified by analyzing micrographs of scanning electron microscopy（SEM）,energy dispersive analysis（EDS） and Fourier transform infrared spectrometry（FTIR）.The removal efficiency is optimal at pH value of 2.0,temperature of 25 °C,the mass ratio Fe to C of 0.02,and reaction time of 60 min.Under above conditions,the concentration of TOC decreases from 200 mg/L to 40.66 mg/L and the residual concentration of Cu（Ⅱ） decreases from initial 60 mg/L to 1.718 mg/L.

Micro-electrolysis technology for industrial wastewater treatment

Experiments were conducted to study the role of micro-electrolysis in removing chromaticity and COD and improving the biodegradability of wastewater from pharmaceutical, dye-printing and papermaking plants. Results showed that the use of micro-electrolysis technology could remove more than 90% of chromaticity and more than 50% of COD and greatly improved the biodegradability of pharmaceutical wastewater. Lower initial pH could be advantageous to the removal of chromaticity. A retention time of 30 minutes was recommended for the process design of micro-electrolysis. For the use of micro-electrolysis in treatment of dye-printing wastewater, the removal rates of both chromaticity and COD were increased from neutral condition to acid condition for disperse blue wastewater; more than 90% of chromaticity and more than 50% of COD could be removed in neutral condition for vital red wastewater.

Experimental study on micro-electrolysis technology for pharmaceutical wastewater treatment

Experiments were conducted to study the role of micro-electrolysis in removing chromaticity and COD and improving the biodegradability of pharmaceutical wastewater. The results showed that the use of micro-electrolysis technology could remove more than 90% of chromaticity and more than 50% of COD and greatly improved the biodegradability of pharmaceutical wastewater. Lower initial pH could be advantageous to the removal of chromaticity. A retention time of 30 minutes was recommended for the process design of micro-electrolysis.

Treatment of chitin-producing wastewater by micro-electrolysis-contact oxidization

The technique of micro-electrolysis-contact oxidization was exploited to treat chitin-producing wastewater. Results showed that Fe-C micro-electrolysis can remove about 30% CODcr, raise pH from 0.7 to 5.5. The CODcr removal efficiency by biochemical process can be more than 80%. During a half year抯 operation, the whole system worked very stably and had good results, as proved by the fact that every quality indicator of effluent met the expected discharge stan-dards; which means that chitin wastewater can be treated by the technique of micro-electrolysis, contact oxidization.

Degradation of Nitrobenzene Wastewater via Iron/Carbon Micro-electrolysis Enhanced by Ultrasound Coupled with Hydrogen Peroxide

The zero valent iron/granular active carbon(ZVI/GAC) micro-electrolysis enhanced by ultrasound(US) coupled with hydrogen peroxide(H_2O_2) was investigated for the deep degradation of nitrobenzene-containing wastewater. The results of scanning electron microscopy-energy dispersive X-rays analysis(SEM-EDS) demonstrated that continuously accelerated regeneration of ZVI and GAC in situ by US could improve the process for converting nitrobenzene(NB) to aniline(AN). H_2O_2 was decomposed catalytically by the byproduct Fe^(2+) ions generated in the micro-electrolysis process to hydroxyl radicals and the organic pollutants in the wastewater were finally mineralized to CO2 and H2O. Effects of the ZVI dosage, the ZVI/GAC mass ratio, the initial pH value and the H_2O_2 dosage on the efficiency for degradation of NB were studied in these experiments. The optimal operating conditions covered a ZVI dosage of 15 g/L, a ZVI/GAC mass ratio of 1:2,an initial pH value of 3 and a H_2O_2 dosage of 4 mL. In this case, the NB removal efficiency reached 97.72% and the total organic carbon(TOC) removal efficiency reached 73.42% at a NB concentration of 300 mg/L. The reduction of NB by USZVI/GAC followed the pseudo-first-order kinetics model, and the pseudo-first-order rate constants were given at different initial pH values. The reaction intermediates such as AN, benzoquinonimine, p-benzoquinone, p-nitrophenol and other organic acids were detected and a probable pathway for NB degradation has been proposed.

Treatment of naphthalene derivatives with iron-carbon micro-electrolysis

The degradation of five naphthalene derivatives in the simulated wastewater was investigated using the iron-carbon micro-electrolysis method.The optimal initial pH of solution and adsorption of iron-carbon and removal efficiency of the total organic carbon(TOC)were investigated.The results show that the removal efficiency of the naphthalene derivatives can reach 48.9%?92.6% and the removal efficiency of TOC is 42.8%?78.0% for the simulated wastewater with 200 mg/L naphthalene derivatives at optimal pH of 2.0?2.5 after 120 min treatment.The degradation of five naphthalene derivatives with the micro-electrolysis shows the apparent first-order kinetics and the order of removal efficiency of the naphthalene derivatives is sodium 2-naphthalenesulfonate,2-naphthol,2,7-dihydroxynaphthalene,1-naphthamine,1-naphthol-8-sulfonic acid in turn.It is illustrated that the substituents of the naphthalene ring can affect the removal efficiency of naphthalene due to their electron-withdrawing or electron-donating ability.

Treatment of Wastewater from Pharmaceutical Intermittent Production by Fe/C-Fenton-Hydrolysis Acidification-A/O Process

The design and running effect of treatment of wastewater from pharmaceutical intermittent production by iron-carbon（Fe/C）-Fentonhydrolysis acidification-anoxic/aerobic（A/O）process were introduced.The results of continuous operation showed that when the flow rate of the influent wastewater was 300 m^3/d,after the influent high-concentration wastewater（CODCrand NH4＋-N concentration were 35 000 and 1 000 mg/L,respectively）and medium-concentration wastewater（CODCrand NH4＋-N concentration were 1 500 and 100 mg/L,respectively）were treated by the process,CODCrand NH4＋-N concentration in the effluent decreased to 360-410 and 20-25 mg/L,respectively,and the quality of the effluent could meet the Grade III standard of Integrated Wastewater Discharge Standard（GB 8978-1996）.The combined process was proved to be an effective method to treat wastewater from pharmaceutical intermittent production,and its operation was stable.

Pretreatment of Herbicides Production Wastewater by Different Electrolyte Fillers

[Objective] The aim was to study the pretreatment effect of herbicides production wastewater by different types of micro-electrolysis filler.[Method] The research performed comparison on the effects of three types of micro-electrolysis filler treatment of pesticide wastewater by changing the role of time and p H.[Result] The results showed that the best treatment effect was spherical packing,followed by tooth filler;poor treatment effect and easy to harden were iron shavings.With pH of the influent of 2 and reaction time of 160 min,the removals of CODcr and chromaticity which was with spherical packing reached 24.79% and 97.5%;the removals of CODcr and chromaticity which Dentate micro-electrolysis filler treated reached21.74% and 93.75%.With pH of the influent at 3 and reaction time of 120 min,the removal of CODcr and chromaticity which was treated with iron ingot reached13.59% and 87.5%.[Conclusion] By comparison analysis,the spherical packing is better suited to handle wastewater.

Application of Fe^0/C/Clay ceramics for decoloration of synthetic Acid Red 73 and Reactive Blue 4 wastewater by micro-electrolysis

Dyes are common pollutants in textile wastewaters, and the treatment of the wastewater has now attracted much attention due to its wide application and low biodegradability. In this study, Fe^0/C/Clay ceramics, a kind of novel micro-electrolysis filler, were sintered and employed in a dynamic micro-electrolysis reactor for synthetic Acid Red 73 （AR73） and Reactive Blue 4 （RB4） wastewater treatment. The effects ofinfluent pH, hydraulic retention time （HRT）, and aeration on the decoloration efficiencies of AR73 and RB4 were studied. The optimum conditions for wastewater treatment were： AR73, influent pH of 4, HRT of 2 h and aeration; RB4, influent pH of 5, HRT of 6 h and aeration. Under the optimum conditions, decoloration efficiency of AR73 and RB4 wastewater was 96% and 83%, respectively. Results of UV-vis spectrum scanning demonstrated that the chromophores were broken. Continuous running tests showed that improvement of micro-electrolysis system with Fe^0/C/Clay ceramics for AR73 and RB4 synthetic wastewater treatment could avoid failure of micro-electrolysis reactor, which indicated great potential for the practical application of the ceramics in the field of actual industrial wastewater treatment.

Treatment of coking wastewater by a novel electric assisted micro-electrolysis filter

A newly designed electric assisted micro-electrolysis filter（E-ME） was developed to investigate its degradation efficiency for coking wastewater and correlated characteristics. The performance of the E-ME system was compared with separate electrolysis（SE） and micro-electrolysis（ME） systems. The results showed a prominent synergistic effect on COD removal in E-ME systems. Gas chromatography/mass spectrometry（GC–MS） analysis confirmed that the applied electric field enhanced the degradation of phenolic compounds.Meanwhile, more biodegradable oxygen-bearing compounds were detected. SEM images of granular activated carbon（GAC） showed that inactivation and blocking were inhibited during the E-ME process. The effects of applied voltage and initial p H in E-ME systems were also studied. The best voltage value was 1 V, but synergistic effects existed even with lower applied voltage. E-ME systems exhibited some p H buffering capacity and attained the best efficiency in neutral media, which means that there is no need to adjust p H prior to or during the treatment process. Therefore, E-ME systems were confirmed as a promising technology for treatment of coking wastewater and other refractory wastewater.

铁碳微电解–Fenton联合处理化学镀镍废水

为去除化学镀镍废水中的镍离子和氨氮,研究了铁碳微电解–Fenton联合处理技术。探讨了废水初始p H、铁屑投加量、铁屑与活性炭质量比、反应时间和H2O2投加量对处理效果的影响。结果表明,当初始p H为3,铁屑投加量为40 g/L,铁炭质量比为2∶1,H2O2/Fe2+为1.2(质量比),反应20 min后镍离子的去除率达99.8%以上,出水镍离子含量<0.1 mg/L,氨氮去除率达46.1%。

新型多元催化铁碳微电解填料的研制及应用

为了提高气田污水的处理效果,降低处理费用,研制了一种以高炉除尘灰为主要原料的新型多元催化铁碳微电解填料,该填料是在高炉除尘灰中添加一定量的活化剂、制孔剂与黏结剂,经过研磨制粉、搅拌混合、压制成型、晾晒与高温烧结等工艺制成。新型多元催化铁碳微电解填料用于气田污水处理时,以其对污水浊度的去除率为目标值,首先采用单因素实验法筛选出对气田污水浊度去除率影响较大的配方与制备工艺参数指标;再利用Design Expert 10的Box-Behnken软件,对活化剂、制孔剂、黏结剂的含量、烧结温度等设计了实验方案、给出了优化模型;最后依据优化成果,制备了新型多元催化铁碳微电解填料。该填料中高炉除尘灰的用量高达74%,与常规铁碳微电解填料相比,去除率平均提高了12.74%。新型多元催化铁碳具有活性强、净化效果好的优点,而且制造成本低,可实现工业固废物的绿色循环利用。

High-gravity intensified iron-carbon micro-electrolysis for degradation of dinitrotoluene

The application of iron–carbon(Fe–C)micro-electrolysis to wastewater treatment is limited by the passivation potential of the Fe–C packing.In order to address this problem,high-gravity intensified Fe–C micro-electrolysis was proposed in this study for degradation of dinitrotoluene wastewater in a rotating packed bed(RPB)using commercial Fe–C particles as the packing.The effects of reaction time,high-gravity factor,liquid flow rate and initial solution pH were investigated.The degradation intermediates were determined by gas chromatography-mass spectrometry,and the possible degradation pathways of nitro compounds by Fe–C micro-electrolysis in RPB were also proposed.It is found that under optimal conditions,the removal rate of nitro compounds reaches 68.4%at 100 min.The removal rate is maintained at approximately 68%after 4 cycles in RPB,but it is decreased substantially from 57.9%to 36.8%in a stirred tank reactor.This is because RPB can increase the specific surface area and the renewal of the liquid–solid interface,and as a result the degradation efficiency of Fe–C micro-electrolysis is improved and the active sites on the Fe–C surface can be regenerated for continuous use.In conclusion,high-gravity intensified Fe–C micro-electrolysis can weaken the passivation of Fe–C particles and extend their service life.

Fe/C micro electrolysis and Fenton oxidation process for the removal of recalcitrant colored pollutants from mid-stage pulping effluent

The pulp and paper industry produces a large amount of colored effluent in the pulping,bleaching,and papermaking processes.The wastewater from the pulp washing and bleaching stages is also known as mid-stage pulping effluent,which is difficult to treat due to its toxicity and dark dolor.This paper reports a novel Fe/C micro-electrolysis process for the treatment of the mid-stage pulping effluent.Results show that this process is effective in removing the color under optimal reaction conditions.Scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FTIR)analyses indicate that the colored pollutants were removed from the wastewater in the Fe/C micro-electrolysis by adsorption,collection and filtration mechanisms.The Fe2+ions produced in the micro-electrolysis process functioned as Fenton’s reagents with H2O2 in the follow-up oxidation stage,which enhanced the removal of chemical oxygen demand(COD)and color.