微波诱导AC/Cu、AC/Fe催化非均相Fenton 反应催化降解垃圾渗滤液

采用活性炭载体负载Cu、Fe为催化剂,在微波诱导作用下,对垃圾渗滤液污染物进行降解。实验结果表明,活性炭负载金属前经适当浓度硝酸浸泡处理后,催化剂对COD去除率提高可超过15%,过高硝酸盐浓度对COD去除有不利影响;催化剂对COD去除率随Cu、Fe金属负载量增加呈先增加后降低的趋势,催化剂对Cu、Fe的最佳负载量分别为质量百分比2.11%和1.12%。对于AC-Cu体系,在初始pH=3,H2O2投加量为4.98×103mg/L,催化剂用量为5.0×103mg/L,420 W功率下微波辐射10 min时,垃圾渗滤液COD去除率可达到84.13%;对于AC-Fe体系,当H2O2投加量为0.33×103mg/L,催化剂AC-Fe用量为2.0×104mg/L,420 W功率下微波作用10 min时,垃圾渗滤液COD去除率为60.16%。分析2种催化剂对COD去除差异的原因,可能是催化剂AC-Cu表面单分子分布的阈值比AC-Fe高。降解液的pH值对AC-Cu体系、AC-Fe体系COD去除影响存在拐点,最高COD去除率点对应的降解液pH值为3。微波辐射功率较低时,体系COD去除率随辐射功率增加而增加;辐射功率较高时,高温下垃圾渗滤液中有机硫化物分解成小分子硫化物,对催化剂活性存在一定抑制作用。     

Effect of deposit age on adsorption and desorption behaviors of ammonia nitrogen on municipal solid waste

Ammonia nitrogen pollution control is an urgent issue of landfill. This research aims to select an optimal refuse for ammonia nitrogen removal in landfill from the point of view of adsorption and desorption behavior. MSW (municipal solid waste) samples which deposit ages were in the range of 5 to 15 years (named as R₁₅, R₁₁, R₇, and R₅) were collected from real landfill site. The ammonia nitrogen adsorption behaviors of MSW including equilibrium time, adsorption isotherms, and desorption behaviors including equilibrium time were determined. Furthermore, the effects of pH, OM, Cu(II), Zn(II), and Pb(II) on adsorption and desorption behavior of ammonia nitrogen were conducted by orthogonal experiment. The equilibrium time of ammonia nitrogen adsorption by each tested MSW was very short, i.e., 20 min, whereas desorption process needed 24 h and the ammonia nitrogen released from refuses was much lesser than that adsorbed, i.e., accounted for 3.20 % (R₁₅), 14.32 % (R₁₁), 20.59 % (R₇), and 20.50 % (R₅) of each adsorption quantity, respectively. The maximum adsorption capacity estimated from Langmuir isotherm appeared in R₁₅-KCl, i.e., 25,000 mg kg^?1. The best condition for ammonia nitrogen removal from leachate was pH >7.5, OM 23.58 %, Cu(II) <5 mg L^?1, Zn(II) <10 mg L^?1, and Pb(II) <1 mg L^?1. Ammonia nitrogen in landfill leachate could be quickly and largely absorbed by MSW but slowly and infrequently released. The refuse deposited for 15 years could be a suitable material for ammonia nitrogen removal.     

超声波-膜生物法联合处理垃圾焚烧厂渗滤液

采用超声波-膜生物法(MBR)联合处理垃圾渗滤液,探讨了超声波辐射时间和MBR的水力负荷对COD、NH3-N和TP去除的影响。结果表明,(1)超声波单独处理时,超声波辐射时间在30～90 s时,COD、NH3-N最大增加率分别34.31%、3.36%,而对TP的去除没有影响;(2)超声波-膜生物(MBR)联合处理时,超声波辐射时间为300 s,MBR的水力负荷为6.4 L/(m2.d)时,COD、NH3-N和TP的最佳去除率分别为92.20%、80.10%和91.12%;MBR的水力负荷为12.8 L/(m2.d),超声波辐射时间在5～20 min时,COD、NH3-N的最佳去除率分别为92.34%、79.93%,TP的浓度低于0.2 mg/L;MBR反应时间为7 h,超声波辐射时间为5～20 min,与未进行超声波辐射处理(超声波辐射时间为0 min)相比,COD、NH3-N的去除率增加了11.37%、15.26%;超声波预处理有助于提高后续MBR对COD、NH3-N的去除作用。     

Hybrid zero valent iron (ZVI)/H2O2 oxidation process for landfill leachate treatment with novel nanosize metallic calcium/iron composite

A novel nanosize metallic calcium/iron dispersed reagent was synthesized and tested as coagulant/catalyst in a hybrid zero valent iron (ZVI)/H₂O₂ oxidation process to treat leachate. Two different types of leachates, one from municipal solid waste (MSW) tipping hall (MSWIL) and second from an MSW landfill site (MSWLL), were collected and characterized. The morphology, elemental composition, and mineral phases of the nano-Ca/CaO and nano-Fe/Ca/CaO were characterized by scanning electron microscopy–electron dispersive spectroscopy (SEM-EDS) and x-ray powder diffraction (XRD) analysis. The coagulation process with 2.5 g L^?1 nano-Ca/CaO attained 64.0, 56.0, and 20.7% removal of color, chemical oxygen demand (COD), and total suspended solids (TSS) in MSWLL. With only 1.0 g L^?1 of nano-Fe/Ca/CaO, relatively high color, COD and TSS removal was achieved in MSWLL at 67.5, 60.2, and 37.7%, respectively. The heavy metal removal efficiency reached 91–99% after treatment with nano-Fe/Ca/CaO in both leachate samples. The coupling process, using 1.0 g L^?1 of nano-Fe/Ca/CaO and 20 mM H₂O₂ doses, achieved enhancement removal of color, COD, and TSS, up to 95%, 96%, and 66%, respectively, without initial pH control. After this treatment, the color, COD, TSS, and heavy metals were significantly decreased, fitting the Korean discharge regulation limit. A hybrid coupled zero valent iron (ZVI)/H₂O₂ oxidation process with novel nanosized metallic calcium/iron dispersed reagent proved to be a suitable treatment for dealing with leachate samples.

Implications: Conventional treatments (biological or physicochemical) are not sufficient anymore to reach the level of purification needed to fully reduce the negative impact of landfill leachates on the environment. This implies that new treatment alternatives species must be proposed. A coupled zero valent iron (ZVI)/H₂O₂ oxidation process proved to be a suitable treatment for dealing with leachate samples. Coagulation with nFe/Ca/CaO allows 91–99% of heavy metals removal. The coupled coagulation–oxidation process by nFe/Ca/CaO reveals excellent ability to treat leachate. After coupled treatment the color, COD, and TSS were also much lower than the discharge regulation limit.     

混凝与Fenton联用处理垃圾渗滤液的效能及成本

为对混凝/Fenton工艺与Fenton/混凝工艺处理垃圾渗滤液的效果和成本进行比较,分别对年轻渗滤液和老龄渗滤液原液按照混凝/Fenton工艺与Fenton/混凝工艺2种技术路线进行处理。实验结果表明,Fenton试剂对年轻垃圾渗滤液和老龄垃圾渗滤液COD去除率最高的反应条件为pH=3.5、H2O2和Fe2+的摩尔比为6、H2O2和渗滤液原液的COD质量比为3、反应时间4 h;在PAC与渗滤液原液的COD质量比为0.6时,PAC混凝对渗滤液原液的COD去除率最高。在对渗滤液COD去除率最高的Fenton反应和PAC混凝反应条件下,混凝/Fenton工艺对年轻渗滤液和老龄渗滤液的COD去除率分别为90.56%和86.56%;Fenton/混凝工艺对年轻渗滤液和老龄渗滤液的COD去除率分别为89.99%和85.99%,2种技术路线对渗滤液COD的去除率相差不大,但先PAC混凝后Fenton氧化工艺比先Fenton后混凝工艺每t节省62.6元,是更优化的渗滤液处理工艺。     

A Novel Design for Anaerobic Chemical Oxygen Demand and Nitrogen Removal from Leachate in a Semiaerobic Landfill

Abstract

The removal capacity of carbon and nitrogen from an artificial leachate was evaluated by using laboratory-scale columns, and a design was proposed to remove nitrogen more efficiently from a semiaerobic landfill. Five columns (i.e., two artificial municipal waste columns under anaerobic and semiaerobic conditions, an artificial construction waste column under semiaerobic conditions, and two crushed stone columns under anaerobic and semiaerobic conditions) were used. The influent load rates of organics [g chemical oxygen demand (COD)/m³ ·day], NH₄ ⁺, NO₃ ^?, and aeration conditions for the columns were varied, and the removal capacities of the columns for COD, NH₄ ⁺-N, and NO₃ ^?-N were measured.

Among the packed column materials, crushed stone was shown to be most effective in removing COD, NH₄ ⁺-N, and NO₃ ^?-N from artificial leachate. Average removal rates of crushed column under the semiaerobic condition (column D) for COD and NH₄ ⁺-N were estimated at about 150 g COD/m³·day and 20 g COD/m³ ·day, while those of crushed column under anaerobic condition (column E) for COD and NO₃ ^?-N at about 400 and 150 g COD/m³ ·day, respectively. It also was found that denitrification and nitrification reactions in column D occurred at the same time, and the ratio of denitrification to nitrification was estimated to be about 80%. Therefore, an anaerobic structure, which could be attached to the bottom of a main pipe in a semiaerobic landfill, is suggested to remove nitrogen and organic substances more effectively.     

Biostyr曝气生物滤池处理城市污水的沿程生化特性

青岛市麦岛污水处理厂采用曝气生物滤池(BAF)处理城市污水,以稳定运行的Biostyr为研究载体,考察滤池COD、NH3-N、SS和细菌数量等生化特性的沿程变化.结果表明,在气水比为4∶1～5∶1、进水COD负荷为2.5 ～3.7 kg/(m3·d)、进水NH3-N负荷为0.18～0.57 kg/(m3·d)时,滤池对COD的降解主要在150 cm填料以下处,COD的去除率可达58.9％;NH3-N去除率沿滤柱高度的变化与COD有所不同,在100 cm以下填料处,NH3-N的去除率仅为3.6％,在100 ～350 cm填料之间,NH3-N的去除率增加迅速,可达56.1％;对SS的去除主要发生在100 cm填料以下,去除率达51.7％.     

矿化污泥生物反应器处理生活垃圾填埋场老龄渗滤液

经长时间稳定化形成的矿化污泥中,含有种类丰富和数量繁多的降解性微生物,具有处理渗滤液的潜力。建立3个矿化污泥生物反应器,即C1(粉煤灰0%),C2(粉煤灰9.1%),C3(粉煤灰16.7%),以处理垃圾填埋场老龄渗滤液。在单级矿化污泥反应器中,当进水COD和NH3-N分别约为1350和900 mg/L时,水力负荷为17.7～70.8 L/(m3.d),COD去除率可超过65%,氨氮的去除率可超过94%。粉煤灰的加入一定程度上降低了COD去除率,但有助于氨氮的去除。在二级矿化污泥生物反应器中(即C3～C1串联),水力负荷为35.4 L/(m3.d)的工况下,当COD、TOC、IC和NH3-N分别为1 500～2 500,500～900,1 200～1 600和1 200～1 450 mg/L时,出水可达到COD<300 mg/L,TOC<180 mg/L,IC<100 mg/L,NH3-N<5 mg/L。但是,矿化污泥生物反应器对渗滤液总氮的去除率较低,仅为20%左右。     

Electrooxidation of industrial wastewater containing 1,4-dioxane in the presence of different salts

The treatment of 1,4-dioxane solution by electrochemical oxidation on boron-doped diamond was studied using a central composite design and the response surface methodology to investigate the use of SO₄ ^2? and HCO₃ ^? as supporting electrolytes considering the applied electric current, initial chemical oxygen demand (COD) value, and treatment time. Two industrial effluents containing bicarbonate alkalinity, one just carrying 1,4-dioxane (S1), and another one including 1,4-dioxane and 2-methyl-1,3-dioxolane (S2), were treated under optimized conditions and subsequently subjected to biodegradability assays with a Pseudomonas putida culture. Electrooxidation was compared with ozone oxidation (O₃) and its combination with hydrogen peroxide (O₃/H₂O₂). Regarding the experimental design, the optimal compromise for maximum COD removal at minimum energy consumption was shown at the maximum tested concentrations of SO₄ ^2? and HCO₃ ^? (41.6 and 32.8 mEq L^?1, respectively) and the maximum selected initial COD (750 mg L^?1), applying a current density of 11.9 mA cm^?2 for 3.8 h. Up to 98 % of the COD was removed in the electrooxidation treatment of S1 effluent using 114 kWh per kg of removed COD and about 91 % of the COD from S2 wastewater applying 49 kWh per kg of removed COD. The optimal biodegradability enhancement was achieved after 1 h of electrooxidation treatment. In comparison with O₃ and O₃/H₂O₂ alternatives, electrochemical oxidation achieved the fastest degradation rate per oxidant consumption unit, and it also resulted to be the most economical treatment in terms of energy consumption and price per unit of removed COD.     

Cr(VI) and COD removal from landfill leachate by polyculture constructed wetland at a pilot scale

Four subsurface horizontal-flow constructed wetlands (CWs) at a pilot scale planted with a polyculture of the tropical plants Gynerium sagittatum (Gs), Colocasia esculenta (Ce) and Heliconia psittacorum (He) were evaluated for 7 months. The CW cells with an area of 17.94 m² and 0.60 m (h) each and 0.5 m of gravel were operated at continuous gravity flow (Q?=?0.5 m³ day^?1) and a theoretical HRT of 7 days each and treating landfill leachate for the removal of filtered chemical oxygen demand (COD_f), BOD₅, TKN, NH₄ ⁺, NO₃ ^?, PO₄ ^3?–P and Cr(VI). Three CWs were divided into three sections, and each section (5.98 m²) was seeded with 36 cuttings of each species (plant density of six cuttings per square metre). The other unit was planted randomly. The final distributions of plants in the bioreactors were as follows: CW I (He-Ce-Gs), CW II (randomly), CW III (Ce-Gs-He) and CW IV (Gs-He-Ce). The units received effluent from a high-rate anaerobic pond (BLAAT®). The results show a slightly alkaline and anoxic environment in the solid-liquid matrix (pH?=?8.0; 0.5–2 mg L^?1 dissolved oxygen (DO)). COD_f removal was 67 %, BOD₅ 80 %, and TKN and NH₄ ⁺ 50–57 %; NO₃ ^? effluents were slightly higher than the influent, PO₄ ^3?–P (38 %) and Cr(VI) between 50 and 58 %. CW IV gave the best performance, indicating that plant distribution may affect the removal capacity of the bioreactors. He and Gs were the plants exhibiting a translocation factor (TF) of Cr(VI) >1. The evaluated plants demonstrated their suitability for phytoremediation of landfill leachate, and all of them can be categorized as Cr(VI) accumulators. The CWs also showed that they could be a low-cost operation as a secondary system for treatment of intermediated landfill leachate (LL).     

微波法制备污泥活性炭研究

采用微波加热法,以污水厂剩余污泥为原料,磷酸为污泥活化剂制备污泥活性炭.微波功率、辐照时间和磷酸浓度对污泥活性炭吸附性能具有显著影响,在最佳工艺条件微波功率480 W、辐照时间315 s和磷酸浓度40%条件下制得的活性炭碘值301 mg/g,比表面积168 m2/g,污泥中重金属绝大部分被固化.与传统商品炭相比,污泥炭孔隙结构以中孔为主.利用该活性炭处理城市生活污水处理厂出水,COD去除率可达87%以上,污泥炭的吸附等温线用Langmuir等温吸附模型进行描述.     

Organic-coated nanoparticulate zero valent iron for remediation of chemical oxygen demand (COD) and dissolved metals from tropical landfill leachate

The use of nanoparticulate zero valent iron (NZVI) in the treatment of inorganic contaminants in landfill leachate and polluted plumes has been the subject of many studies, especially in temperate, developed countries. However, NZVI’s potential for reduction of chemical oxygen demand (COD) and treatment of metal ion mixtures has not been explored in detail. We investigated the efficiency of NZVI synthesized in the presence of starch, mercaptoacetic, mercaptosuccinic, or mercaptopropenoic acid for the reduction of COD, nutrients, and metal ions from landfill leachate in tropical Sri Lanka. Synthesized NZVI were characterized with X-ray diffraction (XRD), transmission electron microscopy, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), thermal gravimetric analysis, Fourier transform infrared spectroscopy (FTIR) and Brunauer–Emmett–Teller. Of the samples tested, Starch-NZVI (S-NZVI) and mercaptoacetic-NZVI (MA-NZVI) performed well for treatment both COD and metal mixture. The removal percentages for COD, nitrate-nitrogen, and phosphate from S-NZVI were 50, 88, and 99 %, respectively. Heavy metal removal was higher in S-NZVI (>95 %) than others. MA-NZVI, its oxidation products, and functional groups of its coating showed the maximum removal amounts for both Cu (56.27 mg g^?1) and Zn (28.38 mg g^?1). All mercapto-NZVI showed well-stabilized nature under FTIR and XRD investigations. Therefore, we suggest mercapto acids as better agents to enhance the air stability for NZVI since chemically bonded thiol and carbonyl groups actively participation for stabilization process.     

Low-cost adsorbents from bio-waste for the removal of dyes from aqueous solution

Activated carbons (ACs) were developed from bio-waste materials like rice husk and peanut shell (PS) by various physicochemical activation methods. PS char digested in nitric acid followed by treatment at 673 K resulted in high surface area up to ～585 m²/g. The novelty of the present study is the identification of oxygen functional groups formed on the surface of activated carbons by infrared and X-ray photoelectron spectroscopy and quantification by using temperature programmed decomposition (TPD). Typical TPD data indicated that each activation method may lead to varying amounts of acidic and basic functional groups on the surface of the adsorbent, which may be a crucial factor in determining the adsorption capacity. It was shown that ACs developed during the present study are good adsorbents, especially for the removal of a model textile dye methylene blue (MB) from aqueous solution. As MB is a basic dye, H₂O₂-treated rice husk showed the best adsorption capacity, which is in agreement with the acidic groups present on the surface. Removal of the dye followed Langmuir isotherm model, whereas MB adsorption on ACs followed pseudo-second-order kinetics.     

Removal mechanisms and kinetics of trace tetracycline by two types of activated sludge treating freshwater sewage and saline sewage

Understanding the removal mechanisms and kinetics of trace tetracycline by activated sludge is critical to both evaluation of tetracycline elimination in sewage treatment plants and risk assessment/management of tetracycline released to soil environment due to the application of biosolids as fertilizer. Adsorption is found to be the primary removal mechanism while biodegradation, volatilization, and hydrolysis can be ignored in this study. Adsorption kinetics was well described by pseudo-second-order model. Faster adsorption rate (k ₂?=?2.04?×?10^?2?g?min^?1?μg^?1) and greater adsorption capacity (q _e?=?38.8 μg?g^?1) were found in activated sludge treating freshwater sewage. Different adsorption rate and adsorption capacity resulted from chemical properties of sewage matrix rather than activated sludge surface characteristics. The decrease of tetracycline adsorption in saline sewage was mainly due to Mg²⁺ which significantly reduced adsorption distribution coefficient (K _d) from 12,990?±?260 to 4,690?±?180 L?kg^?1. Species-specific adsorption distribution coefficients followed the order of $ K_{\mathrm{d}}^{{ + 00}} \gg K_{\mathrm{d}}^{{ + - 0}} > K_{\mathrm{d}}^{{ + - - }} $ . Contribution of zwitterionic tetracycline to the overall adsorption was >90 % in the actual pH range in aeration tank. Adsorption of tetracycline in a wide range of temperature (10 to 35 °C) followed the Freundlich adsorption isotherm well.     

Adsorption of ammonium on biochar prepared from giant reed

Giant reed was used as precursor for making biochar in order for the adsorption of NH₄ ⁺–N from aqueous solution. And the adsorption of the product to NH₄ ⁺–N was examined. The surface features of biochar were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy/energy dispersive spectrometer (SEM-EDS), and X-ray diffraction (XRD). XRD patterns showed several peaks and correspond to the high amount of crystalline material. The crystals contain KCl, K₂O, CaO, MgO, and SiO and possess high surface area which enhances adsorption. The influence of different parameters such as initial concentration, adsorption time, pH, and ionic strength has been carried out. The adsorption could reach equilibrium through 24 h reaction and had the best adsorption amount at the solution pH values from 7 to 9. The cation has great influence on the adsorption of NH₄ ⁺–N, whereas the anion exerted a weaker effect. The adsorption followed pseudo-first-order and pseudo-second-order models. And the intraparticle diffusion and desorption studies further elucidated that the mechanism of adsorption on the product was ion exchange. The product equilibrium data was well described by the Langmuir and Freundlich model. The maximum adsorption capacities were 1.490 mg/g. Biochar derived from giant reed at 500 °C was suggested as a promising adsorbent for the removal of NH₄ ⁺–N from slightly polluted wastewater.     

Synthetic olive mill wastewater treatment by Fenton’s process in batch and continuous reactors operation

Degradation of total phenol (TPh) and organic matter, (expressed as total organic carbon TOC), of a simulated olive mill wastewater was evaluated by the Fenton oxidation process under batch and continuous mode conditions. A mixture of six phenolic acids usually found in these agro-industrial wastewaters was used for this purpose. The study focused on the optimization of key operational parameters of the Fenton process in a batch reactor, namely Fe²⁺ dosage, hydrogen peroxide concentration, pH, and reaction temperature. On the assessment of the process efficiency, > 99% of TPh and > 56% of TOC removal were attained when [Fe²⁺] = 100 ppm, [H₂O₂] = 2.0 g/L, T = 30 °C, and initial pH = 5.0, after 300 min of reaction. Under those operational conditions, experiments on a continuous stirred-tank reactor (CSTR) were performed for different space-time values (τ). TOC and TPh removals of 47.5 and 96.9%, respectively, were reached at steady-state (for τ = 120 min). High removal of COD (> 75%) and BOD₅ (> 70%) was achieved for both batch and CSTR optimum conditions; analysis of the BOD₅/COD ratio also revealed an increase in the effluent’s biodegradability. Despite the high removal of lumped parameters, the treated effluent did not met the Portuguese legal limits for direct discharge of wastewaters into water bodies, which indicates that coupled chemical-biological process may be the best solution for real olive mill wastewater treatment.     

高浓度钻井废水的混凝-催化氧化处理

以华北油田某深井的高浓度钻井废水(COD高达14 460.0 mg/L)为研究对象,提出了酸化-混凝-催化氧化-吸附的组合处理工艺。重点研制了钻井废水催化氧化处理催化剂(镍基催化剂),通过实验确定了最佳工艺参数条件。着重考察了催化氧化处理的工艺条件,在pH值为4,次氯酸钙投加量为4.4 g/L,催化剂投加量为1.6 g/L的条件下COD降至403.5 mg/L,进一步吸附处理后COD降至139.9 mg/L、色度为30倍、石油类含量为3.8 mg/L、pH为8.0和SS浓度为52mg/L,最终出水水质达到《污水综合排放标准》(GB 8978-1996)二级标准,处理成本为84.8元/m3。     

Removal of algal blooms from freshwater by the coagulation–magnetic separation method

This research investigated the feasibility of changing waste into useful materials for water treatment and proposed a coagulation–magnetic separation technique. This technique was rapid and highly effective for clearing up harmful algal blooms in freshwater and mitigating lake eutrophication. A magnetic coagulant was synthesized by compounding acid-modified fly ash with magnetite (Fe₃O₄). Its removal effects on algal cells and dissolved organics in water were studied. After mixing, coagulation, and magnetic separation, the flocs obtained from the magnet surface were examined by SEM. Treated samples were withdrawn for the content determination of chlorophyll-a, turbidity, chemical oxygen demand (COD), total nitrogen, and total phosphorus. More than 99 % of algal cells were removed within 5 min after the addition of magnetic coagulant at optimal loadings (200 mg L^?1). The removal efficiencies of COD, total nitrogen, and phosphorus were 93, 91, and 94 %, respectively. The mechanism of algal removal explored preliminarily showed that the magnetic coagulant played multiple roles in mesoporous adsorption, netting and bridging, as well as high magnetic responsiveness to a magnetic field. The magnetic–coagulation separation method can rapidly and effectively remove algae from water bodies and greatly mitigate eutrophication of freshwater using a new magnetic coagulant. The method has good performance, is low cost, can turn waste into something valuable, and provides reference and directions for future pilot and production scale-ups.     

混凝+芬顿法对中晚期垃圾渗滤液色度去除

垃圾渗滤液经一般生化处理后色度很大。对混凝和芬顿法结合深度处理垃圾渗滤液对色度去除进行了研究。混凝段通过中心复合设计(简称CCD)和响应面方法(简称RSM)分析了混凝的色度去除率的响应特征,建立了实际因素的最终方程模型:Y(色度去除率,%)=-553.40+73.74A+229.06B+0.38AB-34.16A2-22.67B2,(Y、A、B分别代表色度去除率、投加量和pH)并对絮凝条件进行优化,得到混凝反应的最佳优化条件:投加量1.11 g/L,pH 5.06,及在此条件下的去除率67.2%。在芬顿段,将芬顿反应对水中亲水性有机物相对含量(UV254)与对色度的去除特征相结合进行了研究,证明色度的去除跟该类有机物的去除有关,色度去除率最优值条件选择为H2O2/COD=1.0,Fe2+/H2O2=0.35∶1,而初始pH=2.5时对色度的去除达到99%以上。整个工艺出水可达到达标排放标(GB16889-2008)。     

Efficient degradation of rhodamine B using modified graphite felt gas diffusion electrode by electro-Fenton process

The electro-Fenton (EF) process treatment of 0.1-M (rhodamine B) RhB solution was studied with different graphite cathode materials, and graphite felt (GF) was selected as a promising material in further investigation. Then, the degradation performances of gas diffusion electrode (GDE) and graphite felt (GF) were compared, and GDE was confirmed to be more efficient in RhB removal. The operational parameters such as Fe²⁺ dosage and current density were optimized, and comparison among different modified methods—polytetrafluoroethylene-carbon black (PTFE-CB), polytetrafluoroethylene-carbon nanotube (PTFE-CNT), electrodeposition-CB, and electrodeposition-CNT—showed 98.49 % RhB removal by PTFE-CB-modified cathode in 0.05 M Na₂SO₄ at a current density of 50 A/m² and an air flow rate of 1 L/min after 20 min. Meanwhile, after cathode modified by PTFE-CB, the mineralization efficiency and mineralization current efficiency performed absolutely better than the pristine one. Cyclic voltammograms, SEM images, contact angles, and BET surface area were carried out to demonstrate stronger current responses and higher hydrophilicity of GF after modified. The value of biochemical oxygen demand/chemical oxygen demand (BOD₅/COD) increased from 0.049 to 0.331 after 90-min treatment, suggesting the solution was biodegradable, and the modified cathode was confirmed to be stable after ten circle runs. Finally, a proposed degradation pathway of RhB was put forward.