Removal of Cr(VI) and humic acid by using TiO2 photocatalysis

The removal efficiencies of Cr(VI) and HA, using a TiO(2)-mediated photocatalytic process, were investigated with variations in the pH, TiO(2) dosage and Cr(VI)/HA ratio. During the photocatalytic reaction, the total removal of Cr(VI) occurred through adsorption onto TiO(2), as well as its reduction to Cr(III). However, oxidation and adsorption were identified as important removal processes for the treatment of HA. Due to the anionic type adsorption onto TiO(2) and its acid-catalyzed photocatalytic reduction, the removal of Cr(VI) decreased with increasing pH, while that of HA increased with increasing pH. The TiO(2) dosage was also an important parameter for the removal of Cr(VI). As the TiO(2) dosage was increased to 2.5 g l(-1), the removal of Cr(VI) was continuously enhanced, but decreased at dosages above 3 g l(-1) due to the increased blockage of the incident UV light used for the photocatalytic reaction. The removal of Cr(VI) was greatly enhanced when the system contained both HA and Cr(VI) compared to Cr(VI) alone. Also, the removal of HA was greatly enhanced when the system contained both HA and Cr(VI) compared to HA alone. The removal of Cr(VI) was continuously enhanced as the HA concentration gradually increased; however, no further increase was observed above 20 mg l(-1) HA due to the increased absorption of the UV light. This result supports that the photocatalytic reaction, with illuminated TiO(2), could be applied to more effectively treat wastewater containing both Cr(VI) and HA than that containing a single species only.     

Photochemical degradation of methylparathion in the presence of humic acid

Photochemical degradation of methylparathion (O,O,-dimethyl O-4 nitrophenylphosphorothioate) in the presence of humic acid between pH 2 and 7 was monitored by differential pulse polarography. Humic acid was not electro-active under the experimental conditions used in this study. Only the pesticide and its main degradation product at pH 2 exhibited polarographic signals. Photolysis of methylparathion in acid media was sensitized by humic acid since the pesticide did not degrade in the absence of this compound. Methylparathion degradation in the presence of humic acid was observed at each of the studied pHs. The reaction was first-order with rate constant values ranging from 2 × 10^?3 to 6.3 × 10^?3 min^?1.     

Photochemical degradation of methylparathion in the presence of humic acid

Photochemical degradation of methylparathion (O,O,-dimethyl O-4 nitrophenylphosphorothioate) in the presence of humic acid between pH 2 and 7 was monitored by differential pulse polarography. Humic acid was not electro-active under the experimental conditions used in this study. Only the pesticide and its main degradation product at pH 2 exhibited polarographic signals. Photolysis of methylparathion in acid media was sensitized by humic acid since the pesticide did not degrade in the absence of this compound. Methylparathion degradation in the presence of humic acid was observed at each of the studied pHs. The reaction was first-order with rate constant values ranging from 2 x 10(-3) to 6.3 x 10(-3) min(-1).     

天然沸石去除腐殖酸和氨氮的研究

采用改性的浙江缙云天然斜发沸石,进行去除氨氮和腐殖酸的研究。腐殖酸对氨氮的去除有影响,含量越高。影响也越大。沸石主要去除大分子量的腐殖酸,对小分子量的腐殖酸去除效果较差。由于大分子腐殖酸会干扰氨氮的去除,去除大分子的腐殖酸有助于提高沸石去除氨氮的效果。     

负载CoO催化粒子电极的制备及其对腐殖酸的降解

以活性炭粉为载体,钴氧化物为催化活性组分,经造粒后制得PAC-Co催化粒子电极,研究了用于腐殖酸（HA）降解的PAC-Co催化粒子电极的制备条件,并采用扫描电子显微镜、X射线衍射和比表面积分析仪等对粒子电极进行表征。结果显示,焙烧温度600℃、焙烧时间2 h、Co（NO3）2浸渍液浓度0.1 mol·L-1为PAC-Co最佳制备条件。在I=0.2 A、进水流量9 mL·min-1、Na2SO4电解质0.01 mol·L-1、pH=7条件下,对于初始COD0=200 mg·L-1的模拟HA废水,反应70 min后,PAC-Co对UV254、色度及COD的去除分别达到95.09、97.84与91.45%,去除率均高于普通活性炭颗粒所制备的GAC-Co粒子电极。     

旋转盘反应器光催化降解苯酚废水动力学

采用旋转盘反应器(SDR)降解苯酚废水,对苯酚初始浓度、溶液pH值、H2O2的添加对其光催化降解动力学的影响进行了研究。结果表明,SDR内的光催化降解动力学特征符合一级反应动力学规律。苯酚初始浓度越低,反应速率常数k值越大;溶液pH=2时的降解速率高于其他pH值;H2O2的协同作用使苯酚的降解速率明显提高,其速率常数k值为未添加H2O2时的78倍。     

超声波-光催化联合降解苯酚废水研究

超声降解和光催化降解均为自由基历程的高级氧化技术,同时,超声空化能够改善传质效果,因此,二者耦合能否产生协同效果是值得研究的。本文考察了苯酚溶液的超声降解、光降解、光催化降解、超声-光催化降解以及温度对光降解和光催化降解的影响。结果表明,40kHz,0.4w/cm2的超声波对苯酚没有明显的降解作用,而对光催化降解只有轻微的促进作用。光降解和光催化降解的过程曲线显著不同,但温度对二者均有显著的促进作用。     

紫外光催化耦合化学絮凝工艺及其对腐殖酸抑制污泥发酵产酸的缓解效果

污泥热水解过程中释放的腐殖酸对厌氧发酵产挥发性脂肪酸存在抑制作用。针对该问题,采用单独使用紫外光催化或添加CaCl₂化学絮凝及2种方法的耦合,以达到腐殖酸改性和去除的目的。结果表明：单独采用紫外光催化,腐殖酸的去除率仅达到17.68%,污泥发酵产酸率由原本的17.72%提高至20.73%;单独采用化学絮凝,腐殖酸的去除率为35.21%,发酵产酸率为27.96%;光催化耦合CaCl₂化学絮凝后,腐殖酸胶体的Zeta电位上升至−1.76 mV,腐殖酸的去除率可达68.50%,污泥发酵产酸效率提高至31.64%。其主要原因是,光催化使得腐殖酸的荧光基团发生了脱落和重排,大分子变为可溶性更高的小分子,故增强了腐殖酸与其他物质之间的相互作用,从而提高了腐殖酸的可絮凝性;光催化改性后的腐殖酸可与Ca²⁺形成Ca-HA结合物,从而进一步降低了腐殖酸含量,最终缓解了腐殖酸对发酵产酸的抑制。本研究结果可为促进污泥发酵产酸、提高污泥有机物转化率提供参考。     

吸附法去除水体中腐殖酸的研究进展

腐殖酸是饮用水消毒副产物的前驱物,成为饮用水微污染的控制对象.介绍了吸附法在去除水体中的腐殖酸的研究应用,阐述了炭质吸附剂、树脂吸附剂和无机矿物质吸附剂去除腐殖酸的研究进展,并展望了复合功能树脂在控制水体微污染中的应用前景.     

pH dependent synthesis and characterization of bismuth molybdate nanostructure for photocatalysis degradation of organic pollutants

Bismuth molybdate (Bi₂MoO₆) nanostructures has attracted many researches as an advanced photocalysts for the organic contaminants. In this paper, bismuth molybdate Bi₂MoO₆ nanoparticles were synthesized using a simple hydrothermal method at varied pH (2, 4, 6, 8, and 10) for 15 h at 180 °C. The results reveal the variation pH precursor solutions have a significant impact on the morphology, phase formations, and photocatalytic activity of samples. The synthesized samples at low pH level were characterized by FESEM analysis revealing Bi₂MoO₆ nanoplates have formed while gradually convert to Bi₂MoO₆ spherical nanoparticle at high PH level as shown in energy dispersive X-ray spectroscopy (DES) peaks. The X-ray diffraction patterns reveal characteristic peaks corresponding to mixed phases of Bi₂MoO₆ and cubic Bi₄MoO₉ at high pH value. The optical absorption study exhibit Bi₂MoO₆ nanoplates absorbed visible light with blue shift when compared to the cubic Bi₄MoO₉ structures. Moreover, the photocatalytic activity results revealed that nanoplates in pH?=?4 sample has excellent photocatalytic activity for degradation of rhodamine (RhB), methylene orange (MO), and phenol under visible-light irradiation (λ?>?400 nm) as well as exhibit the photodegradation 90% of phenol within 300 min.

     

Binding characteristics of Cu2+ to natural humic acid fractions sequentially extracted from the lake sediments

Humic acids (HAs) determine the distribution, toxicity, bioavailability, and ultimate fate of heavy metals in the environment. In this work, ten HA fractions (F1–F10) were used as adsorbent, which were sequentially extracted from natural sediments of Lake Wuliangsuhai, to investigate the binding characteristics of Cu²⁺ to HA. On the basis of the characterization results, differences were found between the ten extracted HA fractions responding to their elemental compositions and acidic functional groups. The characterization results reveal that the responses of ten extracted HA fractions to their elemental compositions and acidic functional groups were different. The O/C and (O + N)/C ratio of F1–F8 approximately ranged from 0.66 to 0.53 and from 0.72 to 0.61, respectively; the measured results showed that the contents of phenolic groups and carboxyl groups decreased from 4.46 to 2.60 mmol/g and 1.60 to 0.58 mmol/g, respectively. The binding characteristics of Cu²⁺ to the ten HA fractions were well modeled by the bi-Langmuir model; the binding behavior of Cu²⁺ to all the ten HA fractions were strongly impacted by pH and ionic strength. The FTIR and SEM-EDX image of HA fractions (pre- and post-adsorption) revealed that carboxyl and phenolic groups were responsible for the Cu²⁺ sorption on the ten sequentially extracted HA fractions process, which is the same with the analysis of the ligand binding and bi-Langmuir models Accordingly, the adsorption capacity of the former HA fractions on Cu²⁺ were higher than the latter ones, which may be attributed to the difference of carboxyl and phenolic group contents between the former and latter extracted HA fractions. Additionally, the functional groups with N and S should not be neglected. This work is hopeful to understand the environmental effect of humic substances, environmental geochemical behavior, and bioavailability of heavy metals in lakes.

     

Assessment of solar driven TiO2-assisted photocatalysis efficiency on amoxicillin degradation

The objective of this work was to evaluate the efficiency of a solar TiO₂-assisted photocatalytic process on amoxicillin (AMX) degradation, an antibiotic widely used in human and veterinary medicine. Firstly, solar photolysis of AMX was compared with solar photocatalysis in a compound parabolic collectors pilot scale photoreactor to assess the amount of accumulated UV energy in the system (Q _UV) necessary to remove 20 mg L^?1 AMX from aqueous solution and mineralize the intermediary by-products. Another experiment was also carried out to accurately follow the antibacterial activity against Escherichia coli DSM 1103 and Staphylococcus aureus DSM 1104 and mineralization of AMX by tracing the contents of dissolved organic carbon (DOC), low molecular weight carboxylate anions, and inorganic anions. Finally, the influence of individual inorganic ions on AMX photocatalytic degradation efficiency and the involvement of some reactive oxygen species were also assessed. Photolysis was shown to be completely ineffective, while only 3.1 kJ_UV?L^?1 was sufficient to fully degrade 20 mg L^?1 AMX and remove 61 % of initial DOC content in the presence of the photocatalyst and sunlight. In the experiment with an initial AMX concentration of 40 mg L^?1, antibacterial activity of the solution was considerably reduced after elimination of AMX to levels below the respective detection limit. After 11.7 kJ_UV?L^?1, DOC decreased by 71 %; 30 % of the AMX nitrogen was converted into ammonium and all sulfur compounds were converted into sulfate. A large percentage of the remaining DOC was in the form of low molecular weight carboxylic acids. Presence of phosphate ions promoted the removal of AMX from solution, while no sizeable effects on the kinetics were found for other inorganic ions. Although the AMX degradation was mainly attributed to hydroxyl radicals, singlet oxygen also plays an important role in AMX self-photosensitization under UV/visible solar light.     

Impacts of horseradish peroxidase immobilization onto functionalized superparamagnetic iron oxide nanoparticles as a biocatalyst for dye degradation

Environmental Science and Pollution Research - To enhance the dye removal efficiency by natural enzyme, horseradish peroxidase (HRP) was immobilized onto amine-functionalized superparamagnetic iron...     

Removal and degradation of aromatic compounds from a highly polluted site by coupling soil washing with photocatalysis

The possible application of two environmental remediation technologies - soil washing and photocatalysis - to remove and decompose various aromatic pollutants present in excavated soils of a contaminated industrial site has been investigated. Aqueous solutions containing the non-ionic surfactant Brij 35 were used to extract the contaminants from the soil samples. The photocatalytic treatment of the obtained washing wastes, performed in the presence of TiO(2) suspensions irradiated with simulated sunlight, showed a slow abatement of the toxic compounds due to the relevant concentrations of organics in the waste. A neat improvement of the process performances, obtained by operating in the presence of added potassium peroxydisulfate, suggests a feasible treatment route.     

Photodecomposition of humic acid and natural organic matter in swamp water using a TiO2-coated ceramic foam filter: Potential for the formation of disinfection byproducts

This paper reports on the photodecomposition of aqueous humic acid (HA) by a TiO₂-coated ceramic foam filter (TCF) reactor and on the potential for the formation of disinfection byproducts (DBPs) upon chlorination of the photocatalytically treated solutions. This photocatalytic reactor can also be applied to the removal of natural organic matter (NOM) in swamp waters. The proposed photocatalytic reaction system was operated as per standardized methodologies. First, the ability of the TCF to decompose HA (a representative compound of NOM) was evaluated from the changes in the total organic carbon (TOC) and UV₂₅₄ with the reaction time. Remarkably, TOC removal and UV₂₅₄ values ranging from 44% to 61% and from 60% to 83%, respectively, were achieved. The potential for the formation of DBPs (total trihalomethane and total haloacetic acid) by chlorination of the phototreated solution was strongly dependent on the TOC removal and UV₂₅₄ values in the solution. The degree of photodecomposition of NOMs in the swamp water samples and the DBP formation potential showed similar trends as in the case of the standard solutions containing HA. The method used in this study could be effectively used to evaluate the efficiency of TCF for reducing HA and NOM, while suppressing the formation of DBP products.     

Kinetics of disaggregation of humic acid in water

The extent of disaggregation of humic acid particles in water was measured as a function of time, initial concentration, pH of the suspension and the temperature. In all experiments the amount of humic acid particles disaggregated was characterized by the corresponding fraction of the suspension, which was able to pass a 0.01 μm membrane filter.It was found that the amount disaggregated after 1000 hours was proportional to the initial concentration of the humic acid particles in the aqueous suspension and increased considerably with the temperature. Decreasing the pH of the suspension from about 6 to zero caused the extent of disaggregation also to decrease continuously.The kinetic measurements revealed that about 3% of the humic acid are disaggregated within 25 hours, 4% within 200 hours and 5% within 1500 hours at a pH around 4. The rates of disaggregation were found to be proportional to the initial concentration of the particles and increased considerably with the temperature.     

Spectroscopic and conformational properties of size-fractions separated from a lignite humic acid

A lignite humic acid (HA) was fractionated by preparative high performance size-exclusion chromatography (HPSEC) in seven different size-fractions. The size-fractions were characterized by cross polarization (CP) magic angle spinning (MAS) (13)C NMR spectroscopy and a further analytical HPSEC elution under UV and fluorescence detection. The alkyl hydrophobic components mainly distributed in the largest molecular-size-fraction, whereas the amount of oxidized carbons increased with decreasing size of fractions. Cross polarization time (T(CH)) and proton spin-lattice relaxation time in the rotating frame (T(1rho)(H)) were measured from variable contact time (VCT) experiments. The bulk HA was characterized by the shortest T(CH) values and the longest T(1rho)(H) values which suggested, respectively, one. an aggregation of components in a large conformation that favored a fast H-C cross polarization, and, two. consequent steric hindrances that prevented fast local molecular motions and decreased proton relaxation rates. Conversely, the separated size-fractions showed longer T(CH) values and shorter T(1rho)(H) values than the bulk HA, thereby indicating that they were constituted by a larger number of mobile molecular conformations. The UV and fluorescence absorptions were both low in the large size-fractions that mainly contained alkyl carbons, whereas they increased in the olephinic- and aromatic-rich fractions with intermediate molecular-size, and decreased again in the smaller fractions which were predominantly composed by oxidized carbons. These results support the supramolecular structure of humic substances and indicate that the observed variation in conformational distribution in humic association may be used to explain environmental processes with additional precision.     

Heterogeneous electro-Fenton process for degradation of bisphenol A using a new graphene/cobalt ferrite hybrid catalyst

Environmental Science and Pollution Research - A simple, efficient, environmentally friendly, and inexpensive synthesis route was developed to obtain a magnetic nano-hybrid (GH) based on graphene...     

Complexation of the antibiotic tetracycline with humic acid

The effect of solution chemistry and sorbate-to-sorbent ratio on the interaction of the antibiotic tetracycline with Elliott soil humic acid (ESHA) was investigated using equilibrium dialysis and FITEQL modeling. Tetracycline speciation strongly influenced its sorption to ESHA. Sorption was strongly pH-dependent with a maximum around pH 4.3, and competition with H+ and electrolyte cation (Na+) was evident. The pH-dependent trend was consistent with complexation between the cationic/zwitterionic tetracycline species and deprotonated sites in ESHA (mainly carboxylic functional groups). Modification of ESHA by Ca2+ addition increased tetracycline sorption suggesting that ternary complex formation (ESHA-metal-tetracycline) may be important at higher concentrations of multivalent metal cations. The macroscopic data (pH-envelope and sorption isotherms) were successfully modeled using a discrete logK function with the FITEQL 4.0 chemical equilibrium program indicating that ESHA-tetracycline interaction could be reasonably represented as complex formation of a monoacid with discrete sites in humic acid. Sorption-desorption hysteresis was observed; both sorption and desorption isotherms were well described by the Freundlich equation.     

去除饮用水中三卤甲烷和腐殖酸的活性炭选型方法

三卤甲烷(THMs)是水中天然有机物在氯化消毒过程中产生的对人体有致癌作用的挥发性有机物,腐殖酸是生成消毒副产物的主要前驱物.活性炭吸附是去除THMs和腐殖酸最常用的方法.不同炭型的活性炭对THMs和腐殖酸的吸附容量并不相同.以饮用水中最常见的THMs(即三氯甲烷)和腐殖酸为吸附对象,进行煤、椰壳和果壳3种不同材质活性炭的吸附容量实验.实验结果验证了苯酚值预测各类活性炭对小分子THMs吸附性能以及丹宁酸值预测各类活性炭对大分子腐殖酸吸附性能的有效性.具有丰富微孔和表面氧化程度较低的上海椰壳炭YK-2和上海果壳专用炭对三氯甲烷的吸附容量比上海原煤破碎高,大孔丰富的上海果壳专用炭和上海原煤破碎对腐殖酸的吸附性能高.将实验结果与美国环保局RREL(Risk Reduction Engineering Laboratory)水污染物处理数据库中相关信息对比发现,相比国外常用活性炭,国产活性炭对三氯甲烷的吸附性能与之相当或略高,具有更好的性价比,应用前景广阔.