催化臭氧化降解含微囊藻毒素污水

应用金属氧化物构建催化臭氧化工艺处理含微囊藻毒素污水,比较了不同催化剂的性能差异,分析了催化剂投加量、温度、pH、原水浓度对该工艺的影响.结果表明,选用CuO作催化剂能较好地处理含微囊藻毒素污水.温度与原水浓度对该工艺影响较小;催化剂投加量与pH是该工艺的主要影响因素.实验温度40℃、混合气体流量1.8 L.L-.1min-1、pH=9、催化剂投加量5 g.L-1、处理时间60 min,原水MC-LR去除率达到90%以上、COD去除率达到64%以上.处理20 min,该工艺催化作用去除MC-LR贡献率达到28%、去除COD贡献率达到52%.     

Fabrication of magnetic multi-template molecularly imprinted polymer composite for the selective and efficient removal of tetracyclines from water

• Magnetic multi-template molecularly imprinted polymer composite was synthesized. • MIP composite was used as the adsorbent for removal of tetracyclines from water. • MIP composite showed excellent adsorption selectivity toward tetracyclines. • MIP composite possessed good reusability. Antibiotic contamination of the water environment has attracted much attention from researchers because of their potential hazards to humans and ecosystems. In this study, a multi-template molecularly imprinted polymer (MIP) modified mesoporous silica coated magnetic graphene oxide (MGO@MS@MIP) was prepared by the surface imprinting method via a sol-gel process and was used for the selective, efficient and simultaneous removal of tetracyclines (TCs), including doxycycline (DC), tetracycline (TC), chlorotetracycline (CTC) and oxytetracycline (OTC) from water. The synthesized MIP composite was characterized by Fourier transform infrared spectroscopy, transmission electron microscope and thermogravimetric analysis. The adsorption properties of MGO@MS@MIP for these TCs were characterized through adsorption kinetics, isotherms and selectivity tests. The MIP composite revealed larger adsorption quantities, excellent selectivity and rapid kinetics for these four tetracyclines. The adsorption process was spontaneous and endothermic and followed the Freundlich isotherm model and the pseudo-second-order kinetic model. The MGO@MS@MIP could specifically recognize DC, TC, CTC and OTC in the presence of some chemical analogs. In addition, the sorption capacity of the MIP composite did not decrease significantly after repeated application for at least five cycles. Thus, the prepared magnetic MIP composite has great potential to contribute to the effective separation and removal of tetracyclines from water.     

磷酸活化活性炭对Cu2+的吸附特征研究

寻求廉价而高效的吸附材料为目的,研究向日葵秸杆基活性炭对铜离子的吸附性能。以向日葵秸秆为原料,经H3PO4活化制备活性炭,通过静态实验研究了其对水溶液中Cu2+的吸附特性,考察了溶液pH值、吸附温度和离子强度对吸附的影响,探讨了吸附热力学、动力学和吸附机理。结果表明:溶液pH值为5～6时活性炭对Cu2+的去除效果最好;向50 mL 170 mg·L-1的溶液中加入0.5 g活性炭,温度为45℃、吸附时间为1 h时,对Cu2+的去除率可达98.3%;Langmuir方程能更好地描述Cu2+在活性炭上的等温吸附特征,静态吸附容量可达41.03 mg·g-1;吸附过程符合拟二级动力学过程,且为吸热的化学吸附过程,膜扩散为速率控制步骤,离子交换可能在吸附过程中起了重要作用。     

Suitability of various chemically prepared activated carbons for the removal of copper(II) ions

Studies on the suitability of various chemically prepared activated carbons (CPACs) like straw carbon (SC), sawdust carbon (SDC), dates nut carbon (DNC) and commercial activated carbon (CAC) for the removal of copper(II) ions by adsorption from simulated wastewater have been carried out under batch mode at 30?±?1°C and the results are compared. The percentage removal of Cu(II) ions increased with a decrease in initial concentration, particle size and added electrolytes (ionic strength) and increased with an increase in contact time, dose of adsorbent and initial pH of the solution. The adsorption data were fitted with the Langmuir isotherm. The applicability of the first order kinetic equation viz. Lagergren equation was tested by correlation analysis. The adsorption process is concluded to be a spontaneous, first order reaction, occurring with increased randomness at the solid–liquid interface. Studies on the desorption of Cu²⁺-loaded activated carbons (ACs) were carried out with nitric acid (0.2–1?N). The possibility of reuse of the regenerated ACs in cycle (in cue-one after another) was tested. SC was found to be a suitable adsorbent alternative to CAC among CPACs for the removal of metal ions, in general, and Cu²⁺ ions, in particular.     

Removal of fluoride by thermally activated carbon prepared from neem (Azadirachta indica) and kikar (Acacia arabica) leaves

The present investigation deals with fluoride removal from aqueous solution by thermally activated neem (Azadirachta indica) leaves carbon (ANC) and thermally activated kikar (Acacia arabica) leaves carbon (AKC) adsorbents. In this study neem leaves carbon and kikar leaves carbon prepared by heating the leaves at 400 degrees C in electric furnace was found to be useful for the removal of fluoride. The adsorbents of 0.3 mm and 1.0 mm sizes of neem and kikar leaves carbon was prepared by standard sieve. Batch experiments done to see the fluoride removal properties from synthetic solution of 5 ppm to study the influence of pH, adsorbent dose and contact time on adsorption efficiency The optimum pH was found to be 6 for both adsorbents. The optimum dose was found to be 0.5g/100 ml forANC (activated neem leaves carbon) and 0.7g/100 ml forAKC (activated kikar leaves carbon). The optimum time was found to be one hour for both the adsorbent. It was also found that adsorbent size of 0.3 mm was more efficient than the 1.0 mm size. The adsorption process obeyed Freundlich adsorption isotherm. The straight line of log (qe-q) vs time at ambient temperature indicated the validity of langergren equation consequently first order nature of the process involved in the present study. Results indicate that besides intraparticle diffusion there maybe other processes controlling the rate which may be operating simultaneously. All optimized conditions were applied for removal of fluoride from four natural water samples.     

BTEX在河流渗滤系统中的降解行为实验模拟研究

河流渗滤是一种自然净化过程,污染河水通过该过程在河流沉积层中发生各种物理、化学和生物作用,使得污染物浓度降低,河水水质得到净化,从而达到增加地下水开采量的目的。本项研究通过淋滤实验,利用自行设计的土柱实验装置和人工配制的淋滤液,模拟了BTEX污染河水在下渗通过河流渗滤系统的过程中发生的降解行为。实验历时48 d,获得了该过程中BTEX各组分和电子受体的质量浓度变化历时曲线,得出的结论包括：污染河水中的BTEX在通过河流渗滤系统时将发生两种环境行为—吸附和降解。其中,吸附作用对于BTEX的净化效果较为有限,当吸附达到饱和之后,在存在电子受体的情况下,BTEX能够发生厌氧微生物降解,降解作用能够更有效的去除BTEX污染物。其中去除效率最高的是间二甲苯,在以NO3-为电子受体的情况下平均去除率为85.5%,在以SO42-为电子受体的情况下平均去除率为82.4%,其次是乙苯、甲苯,去除率最差的是苯,在两种电子受体的系统中平均去除率分别为68.5%和63.5%。由于吸附作用的影响,微生物降解相对于BTEX浓度变化存在一个滞后期,BTEX各组分的土壤-水吸附分配系数Kd越大,总的降解效率也就越低。通过河流渗滤系统这一自然净化过程,可以有效地去除浓度较高的BTEX混合污染,各组分平均去除效率都超过了60%,最高去除率均超过了80%。对于持续不断入渗的污染河水,当土壤吸附达到饱和、微生物活性受到抑制,去除效率会大大降低,从而使BTEX穿透河流沉积层进入含水层,对地下水产生危害。     

Changes in some soil properties at different incubation periods after tobacco waste application

In this study changes in organic carbon (OC), basal soil respiration (BSR), nitrate nitrogen (NO3-N), electrical conductivity (EC) and aggregate stability (AS) of a clay loam soil due to tobacco waste (TOW) application were monitored for 240 days. After incorporating 5% TOW into soil according to oven dry weight basis, soil samples were incubated at field capacity for 20, 40, 80, 140 and 240 days under a greenhouse condition. TOW application significantly increased all soil properties over the control treatment Soil OC and AS values had significant positive correlations each other and with the other soil properties. Soil OC, BSR and AS values significantly increased from 0.12%, 0.03 microg CO2-C g(-1) dry soil 24 hr and 20.7% in control treatment to 1.13%, 3.7 microg CO2-C g(-1) dry soil 24 hr and 54.4% in TOW treatment, respectively in 20 days. While the highest NO3-N (1780 ppm) was found in 40 days, the highest EC (3.35 dS m(-1)) was in 240 days after TOW application. Disaggregation occurred in all treatments after 20 days of incubation due to probably the more substrate demands of microorganisms in soil.     

Adsorption behaviors of activated carbons for the exhaust from spray painting booths in vehicle surface coating

Adsorption performance of activated carbon adsorbers in the downstream duct of vehicle spray painting booths has been studied to understand whether fine paint particles in the off-gas would deteriorate the adsorption capacity of volatile organic compounds (VOCs) on activated carbons. Three forms of activated carbons were selected and their properties were determined using nitrogen adsorption analysis, the measurement of pH value and total ash content, energy dispersion spectrometer, field-emission scanning electron microscopy, and thermogravimetric analysis. Results show that the adsorption capacity of activated carbon strongly depends upon its available specific surface area. When the total uptake on activated carbon approaches saturation, the vapors adsorbed would commence to get displaced by the paint particles gradually as time elapses and finally the uptake of vapors and paint particles reach equilibrium. Microporous carbons, in particular, were much more susceptible to paint particles. A Langmuir-type model for the uptake on activated carbons was suggested, which successfully described the adsorption behaviors of the off-gas released from vehicle spray painting booth.     

微囊藻毒素对束丝藻细胞生长和抗氧化系统的影响

为从活性氧(ROS)角度探讨微囊藻毒素(MC)导致藻类细胞死亡的机理及揭示藻细胞对MC诱发的氧化胁迫的响应机制,采用50和500μg·L-1的微囊藻毒素LR(MC-LR)处理束丝藻(Aphanizomenon sp. DC01)细胞,测定了细胞生长、细胞内活性氧(ROS)含量及抗氧化系统的变化.结果表明,50μg·L-1的MC-LR处理对藻细胞的生长无显著影响,而500μg·L-1的MC-LR处理可诱导藻细胞死亡.50μg·L-1的MC-LR处理的藻细胞ROS含量在处理第2d显著高于对照;但藻细胞能通过还原型谷胱甘肽(GSH)含量,超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GPX)活性改变修复氧化损伤,使ROS水平在处理第3d恢复到对照水平.500μg·L-1的MC-LR处理可显著降低藻细胞GSH含量和SOD与GPX活性,刺激藻细胞生成过量的ROS;ROS在毒素处理4d后突然暴发,过量的ROS引起膜质过氧化,并最终导致藻细胞死亡。     

改性活性炭的表面特性及其对金属离子的吸附性能

本文主要研究了改性对活性炭的表面物理化学特征和对其吸附金属离子性能的影响。研究发现,硝酸氧化可显著增加活性炭表面酸性基团的含量,提高活性炭的表面亲水性,降低pHpzc值,并造成活性炭的结构塌陷和比表面积的减少,因而对活性炭吸附性能产生明显影响,可明显提高对Pb^2 等金属离子的吸附容量。     

Recovery efficiency of the hydrofluorocarbon (HFC‐134a) by activated carbons of different physicochemical properties

The adsorption characteristics of 1,1,1,2‐tetrafluoroethane (HFC‐134a) on activated carbon were investigated to evaluate the recovery efficiency of HFC‐134a by six activated carbons (two granular activated carbons (GAC1 and GAC2), one high‐surface area activated carbon (HAC), and three activated carbon fibers (ACF10, ACF15, and ACF20)). HFC‐134a adsorption on the activated carbons increased with increase in the specific surface area and pore volume of the activated carbon. The differential heat of the HFC‐134a adsorption decreased with increase in the percentage of the micropore volume to the total pore volume. The adsorption model of HFC‐134a on the activated carbon could be based on the Langmuir model. The constant a of the Langmuir plot of HAC and ACF20 is smaller than GAC1 or GAC2 and ACF10 or ACF15, respectively. The constant W_s of HAC has the largest value. The constant a was correlated to the heat of adsorption. It is concluded that the largest amount of HFC‐134a was adsorbed on HAC, and the least amount of interaction occurred between HFC‐134a and the HAC. The amount of HFC‐134a adsorbed on the activated carbons over time was applied to the Sameshima equation. The adsorption rate constant of HFC‐134a on HAC was the largest. The HAC could be suitable for the recovery of HFC‐134a.     

改性活性炭对有机物的吸附性能

研究了表面改性对活性炭吸附各种有机物性能的影响,研究发现,硝酸氧化可显著增加活性炭表面酸性基团的含量,提高了活性炭的表面亲水性,降低pHpzc值,并造成活性炭的结构塌陷和比表面积的减少,因而对活性炭吸附水中的苯酚、苯胺、腐殖酸、氯仿、四氯化碳等有机物的性能产生明显影响,以去除水中有机污染物为目的的活性炭表面改性的方向应为：减少表面内酯基及竣基等含氧官能团的含量,增加活性炭表面的疏水性。     

Removal of chromium(VI) by ZnCl2 activated coir pith carbon

The adsorption of chromium(VI) onto ZnCl₂ activated carbon developed from coir pith was investigated to assess the possible use of this adsorbent. The influence of contact time, adsorbent dose, Cr(VI) concentration, pH and temperature were investigated. The two theoretical adsorption isotherms, namely, Langmuir and Freundlich were used to describe the experimental results. The Langmuir adsorption capacity (Q ₀) was found to be 120.5?mg Cr(VI) per g of the adsorbent. The adsorption followed the second-order kinetics and was found to be maximum at pH 2.0. The pH effect and the desorption studies showed that ion exchange mechanism might be involved in the adsorption process. The effects of foreign ions such as chloride, sulphate, phosphate, selenite, molybdate, nitrate and perchlorate on the removal of Cr(VI) have been investigated. The removal of Cr(VI) from synthetic ground water was also tested. The results show that ZnCl₂ activated coir pith carbon is effective for the removal of Cr(VI) from water.     

Microcystin-LR biodegradation by Sphingopyxis sp. USTB-05

A promising bacterial strain for biodegrading microcystin-LR (MC-LR) as the sole carbon and nitrogen source was successfully isolated from Lake Dianchi, China. The strain was identified as Sphingopyxis sp. USTB-05, which was the first isolated MCs-biodegrading Sphingopyxis sp. in China. The average biodegradation rate of MC-LR by Sphingopyxis sp. USTB-05 was 28.8 mg??L^?1 per day, which was apparently higher than those of other bacteria reported so far. The optimal temperature and pH for both strain USTB-05 growth and MC-LR biodegradation were 30??C and 7.0, respectively. The release of MC-LR from the cyanobacterial cells collected from Lake Guishui and the biodegradation of MC-LR by both strain and cell-free extract (CE) were investigated. The results indicated that MC-LR with the initial concentration of 4.0 mg??L^?1 in water was biodegraded by Sphingopyxis sp. USTB-05 within 4 d, while MC-LR with the initial concentration of 28.8 mg??L^?1 could be completely removed in 3 h by CE of Sphingopyxis sp. USTB-05 containing 350 mg??L^?1 protein. During enzymatic biodegradation of MC-LR, two intermediate metabolites and a dead-end product were observed on an HPLC chromatogram. Moreover, the similar scanning profiles of MC-LR and its metabolic products indicate that the Adda side-chain of MC-LR was kept intact in all products.     

Solid substrate fermentation of cassava fibrous residue for production of alpha-amylase, lactic acid and ethanol

There is serious concern about the disposal of solid residues left after large scale extraction of starch from cassava. Owing to the high starch content (55-65% on dry weight basis) and organic matter of these wastes, an attempt has been made to utilize it for the production of three bioproducts, i.e. alpha-amylase, lactic acid and ethanol in solid substrate fermentation by incubating the solid residue at different moisture holding capacity (40-80%) and incubation period (12- 60 hr for alpha-amylase, 24-144 hr for ethanol and 2-10 days for lactic acid). The highest product yield was obtained at 60% moisture holding capacity of the residue and period of incubation varied from 36 hr (alpha-amylase), 120 hr (ethanol) to 6 days (lactic acid). This study showed that the solid residues from cassava starch factories could serve as a low-cost substrate for bioproducts production.     

磷酸活化活性炭对Cu~（2＋）的吸附特征研究

寻求廉价而高效的吸附材料为目的,研究向日葵秸杆基活性炭对铜离子的吸附性能。以向日葵秸秆为原料,经H3PO4活化制备活性炭,通过静态实验研究了其对水溶液中Cu2＋的吸附特性,考察了溶液pH值、吸附温度和离子强度对吸附的影响,探讨了吸附热力学、动力学和吸附机理。结果表明：溶液pH值为5～6时活性炭对Cu2＋的去除效果最好;向50 mL 170 mg·L-1的溶液中加入0.5 g活性炭,温度为45℃、吸附时间为1 h时,对Cu2＋的去除率可达98.3%;Langmuir方程能更好地描述Cu2＋在活性炭上的等温吸附特征,静态吸附容量可达41.03 mg·g-1;吸附过程符合拟二级动力学过程,且为吸热的化学吸附过程,膜扩散为速率控制步骤,离子交换可能在吸附过程中起了重要作用。     

Catalytic ozonation of organic compounds in water over the catalyst of RuO2/ZrO2-CeO2

This research investigates the performances of RuO₂/ZrO₂-CeO₂ in catalytic ozonation for water treatment. The results show that RuO₂/ZrO₂-CeO₂ was active for the catalytic ozonation of oxalic acid and possessed higher stability than RuO₂/Al₂O₃ and Ru/AC. In the catalytic ozonation of dimethyl phthalate (DMP), RuO₂/ZrO₂-CeO₂ did not enhance the DMP degradation rate but significantly improved the total organic carbon (TOC) removal rate. The TOC removal in catalytic ozonation was 56% more than that in noncatalytic ozonation. However this does not mean the catalyst was very active because the contribution of catalysis to the overall TOC removal was only 30%. The adsorption of the intermediates on RuO₂/ZrO₂-CeO₂ played an important role on the overall TOC removal while the adsorption of DMP on it was negligible. This adsorption difference was due to their different ozonation rates. In the catalytic ozonation of disinfection byproduct precursors with RuO₂/ZrO₂-CeO₂, the reductions of the haloacetic acid and trihalomethane formation potentials (HAAFPs and THMFPs) for the natural water samples were 38%–57% and 50%–64%, respectively. The catalyst significantly promoted the reduction of HAAFPs but insignificantly improved the reduction of THMFPs as ozone reacts fast with the THMs precursors. These results illustrate the good promise of RuO₂/ZrO₂-CeO₂ in catalytic ozonation for water treatment.     

Application of magnesite–bentonite clay composite as an alternative technology for removal of arsenic from industrial effluents

This study evaluated the feasibility of integrating amorphous magnesite and bentonite clay (composite) as an alternative technology for removing arsenic from industrial effluents. The removal of arsenic from industrial effluents by using magnesite–bentonite clay composite was carried out in batch mode. The effects of equilibration time, adsorbent dosage, adsorbate concentration, and pH on removal of arsenic were investigated. The experiments demonstrated that ≈100% arsenic removal is optimum at 30 minutes of agitation, 2 g of adsorbent dosage (2 g: 100 mL, S/L ratio), and 20 mg L^?1 of arsenic concentration. The adsorption data fitted well to both Langmuir and Freundlich adsorption models, hence proving monolayer and multilayer adsorption. The kinetic studies revealed that the data fitted better to a pseudo-second-order reaction than to a pseudo-first-order reaction, hence proving chemisorption. At optimized conditions, the composite was able to remove arsenic to below World Health Organization water quality guidelines, hence depicting that the composite is effective and efficient in removing arsenic from contaminated water. Based on that, this comparative study proves that the composite is a promising adsorbent with high adsorption capacity for arsenic and can be a suitable substitute for the conventional treatment methods.     

Oxidation and biotoxicity assessment of microcystin-LR using different AOPs based on UV,O3 and H2O2

MC-LR removal performances under different AOPs were compared systematically. Higher removal efficiency and synergistic effects were obtained by combined process. The acute biotoxicity raised in different degrees after oxidation. Microcystin-LR attracts attention due to its high toxicity, high concentration and high frequency. The removal characteristics of UV/H₂O₂ and O₃/H₂O₂ advanced oxidation processes and their individual process for MC-LR were investigated and compared in this study. Both the removal efficiencies and rates of MC-LR as well as the biotoxicity of degradation products was analyzed. Results showed that the UV/H₂O₂ process and O₃/H₂O₂ were effective methods to remove MC-LR from water, and they two performed better than UV-, O₃-, H₂O₂-alone processes under the same conditions. The effects of UV intensity, H₂O₂ concentration and O₃ concentration on the removal performance were explored. The synergistic effects between UV and H₂O₂, O₃ and H₂O₂ were observed. UV dosage of 1800 mJ·cm⁻² was required to remove 90% of 100 mg·L⁻¹ MC-LR, which amount significantly decreased to 500 mJ·cm⁻² when 1.7 mg·L⁻¹ H₂O₂ was added. 0.25 mg·L⁻¹ O₃, or 0.125 mg·L⁻¹ O₃ with 1.7 mg·L⁻¹ H₂O₂ was needed to reach 90% removal efficiency. Furthermore, the biotoxicity results about these UV/H₂O₂, O₃/H₂O₂ and O₃-alone processes all present rising trends with oxidation degree of MC-LR. Biotoxicity of solution, equivalent to 0.01 mg·L⁻¹ Zn²⁺, raised to 0.05 mg·L⁻¹ Zn²⁺ after UV/H₂O₂ or O₃/H₂O₂ reaction. This phenomenon may be attributed to the aldehydes and ketones with small molecular weight generated during reaction. Advice about the selection of MC-LR removal methods in real cases was provided.     

Assesment of disinfection by‐products removal by ozonation coupled with adsorption

This research work was performed to evaluate ozonation and granular activated carbon adsorption processes from the view‐point of controlling the formation of disinfection by products (DBPs). Both the humic acid and raw water were first preozonated and then adsorbed on the activated carbon to assess the potency for removal of total organic carbon (TOC) and DBPs. The disinfection by‐product including THMs and HAAs, in principle, can be successfully removed through a use of the ozonation and granular activated carbon (GAC) adsorption processes. However, in practice dealing with the raw water, it is necessary to introduce the pilot‐plant to obtain the design and operation guidelines for the water treatment plant through the ICA (Instrumentation Control and Automation) program in our future research work.