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1.
Comparative study of Cu-based bimetallic oxides for Fenton-like degradation of organic pollutants.
Wang, Q, Ma, Y, Xing, S
Chemosphere. 2018;:450-456
Abstract
In order to provide useful information for the rational design of effective Fenton-like catalyst, a series of Cu-based bimetallic oxides were synthesized and their Fenton-like performances for the degradation of Orange II and ciprofloxacin were compared. The structure, chemical oxidation state, surface charge property and redox ability of the catalysts were also investigated by different characterization techniques. Among them, NiCu exhibited the highest adsorption capacity towards Orange II and the highest activity for the production of OH from H2O2 decomposition, which could be attributed to its high surface area and highly positively charged surface. However, FeCu exhibited the highest activity for the degradation of Orange II. The reason might be that FeCu has more unpaired electrons and higher redox ability, thus promoting the activation of adsorbed Orange II through the electron transfer process. By contrast, NiCu exhibited the highest activity for the removal of ciprofloxacin because ciprofloxacin was mainly degraded by OH. Finally, the main degradation intermediates of Orange II and ciprofloxacin were determined by liquid chromatography-mass spectrometry.
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Comparative evaluation of cyanide removal by adsorption, biodegradation, and simultaneous adsorption and biodegradation (SAB) process using Bacillus cereus and almond shell.
Dwivedi, N, Balomajumder, C, Mondal, P
Journal of environmental biology. 2016;(4):551-6
Abstract
The present study aimed to investigate the removal efficiency of cyanide from contaminated water by adsorption, biodegradation and simultaneous adsorption and biodegradation (SAB) process individually in a batch reactor. Adsorption was achieved by using almond shell granules and biodegradation was conducted with suspended cultures of Bacillus cereus, whereas SAB process was carried out using Bacillus cereus and almond shell in a batch reactor. The effect of agitation time, pH, and initial cyanide concentration on the % removal of cyanide has been discussed. Under experimental conditions, optimum removal was obtained at pH 7 with agitation time of 48 hrs and temperature of 35 degrees C. Cyanide was utilized by bacteria as sole source of nitrogen for growth. The removal efficiencies of cyanide by adsorption, biodegradation, and SAB were found to be 91.38%, 95.87%, and 99.63%, respectively, at initial cyanide concentration of 100 mg l(-1). The removal efficiency of SAB was found to be better as compared to that of biodegradation and adsorption alone.
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3.
Comparison of denitrification performances using PLA/starch with different mass ratios as carbon source.
Wu, C, Tang, D, Wang, Q, Wang, J, Liu, J, Guo, Y, Liu, S
Water science and technology : a journal of the International Association on Water Pollution Research. 2015;(7):1019-25
Abstract
A suitable carbon source is significant for biological nitrate removal from groundwater. In this study, slow-release carbon sources containing polylactic acid (PLA) and starch at 8:2, 7:3, 6:4, 5:5, 4:6, and 3:7 ratios were prepared using a blending and fusing technique. The PLA/starch blend was then used as a solid carbon source for biological nitrate removal. The carbon release rate of PLA/starch was found to increase with increased starch content in leaching experiments. PLA/starch at 5:5 mass ratio was found to have the highest denitrification performance and organic carbon consumption efficiency in semi-continuous denitrification experiments, and was also revealed to support complete denitrification at 50 mg-N/L influent nitrate concentration in continuous experiments. The effluent nitrate concentration was <2 mg NO(3)(-)-N/L, which met the national standard (GB 14848-93) for groundwater. Scanning electron microscopy results further showed that the surface roughness of PLA/starch increased with prolonged experimental time, which may be conducive to microorganism attachment. Therefore, PLA/starch was a suitable carbon source and biofilm carrier for groundwater remediation.
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4.
Study and comparison of polydopamine and its derived carbon decorated nanoparticles in the magnetic solid-phase extraction of estrogens.
Huang, Z, Lee, HK
Journal of chromatography. A. 2015;:41-50
Abstract
Surface functionalization enabled by bioinspired polydopamine (PDA) is recognized as a convenient route for fabrication of multifunctional nanoparticles. In the present work, magnetic nanoparticles with polymer (Fe3O4@PDA) and carbon shell (Fe3O4@C) were prepared by self-oxidation of dopamine, and carbonization of the PDA coating. The performance of the two magnetic sorbents in the extraction and determination of four estrogens, estrone (E1), estradiol (E2), estriol (E3) and diethylstilbestrol (DES) from water samples in the form of magnetic solid-phase extraction was investigated. Orthogonal array design was utilized to facilitate the optimization of the proposed sample preparation approach. The highest extraction capabilities of the two sorbents were achieved under different experimental conditions. Fe3O4@PDA was shown to be superior to Fe3O4@C in the enrichment of estrogens, suggesting stronger interactions were established between the PDA coating and the target compounds. The extraction and desorption operations were enabled more conveniently by magnetic separation and the extracts were analyzed by high-performance liquid chromatography coupled with ultraviolet and fluorescence detection. The limits of detection achieved in the proposed method were in the range of 0.072-0.15ng/mL for E1 and DES, and 0.0017-0.0062ng/mL for E2 and E3. Good precision (>0.9995) was obtained with the linearity ranging from 0.2 to 100ng/mL, and from 0.01 to 5ng/mL. The method developed was assessed by analysis of the estrogens in tap water, drain water and bottled mineral water samples.
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5.
Treatment of wastewater using a sequencing batch reactor.
de Sousa, JT, Miná, VG, Lopes, WS, Leite, VD, de Oliveira, MF
Environmental technology. 2013;(5-8):1035-42
Abstract
The aim of this study was to evaluate the efficiency of two sequencing batch reactors (R1 and R2) at removing nutrient (N and P) and chemical oxygen demand (COD). The two reactors (R1 and R2) were of the same design, operating under identical cycles and had a sludge retention time of 5 d. In R1, the substrate was sewage enriched with cooked and triturated cereals. In R2, the substrate was raw sewage mixed with triturated discarded excess sludge. Respirometry tests were performed to compare the biodegradability of the substrates used during the experimental period. The efficiency of R1 in removing soluble P and N-ammonia was considerably higher (90.4 and 97.2%, respectively) than reactor R2 (60 and 39.2%, respectively). While the effluent generated by R1 contained only minor amounts of N-nitrite and N-nitrate (0.5 +/- 0.4 and 1.7 +/- 0.8 mg L(-1), respectively). The concentrations of nitrite and nitrate in the effluent from R2 were 2 and 7 times higher. The lack of biodegradable COD available for denitrification was responsible for the high concentrations of nitrite and nitrate in the effluent of R2.
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6.
Comparative study of chromium biosorption by Mesorhizobium amorphae strain CCNWGS0123 in single and binary mixtures.
Xie, P, Hao, X, Mohamad, OA, Liang, J, Wei, G
Applied biochemistry and biotechnology. 2013;(2):570-87
Abstract
The appearance of chromium in the aqueous effluent is a major concern for the modern industry. In this work, Mesorhizobium amorphae strain CCNWGS0123 was investigated as a biosorbent to remove chromium from aqueous solutions. The optimum pH for Cr(III) and Cr(VI) biosorption were 4 and 2, respectively. This isolate showed an experimental maximum Cr(III) adsorption capacity of 53.52 mg L(-1), while the result was 47.67 mg L(-1) for Cr(VI), with an initial 100 mg L(-1) Cr ions and 1.0 g L(-1) biomass. In terms of time equilibrium, Cr(III) ion was more readily adsorbed than Cr(VI) by this isolate. The biosorption data of both ions fit the Langmuir isotherm better than that of Freundlich model. Meanwhile, this organism exhibited a good capability to release Cr ions, with desorption efficiency of 70 % for Cr(III) and 76 % for Cr(VI). Fourier transform infrared spectroscopy analysis showed that -OH, -COO, -NH, amide I, and C=O were involved in Cr(III) and Cr(VI) binding. The biosorbent was further characterized by scanning electron microscopy and energy-dispersive X-ray spectrometry, which indicated an accumulation of chromium on the cellular level. In the binary mixtures, the removal ratio of total Cr and Cr(III) increased from pH 2 to 4. The highest removal ratio of the total Cr was observed in the 25/25 mg L(-1) mixture at pH 4. In addition, the removal efficiency of Cr(VI) was closely influenced by Cr(III) in the mixture, decreasing to 23.57 mg g(-1) in the 100/100 mg L(-1) mixture system, due to the competition of Cr(III). The potential usage of the chromium-resistant rhizobium for the remediation of chromium-contaminated effluents has been demonstrated based on the above results.
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7.
Characterizing the discoloration of methylene blue in Fe0/H2O systems.
Noubactep, C
Journal of hazardous materials. 2009;(1):79-87
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Abstract
Methylene blue (MB) was used as a model molecule to characterize the aqueous reactivity of metallic iron in Fe(0)/H(2)O systems. Likely discoloration mechanisms under used experimental conditions are: (i) adsorption onto Fe(0) and Fe(0) corrosion products (CP), (ii) co-precipitation with in situ generated iron CP, (iii) reduction to colorless leukomethylene blue (LMB). MB mineralization (oxidation to CO(2)) is not expected. The kinetics of MB discoloration by Fe(0), Fe(2)O(3), Fe(3)O(4), MnO(2), and granular activated carbon were investigated in assay tubes under mechanically non-disturbed conditions. The evolution of MB discoloration was monitored spectrophotometrically. The effect of availability of CP, Fe(0) source, shaking rate, initial pH value, and chemical properties of the solution were studied. The results present evidence supporting co-precipitation of MB with in situ generated iron CP as main discoloration mechanism. Under high shaking intensities (>150 min(-1)), increased CP generation yields a brownish solution which disturbed MB determination, showing that a too high shear stress induced the suspension of in situ generated corrosion products. The present study clearly demonstrates that comparing results from various sources is difficult even when the results are achieved under seemingly similar conditions. The appeal for an unified experimental procedure for the investigation of processes in Fe(0)/H(2)O systems is reiterated.
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8.
Hybrid anion exchanger for trace phosphate removal from water and wastewater.
Blaney, LM, Cinar, S, SenGupta, AK
Water research. 2007;(7):1603-13
Abstract
Throughout recent decades, the wastewater treatment industry has identified the discharge of nutrients, including phosphates and nitrates, into waterways as a risk to natural environments due to the serious effects of eutrophication. For this reason, new tertiary treatment processes have abounded; these processes generally utilize physico-chemical and biological methods to remove nutrients from secondary wastewaters. The disadvantages of such methods involve larger reactor volumes, operating costs, and waste sludge production; furthermore, complete nutrient removal is unattainable due to thermodynamic and kinetic limitations. The subject study presents the development and performance of a new phosphate-selective sorbent, referred to as hybrid anion exchanger or HAIX. HAIX combines durability and mechanical strength of polymeric anion exchange resins with high sorption affinity of hydrated ferric oxide (HFO) toward phosphate. HAIX is essentially a polymeric anion exchanger within which HFO nanoparticles have been dispersed irreversibly. Laboratory studies show that HAIX selectively removes phosphate from the background of much higher concentrations of competing sulfate, chloride and bicarbonate anions due to the combined presence of Coulombic and Lewis acid-base interactions. Experimental results demonstrate that HAIX's phosphate-sulfate separation factor is over two orders of magnitude greater than that of currently available commercial ion exchange resins. Additionally, optimal HAIX performance occurs at typical secondary wastewater pH conditions i.e., around 7.5. HAIX is amenable to efficient regeneration and reuse with no noticeable loss in capacity.
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9.
Modified Fenton reaction for trichlorophenol dechlorination by enzymatically generated H2O2 and gluconic acid chelate.
Ahuja, DK, Bachas, LG, Bhattacharyya, D
Chemosphere. 2007;(11):2193-200
Abstract
Glucose oxidase is a well-known enzyme that catalyzes the oxidation of beta-D-glucose to produce gluconic acid and hydrogen peroxide. Fenton reaction is a powerful oxidation technology used for the oxidation of groundwater pollutants. For the application of Fenton reaction in groundwater remediation, successful operation of Fenton reaction near neutral pH, and on-site generation of both H2O2 and chelate will be beneficial. The focus of this experimental study was to couple the glucose oxidation reaction with chelate-based Fenton reaction. The idea was to use the hydrogen peroxide and chelate gluconic acid generated during glucose oxidation for the dechlorination of 2,4,6-trichlorophenol (TCP) by Fenton reaction. The oxidation of glucose was achieved using the enzyme in free and immobilized forms. The rate of production of hydrogen peroxide was determined for each system, and was used to estimate the time required for complete consumption of glucose during the process, thus avoiding any traces of glucose in the Fenton reaction. In the case of free enzyme reaction, separation of the enzyme was achieved using an ultrafiltration membrane before initiating the Fenton reaction. The oxidation of TCP by Fenton reaction was performed at varying ratios of gluconic acid/Fe, and its effect on the decomposition of TCP and H2O2 was studied. TCP degradation was studied both in terms of parent compound degradation and free chloride generation.
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10.
Comparison of zinc complexation properties of dissolved natural organic matter from different surface waters.
Cheng, T, Allen, HE
Journal of environmental management. 2006;(3):222-9
Abstract
The zinc binding characteristics of natural organic matter (NOM) from several representative surface waters were studied and compared. NOM samples were concentrated by reverse osmosis. The samples were treated in the laboratory to remove trace metals. Square wave anodic stripping voltammetry (SWASV) was used to study zinc complexing properties of those NOM samples at fixed pH, ionic strength, and dissolved organic carbon (DOC) concentrations. Experimental data were compared to the predictions from the Windermere Humic Aqueous Model (WHAM) Version VI. At the same pH, ionic strength, and temperature, the zinc titration curves for NOM samples from different surface water sources tested in our study almost overlapped each other, indicating similarity in zinc binding properties of the NOM. A discrete two-site model gave good fits to our experimental titration data. Non-linear fitting by FITEQL 4.0 shows that the conditional zinc binding constants at the same pH are similar for NOM from different sources, indicating that zinc complexation characteristics of the NOM used in our study do not depend on their origin and one set of binding parameters can be used to represent Zn-NOM complexation for NOM samples from those different surface water sources representing geographically diverse locations. In addition, the total ligand concentrations (L(1,T), L(2,T), and L(T)) of all NOM show no observable gradation with increasing pH (L(1,T)=2.06+/-0.80 mmol/g carbon; L(2,T)=0.12+/-0.04 mmol/g carbon; L(T)=2.18+/-0.78 mmol/g carbon), while the conditional binding constants of zinc by NOM (logK(ZnL)(c)) show a linear increase with increasing pH(logK(1)(c)(pH=6.0)=4.69+/-0.25; logK(1)(c)(pH=7.0)=4.94+/-0.10; logK(1)(c)(pH=8.0)=5.25+/-0.006; logK(2)(c)(pH=6.0)=6.29+/-0.13; logK(2)(c)(pH=7.0)=6.55+/-0.08; logK(2)(c)(pH=8.0)=6.86+/-0.023) with a slope of ca. 0.28, indicating the zinc-NOM complexes become more stable at higher pH. The WHAM VI predicted free zinc ion activities at high zinc concentrations agree with our experimental results at pH 6.0, 7.0, and 8.0. However, the zinc binding of these NOM samples is over estimated by WHAM VI at zinc concentrations below 10(-6) M at pH 8.0.