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1.
In the present investigation, treatment of metal cutting wastewater (MCW) using electrocoagulation (EC) process is designed and analyzed using response surface methodology (RSM). RSM is applied to optimize the operating variables viz. initial pH, current density, and operating time on the treatment of MCW in a batch mode by EC process using iron and aluminum electrodes. Quadratic models are developed for the responses such as chemical oxygen demand (COD), total organic carbon (TOC), and turbidity, and operating cost is calculated with respect to energy, electrode, and chemical consumptions. The actual COD, TOC, and turbidity removal efficiencies at optimized conditions are found to be 93.0%, 83.0%, and 99.8% for Fe electrode and 93.5%, 85.2%, and 99.9% for Al electrode, respectively, which agree well with the predicted response. The proposed model fits very well with the experimental data with R 2 adjusted correlation coefficients of 0.927 for COD, 0.924 for TOC, and 0.968 for turbidity removal for Al and 0.904 for COD, 0.976 for TOC, and 0.989 for turbidity removal for Fe electrodes, respectively. This study clearly shows that RSM is one of the suitable methods to optimize the operating conditions and maximize the COD, TOC, and turbidity removal efficiencies for both electrodes while keeping the operating costs to minimal (0.371 ?/m3 for Fe and 0.337 ?/m3 for Al electrodes).  相似文献   

2.
The application of magnetite-immobilized chitin in pentachlorophenol (PCP) removal was demonstrated in this study. The physicochemical parameters for immobilization of chitin by magnetite, and for PCP adsorption using magnetite-immobilized chitin were optimized. For chitin immobilization, the optimized conditions were: magnetite to chitin (m:c) ratio at 1:2, initial pH 6, 25°C, 200 rpm and 60 min in batch system. The immobilization efficiency (IE) was 99.4% and immobilization capacity (IC) was 2.0 mg chitin mg?1 magnetite. High initial pH (pH?>?11) and temperature (>30°C) lowered the IE and IC. For PCP (10 mg l?1) adsorption, the optimized conditions were: 1,500 mg l?1 immobilized chitin, initial pH 6, 25°C, 200 rpm and 60 min in batch system. The removal efficiency (RE) was 57.9% and removal capacity (RC) was 5.4 mg g?1. The adsorption ability of immobilized chitin decreased with pH and temperature increased. However, increasing the amount of immobilized chitin (24,000 mg l?1) can increase the RE up to 92%. Both chitin immobilization and PCP adsorption exhibited Langmuir and Freundlich adsorption isotherms. Results in this study indicated that magnetite-immobilized chitin was a cost-effective and environmental friendly adsorbent to remove environmental pollutants such as PCP.  相似文献   

3.
The photo-Fenton oxidation treatment combined with a coagulation/flocculation process was investigated for removal of chemical oxygen demand (COD) from a refractory petroleum refinery wastewater. Scrap iron shavings were used as the catalyst source. A response surface methodology (RSM) with a cubic IV optimal design was employed for optimizing the treatment process. Kinetic studies showed that the proposed process could be described by a two-stage, second-order reaction model. Experiments showed that precipitation of iron ions can be utilized as a post-oxidation coagulation stage to improve the overall treatment efficiency. More than 96.9% of the COD removal was achieved under optimal conditions, with a post-oxidation coagulation stage accounting for about 30% of the removal, thus confirming the collaborative role of oxidation and coagulation in the overall treatment. A low-velocity gradient of 8.0 s?1 for a short mixing time of 10 min resulted in optimum post-oxidation coagulation. Comparison of photo-Fenton oxidation to a standard Fenton reaction in the same wastewater showed more rapid COD removal for photo-Fenton, with an initial second-order rate constant of 4.0 × 10?4 L mg?1 min?1 compared to the Fenton reaction’s overall second-order rate constant of 7.0 × 10?5 L mg?1 min?1.  相似文献   

4.
In this work, the effects of various operating parameters (pressure, pH, BPA concentration, and filtration time) toward bisphenol A (BPA) removal via ultrafiltration (UF) membrane system were investigated using response surface methodology (RSM). Historical data design of RSM was used to obtain the interaction between variables and response as well as optimizing the process. The analysis of variance (ANOVA) showed that the third-order polynomial model was significant in which pH and filtration time were identified as significant terms that influence BPA removal. The 3D response surface plots revealed the two-factor interaction between independent and dependent variables. The optimization process of the model predicted optimum conditions of 99.61% BPA removal at 1 bar, pH 6.7, 10 μg/L BPA concentration, and 10-min filtration time. The predicted optimum conditions for BPA removal were consistent with the obtained experimental values, indicating reliable application of historical data design RSM for modeling BPA removal in UF membrane system.  相似文献   

5.
In this paper, Taguchi method was applied to determine the optimum condition for Pb (II) removal from aqueous solution by spent Agaricus bisporus. An orthogonal array experiment design (L9(34) which is of four control factors (pH, t (contact time), m (sorbent mass), and C 0 (initial Pb (II) concentration)) having three levels was employed. Biosorption capacity (mg metal/g biosorbent) and percent removal (%) were investigated as the quality characteristics to be optimized. In order to determine the optimum levels of the control factors precisely, range analysis and analysis of variance were performed. The optimum condition for biosorption capacity was found to be pH?=?5.00, t?=?5.0 h, m?=?0.010 g, and C 0?=?50 mg/L. And for percent removal, the optimum condition was found to be pH?=?4.00, t?=?4.0 h, m?=?0.100 g, and C 0?=?50 mg/L. Under these optimum conditions, biosorption capacity and percent removal can reach 60.76 mg/g and 80.50%, respectively.  相似文献   

6.
The present study was carried out in order to investigate the removal of soluble Mn2+ from an aqueous solution using Bacillus cereus. A manganese aqueous solution at 50 mg L?1 was treated, and the product was less than 1 mg L?1 of residual concentration, which complied with environmental regulations. Before the optimization, B. cereus was able to remove Mn2+ ions from an aqueous solution; however, the residual content was around 2.5 mg L?1. Screening experiments aiming at defining the effects of the growth medium composition indicated that both casamino acid-peptone and yeast extract contributed to manganese removal. These experiments also showed the interaction between these two components of the culture media, nevertheless the use of glucose did not prove significant. Considering these observations, the Doehlert design was used to generate a response surface. The model was significant with the p value lower than 0.05 and the lack-of-fit not significant (p > 0.05). The optimized composition of the growth medium was defined as 0.5 g L?1 of casamino acid-peptone and 0.25 g L?1 of yeast extract, whereas glucose could be removed from the original growth medium. When the optimized condition of the growth medium was used, the time required for manganese removal was reduced from 21 to 8 days. After optimization, B. cereus was capable of producing high manganese removal, reducing the residual concentration to levels below 1.0 mg L?1.  相似文献   

7.
An organophilic calcined hydrotalcite (OHTC) was prepared by treating calcined hydrotalcite (HTC) with sodium dodecylbenzene sulphonate (an anionic surfactant) to achieve a high loading of thiol functionality through the immobilization of 2-mercaptobenzimidazole (MBI) as a chelating agent. The adsorbent (MBI-OHTC) obtained was characterized using XRD, FTIR, SEM, TG/DTG, surface area analysis and potentiometric titration. The adsorption of MBI-OHTC to remove Hg(II) ions from aqueous solutions was studied as a function of pH, contact time, metal ion concentration, ionic strength and adsorbent dose. The optimum pH range for the maximum removal of Hg(II) was 6.0–8.0. The maximum value of Hg(II) adsorption was found to be 11.63 and 21.52 mg g?1 for an initial concentration of 25 and 50 mg l?1, respectively at pH 8.0. The equilibrium conditions were achieved within 3 h under the mixing conditions employed. A reversible pseudo-first-order used to test the adsorption kinetics. The adsorption mechanism consisted of external diffusion and intraparticle diffusion and the intraparticle mass transfer diffusion was predominated after 20 min of experiment. Extent of adsorption decreased with increase of ionic strength. The experimental isotherm was analyzed with two parameters (Langmuir and Freundlich) and three parameters (Redlich–Peterson) equations. The isotherm data were best modeled by the Freundlich isotherm equation. Complete removal (≈100%) of Hg(II) from 1.0 l of chlor-alkali industry wastewater containing 9.86 mg Hg(II) ions, was possible with 3 g of the adsorbent dose at pH 8.0. About 95.0% of Hg(II) can be recovered from the spent adsorbent using 0.1 M HCl.  相似文献   

8.
In the present study, the immobilizing fermentation characteristics and o-chlorophenol biodegradation of Rhodopseudomonas palustris using mycelial pellets as a biomass carrier were investigated. To improve the o-chlorophenol degradation efficiency of the combined mycelial pellets, eight cultivation variables including glucose concentration, yeast extract concentration, spore inoculum size, pH, and agitation speed were optimized with an integrated strategy involving a combination of statistical designs. First, Plackett-Burman experiments identified glucose, yeast extract, and spore inoculum size as three statistically significant factors important for o-chlorophenol removal. Then, the steepest ascent method was used to access the optimal region of these significant factors. Finally, response surface methodology by Box-Behnken optimization was used to examine the mutual interactions among these three variables to determine their optimal levels. The ideal culture conditions for maximum o-chlorophenol removal according to a second-order polynomial model were as follows: 15.60 g/L glucose, 3.09 g/L yeast extract, and 9% (v/v) spore inoculum size, resulting in an expected o-chlorophenol removal rate of 92.60% with an o-chlorophenol initial concentration of 50 mg/L and 96-h culture time. The correlation coefficient (R 2 = 0.9933) indicated excellent agreement between the experimental and predicted values, whereas a fair association was observed between the predicted model values and those obtained from subsequent experimentation at the optimized conditions.  相似文献   

9.
The objective of this work was to optimize the synthetic dairy effluent (SDE) treatment using the central composite rotatable design (CCRD) and the Doehlert matrix to evaluate the adjustment of the models to the data, besides verifying if it is possible to find the same optimum point to the turbidity removal, chemical oxygen demand (COD), and UV254 compounds using two experimental designs. The coagulation and flocculation assays were made in jar test and the flotation in a flotatest in bench scale. For each experimental design, the effect of two organic coagulants was evaluated in the removal of turbidity, COD, and UV254 compounds of the SDE: the polyacrylamide (PAM) and the Tanfloc. The generated mathematical models in both experimental designs adjusted well to the data, showing a high capacity of prediction. To the PAM coagulant, the optimal point found in the CCRD design was 46.49 mg L?1 of coagulant in a pH of 6.53; in the Doehlert design, the optimal point in the CCRD was 48.40 mg L?1 of coagulant in a pH of 6.50. When Tanfloc was used, in the CCRD, the optimal point found was 40.42 mg L?1 of coagulant in a pH of 5.00 and, in Doehlert design, the optimum found was 37.57 mg L?1 in a pH of 5.05. It is concluded that, using a smaller number of runs, through Doehlert design is possible to find the optimal point really close to the obtained through CCRD in which are observed efficiencies of similar pollutant removal.  相似文献   

10.
In this study, Extran (biodegradable surfactant) was used for the preparation of Fe3O4 nanoparticles by microemulsion process to improve removal efficiency of As(III) from aqueous solution. Fe3O4 nanoparticles were characterized by XRD, FTIR, FESEM, TEM, HRTEM, and VSM instrumental techniques. The effect of different parameters such as adsorbent dose, initial As(III) concentration, and solution pH were studied by response surface methodology (RSM) based on Box-Behnken design (BBD). The optimized condition for adsorption of As(III) from aqueous solution was obtained as adsorbent dose of 0.70 mg/g, solution pH of 7.7, and initial As(III) concentration of 33.32 mg/L. In this optimum condition, about 90.5% of As(III) was removed from the aqueous solution. Isotherm studies have been done at optimal condition, and it was observed that the Langmuir isotherm models were fitted well with experimental data having a high correlation coefficient of 0.993. From the Langmuir isotherm data, the maximum adsorption capacity of Fe3O4 nanoparticles was found to be 7.18 mg/g at pH 7.7 in room temperature. This study revealed that Fe3O4 nanoparticles can be used as an efficient, eco-friendly, and effective material for the adsorptive removal of As(III) from aqueous system.  相似文献   

11.
Two identical experimental subsurface-flow constructed wetlands were operated at relatively high organic loading rates (23 g COD m?2 day?1) for 4 months to evaluate their relative ability to remove either dissolved organic carbon (glucose, considered to be a readily biodegradable substrate) or particulate organic carbon (starch, considered to be a slowly biodegradable substrate). The systems were built using plastic containers (0.93 m long, 0.59 m wide and 0.52 m high) that were filled with an 0.35 m layer of wetted gravel (D60?=?3.5 mm, uniformity coefficient Cu?=?D60/D10?=?1.7) and the water level was maintained at 0.05 m under the gravel surface to give a water depth of 0.30 m. The results indicated that there was no significant difference in COD removal between the two systems. Both systems generally had COD removal rates of over 90%, which is quite high if the heavy load applied is taken into account. The removal of ammonium was greater in the glucose-fed system (57%) in comparison with the starch-fed system (43%). Based on mass balance calculations and stoichiometric relationships, it was estimated that denitrification and sulphate reduction were minor pathways for the removal of organic matter. Indirect observations allowed to assume that methanogenesis made a highly significant contribution to the removal of organic matter.  相似文献   

12.
Effects of ethanol and nitrate on linear alkyl benzene sulfonate (LAS) degradation were investigated using central composite design. At experimental design, removal of 99.9% was observed in batch reactors (1 L) with 9.8 to 41.2 mg L?1 of LAS. The batch reactors were kept under agitation at 120 rpm and 30 °C. Ethanol (co-substrate) and nitrate (electron acceptor) were statistically significant factors (p?<?0.05) in surfactant removal. Optimal values were 97.5 and 88 mg L?1 for ethanol and nitrate, respectively. LAS removal was kinetically investigated by varying surfactant concentration while using optimal values. Batch I (27 mg L?1 LAS) exhibited greater degradation rate (KLAS) (0.054 h?1) in the presence of ethanol and nitrate. Nonetheless, in Batch II (60 mg L?1 LAS), the KLAS values decreased in those reactors probably due to inhibition by excess substrate for same concentrations of nitrate and ethanol added in reactors. As LAS concentration increased, the dominance of bacterial populations also increased, whereas diversity index decreased from 2.8 (inoculum) to 2.4 and 2.5 for reactors with both added nitrate and ethanol and those with only added ethanol, respectively. Probably, a selection of microbial populations occurred in relation to LAS concentration. The nitrate and ethanol, at able concentration, made it possible the induction of denitrifying microrganisms foward to LAS removal.  相似文献   

13.
The treatment of effluent from anaerobic digestion of organic wastes was carried out using chemical and electrochemical processes, namely, chemical coagulation (CC) with lime, electrocoagulation (EC) with iron consumable electrodes, and electrochemical oxidation (EO) with a boron-doped diamond anode, at different experimental conditions. In the CC assays, the highest chemical oxygen demand (COD) removal, 50%, was achieved for a lime concentration of 70 g L?1 after 2 h experiment. Under the experimental conditions studied, EC promoted COD removals of 80% after 5 h and EO led to COD removals of 43% after 6 h electrolysis, being this last removal increased to 60% when chloride was added to the effluent. A combined EC+EO treatment was also performed, utilizing the most favorable experimental conditions obtained in the individual processes, and global removals of 95% in COD and 44% in ammonia nitrogen were attained after 5 h of EC followed by 6 h of EO. These results proved that the combined process can be an efficient alternative in the treatment of effluents from anaerobic digestion of organic wastes with the characteristics of the studied effluent.  相似文献   

14.
The oxidation of para-nitrochlorobenzene (pNCB) by persulfate (PS) activated with zero-valent iron (Fe0) was investigated through a series of batch experiments. The pNCB reduction ratio increased with the decrease of the initial solution pH. It is found that temperature and Fe0 dosage could also influence the pNCB removal. Under the conditions of initial Fe0 dosage 0.8 mmol/g, initial pH of 6.6, and 25 °C, 66.3% of pNCB was reduced in 6 h. The pNCB was slightly degraded in the presence of PS alone. When PS was dosed after 2 h of Fe0 reduction, significantly higher pNCB removal (94.1%) and mineralization (36.4%) were obtained relative to the case of simultaneous dosing of Fe0 and PS (85.3% removal, 22.6% mineralization). This indicates that the reduction product of pNCB was more easily oxidized by PS than pNCB, suggesting that converting the nitro groups of pNCB to amino groups prior to oxidation can enhance their oxidation. These results suggest that a sequential Fe0 reduction–PS oxidation process may be an effective strategy to promote pNCB decomposition in contaminated soil.  相似文献   

15.
Continual discharge of textile wastewaters loaded with a variety of synthetic dyes and metals is considered as a huge threat to surrounding ecosystems. In order to treat these undesirable pollutants, microbial bioremediation is considered as an efficient and economical technique. This study was conducted to evaluate the use of bacterial strains for simultaneous removal of azo dyes and hexavalent chromium [Cr(VI)]. Fifty-eight bacterial strains were isolated from Paharang drain wastewater and tested for their potential to decolorize reactive red-120 (RR-120) in the presence of 25 mg L?1 of Cr(VI). Among the tested isolates, FA10 decolorized the RR-120 most efficiently and was identified as Acinetobacter junii strain FA10. Based on quadratic polynomial equation and response surfaces given by the response surface methodology (RSM), Cr concentration and pH were found to be the main factors governing the RR-120 decolorization by FA10. The strain FA10 also exhibited a substantial salt resistance since it showed a considerable decolorization of RR-120 even in the presence of 150 g L?1 of NaCl. Moreover, the strain FA10 also showed the potential to simultaneously remove the Cr(VI) and the selected azo dyes in the same medium. More than 80 % of the initially added Cr(VI) was removed over 72 h of incubation along with the appreciable decolorization efficiency. The strain FA10 also exhibited good tolerance to considerable levels of different heavy metals. The findings of this study suggest that the strain FA10 might serve as an efficient bioresource to develop the biotechnological approaches for simultaneous removal of different azo dyes and heavy metals including Cr(VI).  相似文献   

16.
The capacity of microalgae to accumulate heavy metals has been widely investigated for its potential applications in wastewater (bio)treatment. In this study, the ability of Desmodesmus pleiomorphus (strain L), a wild strain isolated from a polluted environment, to remove Cd from aqueous solutions was studied, by exposing its biomass to several Cd concentrations. Removal from solution reached a maximum of 61.2 mg Cd g?1 biomass by 1 day, at the highest initial supernatant concentration used (i.e., 5.0 mg Cd L?1), with most metal being adsorbed onto the cell surface. Metal removal by D. pleiomorphus (strain ACOI 561), a commercially available ecotype, was also assessed for comparative purposes; a removal of 76.4 mg Cd g?1 biomass was attained by 1 day for the same initial metal concentration. Assays for metal removal using thermally inactivated cells were also performed; the maximum removal extent observed was 47.1 mg Cd g?1 biomass, at the initial concentration of 5 mg Cd L?1. In experiments conducted at various pH values, the highest removal was achieved at pH 4.0. Both microalga strains proved their feasibility as biotechnological tools to remove Cd from aqueous solution.  相似文献   

17.
The goal of this research was the electrooxidation (EO) of a nonionic surfactant nonylphenol decaethoxylate (NP-10) in aqueous solution and denim wastewater. Three different configuration systems were evaluated in batch cells using a boron-doped diamond (BDD) anode; copper, iron, and BDD were used as cathodes. The EO process was carried out in a batch process, in a glass cell with a capacity of 1000 mL. The anode surface area was 0.0307 m2 and 1–3 A of current intensity were applied (3, 6, 10 mA/cm2) with an electrolysis time of 240 min for aqueous solution and 780 min for denim wastewater in order to investigate the degradation of the surfactant. The processes were analyzed in terms of chemical oxygen demand (COD) and total organic carbon (TOC). The maximum mineralization efficiency in aqueous solution for the BDD-Cu electrooxidation system was 92.2% for COD and 45.6% for TOC at pH 2 and 3 mA/cm2 of current intensity. For denim wastewater, the removal efficiency was 44.1% for COD and 26.5% for TOC at pH 4.5 and 6 mA/cm2 of current intensity, using a BDD-BDD system. The raw and treated (aqueous solution and denim) wastewater were characterized by UV-Vis and infrared spectroscopy.  相似文献   

18.
The present study deals with the synthesis and subsequent application of Fe3O4@n-SiO2 nanoparticles for the removal of Cr(VI) from aqueous solutions. Rice husk, an agrowaste material, was used as a precursor for the synthesis of nanoparticles of silica. Synthesized nanoparticles were characterized by XRD and SEM to investigate their specific characteristics. Fe3O4@n-SiO2 nanoparticles were used as adsorbent for the removal of Cr(VI) from their aqueous solutions. The effects of various important parameters, such as initial Cr(VI) concentration, adsorbent dose, temperature, and pH, on the removal of Cr(VI) were analyzed and studied. A pH of 2.0 was found to be optimum for the higher removal of Cr(VI) ions. It was observed that removal (%) decreased by increasing initial Cr(VI) concentration from 1.36?×?10-2 to 2.4?×?10-2 M. The process of removal was found to be endothermic, and the removal increased with the rise in temperature from 25 to 45 °C. The kinetic data was better fitted in pseudo-second-order model in comparison to pseudo-first-order model. Langmuir and Freundlich adsorption capacities were determined and found to be 3.78 and 1.89 mg/g, respectively, at optimum conditions. The values of ΔG 0 were found to be negative at all temperatures, which confirm the feasibility of the process, while a positive value of ΔH 0 indicates the endothermic nature of the adsorption process. The present study revealed that Fe3O4@n-SiO2 nanoparticles can be used as an alternate for the costly adsorbents, and the outcome of this study may be helpful in designing treatment plants for treatment of Cr(VI)-rich effluents.  相似文献   

19.
A novel activated carbon has been prepared by the activation of ground pine cones using phosphoric acid activation, and the nitrogen Brunauer?CEmmett?CTeller surface area was 869 m2 g?1. Equilibrium isotherms were performed to assess the capacity of the activated carbon using two acidic dyes, namely Acid Blue 113 and Acid Black 1. The monolayer equilibrium isotherm capacities of Acid Blue 113 and Acid Black 1 were 286 and 458 mg dye/g C, respectively. These capacities are significantly higher than commercial carbons and other literature carbons. For the first time, these carbons were tested in fixed bed experimental systems and data analysed using the bed depth service time model (BDST) and the carbon usage rate (CUR) model. In the fixed bed studies, the key parameters for a 20-cm bed depth for the BDST model at 50% breakthrough capacity are (a) for Acid Black, the BDST capacity is 149 mg dye/g carbon and operating time is 1,530 min and (b) for Acid Blue, the breakthrough capacity is 9 mg of dye/g of carbon and operating time is 195 min. The fixed bed study indicates that the BDST design models can be applied satisfactorily, and the pine cone carbon has significant potential but a more mesoporous pine cone carbon is preferable for the larger Acid Black dye. The CUR design method was not successful.  相似文献   

20.
An optimized co-precipitation process for color removal from Kraft pulp and paper mill effluents is described. The process involves sequential addition of alum and lime under controlled conditions, as well as the influence of selected polyelectrolytes on the degree of color removal. Results obtained were in the range of 86 to 95% removal for caustic extract effluent and whole mill effluent. An Al+3/Ca+2 ratio of 0.23 gave optimal results with a final pH in the 4 to 5 range. The chemicals used in the suggested process are commonly available in most Kraft mills. As well, significant reductions in chemical oxygen demand (COD) were observed during the color removal process. An economic analysis indicates that the process is financially attractive.  相似文献   

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