Removal of textile dyes from aqueous solution by conducting polymer modified clinoptilolite

In this work, clinoptilolite was modified with conducting polyaniline polymer and then the nanocomposite was used as an adsorbent for methyl orange (MO) as a model dye. Cations located in clinoptilolite structure like Na⁺, K⁺, Mg²⁺, Ca²⁺ were exchanged with anilinium cations and then the polymerization of anilinium cations in and outside of the clinoptilolite channels resulted in the formation of polyaniline/clinoptilolite nanocomposite. The resulted nanocomposite was used for the removal of MO from aqueous solution. The effect of various factors like contact time, concentration of dye as well as the amount of adsorbent on the removal efficiency of dye was investigated. The adsorption isotherms were investigated. It was found that the equilibrium adsorption data were well described by the Langmuir isotherm model. The kinetic studies indicated that the adsorption process was controlled by pseudo-second-order equation. High adsorption capacity and low contact time as well as the low cost of modified clinoptilolite proved that it is an efficient adsorbent for the removal of MO from aqueous solutions.     

Characterization and adsorption of disperse dyes from wastewater onto cenospheres activated carbon composites

In the present research, coal fly ash, a waste by-product of thermal power plant, has been segregated to obtain hollow and spherical cenospheres which combined with activated carbon in different ratio for effectual remediation of wastewater. Fabricated cenospheres activated carbon (CNAC) composites were characterized by ATR-FTIR, SEM, XRD, BET and CILAS for functionality, surface modification, crystallinity, surface area, pore volume, pore size and particle size analysis, respectively. Batch adsorption has been applied to appraised maximum removal of Disperse Orange 25 (DO) and Disperse Blue 79:1 (DB) dyes at varying solution pH 2 to 12, adsorbent dose 0.1 g cenospheres + 0.1 g AC to 1.0 g cenospheres + 1.0 g AC, dye concentration 10 to 100 mg/L, agitation speed 80 to 240 rpm and contact time 5 to 300 min at three different temperatures (25, 35 and 45 °C). The maximum percentage removal was found to be 79 and 76% for DO and DB dyes, respectively, at optimized condition. Langmuir isotherm showed good interaction with adsorption data, and the obtained maximum equilibrium adsorption capacity was found to be 90.91 mg/g for DO and 83.33 mg/g for DB at 45 °C. Eventually, the negative ?G° (? 7.513 for DO and ? 7.767 for DB) has suggested the feasibility of dyes adsorption on CNAC composites.     

Adsorption of reactive dyes from aqueous solutions by tannery sludge developed activated carbon: Kinetic and equilibrium studies

Adsorption kinetic and equilibrium studies of two reactive dyes, namely, Reactive Red 31 and Reactive Red 2 were conducted. The equilibrium studies were conducted for various operational parameters such as initial dye concentration, pH, agitation speed, adsorbent dosage and temperature. The initial dye concentration was varied from 10 - 60 mg/L, pH from 2–11, agitation speed from 100–140 rpm, adsorbent dosage from 0.5 g to 2.5 g and temperature from 30 °C -50 °C respectively. The activated carbon of particle size 600 μm was developed from preliminary tannery sludge. The dye removal capacity of the two reactive red dyes decreased with increasing pH. The zero point charge for the sludge carbon was 9.0 and 7.0 for the two dyes, respectively. Batch kinetic data investigations on the removal of reactive dyes using tannery sludge activated carbon have been well described by the lagergren plots. It was suggested that the Pseudo second order adsorption mechanism was predominant for the sorption of the reactive dyes onto the tannery sludge based carbon. Thus, the adsorption phenomenon was suggested as a chemical process. The adsorption data fitted well with Langmuir model than the Freundlich model. The maximum adsorption capacity(q⁰) from Langmuir isotherm were found to have increased in the range of 23.15–39.37 mg/g and 47.62–55.87 mg/g for reactive dyes reactive red 31 and reactive red 2, respectively.     

活性碳吸附碘量法测定金

活性炭吸附碘量法测定金对加工样品的设备及伴生元素处理有着重要关系。地区不同、含金颗粒大小不同,设备及处理方法也不同。     

A new preparation process of coal-based magnetically activated carbon

Fe/C-based magnetically activated carbon （MAC） was obtained by carbonizing and activating its precursor, that was prepared by co-precipitation of anthracite coal impregnated in ferric chloride solution. The effect of the concentrations of FeC13 and pH of solution on BET surface area, pore volume and magnetic properties of the MAC was studied by BET N2 adsorption and VSM method. The results indicated that the magnetization of MAC gradually increases with increasing concentration of FeC13 and pH value of solution, and BET surface area was inclined to fluctuation. The largest BET surface area and magnetization of MAC were 1327.5 m2/g and 35.56 emu/g, respec- tively. The form of magnetic matter in the magnetically activated carbon was mainly Fe3C by X-ray powder diffrac- tion （XRD） and magnetic attraction test.     

Biodegradation of anionic surfactants by isolated bacteria from activated sludge

Sodium dodecyl sulphate, (SDS) is an anionic surfactant that widely used all over the world. They will eventually end-up and accumulate in household or industrial sewage. Due to their high foaming capabilities, which can cause numerous problems in sewage treatment facilities as well as direct toxic effects on many different organisms in ecosystem; they are generally considered as serious pollutants. In this survey, two different bacteria were isolated from Tehran municipal activated sludge. Biochemical tests as well as 16S rRNA gene sequencing for identification have been applied. After experiments to optimize the pH and temperature for growth of the two bacterial isolates, the extent of SDS utilization was evaluated by HPLC method. Two bacterial isolates show which ability to rapidly and actively degrade SDS upon using it as their sole source of carbon. The identification tests have indicated the two isolates to be Acinetobacter johnsoni and Pseudomonas beteli. The Pseudomonas beteli and Acinetobacter johnsoni isolates were able to degrade 97.2% and 96.4% of the original SDS levels after 10 days of growth; respectively. Mixed culture of the two isolates did not significantly increase SDS utilization, (97.6%). In conclusion, the results of this study suggest that growth of simple bacteria such as Acinetobacter or Pseudomonas in household and industrial sewage can be cost-effective method anionic surfactants elimination.     

Enhancement of gaseous mercury (Hg0) adsorption for the modified activated carbons by surface acid oxygen function groups

This article discussed the benzoic acid activated carbons which have changed the types and content of acid oxygen-function groups on the surface of activated carbons and their effect on the adsorption for Hg~0 in simulated flue gas at 140 ℃. These surface acid oxygen function groups were identified by Boehm titration, Fourier transformation infrared spectrum, temperature programmed desorption and X-ray photoelectron spectroscopy. It indicates that the carboxyl, lactone and phenolic were formed when the benzoic acid is loaded on the surface of activated carbons. Among the surface acid oxygen function groups, the carboxyl groups enhance the adsorption capacities of Hg~0 for activated carbons to a greater extent.     

Influences of activated sludge surface properties on adsorption of aqueous fullerene C<Subscript>60</Subscript> nanoparticles

Rapid increases in the amounts of fullerene C₆₀ nanoparticles (nC₆₀) being produced and used will inevitably lead to increases in the amounts released into the aquatic environment. This will have implications for human and ecosystem health. Wastewater treatment plants are key barriers to nC₆₀ being released into aquatic systems, but little information is available on how adsorption processes in wastewater treatment plants affect the fates of nC₆₀. We investigated the effects of the surface properties of activated sludge on the adsorption of nC₆₀ and related mechanisms by modeling the adsorption kinetics and equilibrium process and performing correlation analyses. The adsorption of nC₆₀ closely followed the pseudo-second-order kinetic model (R > 0.983), the Freundlich isotherm model (R > 0.990), and the linear partitioning isotherm model (R > 0.966). Different adsorption coefficients, 1.070–4.623 for the Freundlich partitioning model and 1.788–6.148 for the linear partitioning model, were found for different types of activated sludge. The adsorption coefficients significantly positively correlated with the zeta (ζ) potential (R = 0.877) and hydrophobicity (R = 0.661) and negatively correlated with particle size (R = ?0.750). The results show that nC₆₀ adsorption is strongly affected by the surface properties of activated sludge because changes in surface properties cause changes in the electrostatic and hydrophobic interactions that occur.     

Biodegradation of Cypermethrin by Pseudomonas in a batch activated sludge process

The biodegradation of Cypermethrin (20 to 125 mg/L) in an effluent using batch activated sludge was studied. Degradation was found to occur to a great extent only in the presence of Pseudomonas (IES-Ps-1) culture. Under aerobic conditions using mechanical aerators, Cypermethrin (20 mg/L) was almost completely degraded in just over 48 h at ambient temperature. Further loading of organic compound in subsequent experiments demonstrated that IES-PS-1was capable to degrade 82 % Cypermethrin at 40 mg/L dose in approximately 48 h. When the concentration was increased to 80 mg/L, 50% degradation of this compound was observed. Over this time period the cells could utilize only 17 % of Cypermethrin when it was given 125 mg/L, respectively. These findings indicate that increased concentration of Cypermethrin has a marked effect on biodegradation performance of IES-Ps-1 with a modest increased in the duration of lag phase, but did not lead to complete inhibition or cell death. These results proved that IES-Ps-1 is responsible for Cypermethrin degradation. Such finding may be useful in designing a scale-up in situ or on-site hazardous waste bioremediation process for field application.     

改性污泥复合材料时间效应三轴力学特性试验研究

采用水玻璃、生石灰和絮状木质纤维作为污泥改性剂对城市污泥改性后,在不同养护龄期和不同改性剂配比下对改性污泥复合材料开展三轴固结不排水力学强度和破坏特征试验研究。改性剂设置3种配比5%、10%和15%,在相同围压下,养护5 d改性污泥复合材料破坏强度相对于原污泥相应地提高到1.25～1.426、1.12～1.33、1.2～1.5;养护10 d分别提高到1.33～1.45、1.154～1.35、1.56～1.67,改性剂配比5%和10%试验比15%硬化速度较快。养护10 d改性污泥在主应力差为20 kPa时,初始切线模量发生很大的突变,并且10%和15% 组有3%～5%应变延时期。养护10 d时5%和10%配比的试样内摩擦角 值大于15%配比的试样,而黏聚力 值明显小于15%配比的试样。基于Konder应力-应变双曲线方程,利用主应力差渐近值作为归一化因子,建立改性污泥在三轴固结不排水条件下的主应力差-应变关系方程     

Environmental biological model based on optimization of activated sludge process

A simplified environmental biological model has been developed based on biodegradation kinetics correlation to regulate and optimize wastewater treatment system of activated sludge process. All parameters included in the model are calibrated in accordance with reference data and experimental results and good agreements are achieved between calculated results and reference data or experimental results. The minimum bioreactor volume is used as objective function in the model and errors between optimal minimum volume of the model and each reported result of three references are found to be no more than 8.63 % after validation. Comparisons between optimal results and experimental data demonstrate that the deviations are negligible. The optimal minimum volume is 9.21 m³ with the error of 6.40 % to the practical bioreactor volume of a pilot treatment system. The environmental biological model has been applied to economically evaluate a former treatment system with native bacterium YZ1 and four operation periods of the pilot system with functional strain Fhhh compared with YZ1, Fhhh possesses higher biodegradation ability in purified terephthalic acid wastewater and a broader economic potential in the field of wastewater treatment.     

Removal of fluoride from aqueous solution by modified fly ash

Removal of fluoride from aqueous solution by modified fly ash was studied in batch model. The influences of the contact time, the initial F^- concentration, the dosage of fly ash, and the temperature on removal of F have been studied, respectively. It was found that fly ash modified with dilute HCl has the maximum adsorption of fluoride from aqueous solutions, and that the retention of fluoride ions by material was 85% or higher with initial 10 mg F^-/L. First-order kinetics was observed for the adsorption process, which follows the Langrnuir and Freundlich isotherms. The thermodynamic parameters such as ΔG0, ΔH0, ΔS0 were calculated from Langmuir constants. The positive value of ΔH0 （1.273 J/mol） confirms the endothermic nature of adsorption.     

坡缕石粘土对有机染料的吸附热力学研究

将甘肃靖远坡缕石粘土分离提纯,通过静态吸附实验,研究了坡缕石对水中有机染料亚甲基蓝、结晶紫和苯胺蓝的吸附等温线,探讨了吸附热力学特征.实验结果显示,在实验温度范围内3种染料在坡缕石上的吸附在30 min可达平衡,吸附等温线均能较好符合Langmuir模型,饱和吸附量大小顺序为:结晶紫＞亚甲基蓝＞苯胺蓝;吸附均为吸热过程,亚甲基蓝、结晶紫和苯胺蓝的吸附焓分别为15.52、9.26和2.59 kJ/mol;吸附Gibbs函数约为-35～-30 kJ/mol,吸附熵均大于零,吸附是自发过程.     

Enhanced control of activated sludge process using predetermined set-points

The performance of activated sludge process (ASP) is evaluated by the effluent quality which is determined by five different variables of the treated wastewater such as ammonia, total nitrogen, COD, BOD₅ and TSS. To keep these five variables within the limits as per environmental regulations, nitrate and nitrite concentration (S _NO) in the second anoxic reactor and the dissolved oxygen concentration (S _O) in the last aerobic reactor of the ASP should be maintained at prescribed levels. To do that, a closed-loop control configuration is required and proper set-points for these closed-loop control configurations are needed. In this paper, the optimal values of controller set-points are determined for nitrogen removal in the activated sludge process. Effluent quality limits have been considered to evaluate the optimal set-points for the Indian climatic conditions. Once the optimal set-points are determined, PI controllers are used to control S _NO in the second anoxic reactor and S _O in the last aerobic reactor of the ASP. Further, feed-forward control is incorporated to minimize the effect of disturbances, which enters along with the influent. No case studies of BSM1 model have been reported in the literature for the Indian wastewater. In this work, the dynamic simulation of an activated sludge process is performed using the data collected from the sewage treatment plant, located in India. The results of the simulation showed that feed-forward with PI control strategy, ASP can be efficiently controlled without any effluent violations, when compared to BSM1.     

Removal of cyanide from aqueous solutions by plain and metal-impregnated granular activated carbons

In this study, the removal of free cyanide from aqueous solutions by activated carbon was investigated. Effects of metal impregnation (Cu and Ag), aeration, and concentrations of adsorbent and cyanide on the rate and extent of the removal of cyanide were studied. The results have shown that the capacity of activated carbon for the removal of cyanide can be significantly improved (up to 6.3-fold) via impregnation of activated carbon with metals such as copper and silver. Silver-impregnated activated carbon was found to be the most effective at the reduction of cyanide level in solution. This appeared to be coupled with its comparatively high metal content after impregnation process where silver (5.07%) could be more readily loaded on activated carbon than copper (0.43%). Kinetics and equilibrium data for cyanide removal by plain and metal-impregnated activated carbons were determined to be consistent with the pseudo second-order kinetics and the Langmuir adsorption isotherms, respectively. Aeration (0.27 l/min) was found to exert a profound effect on the process leading to a 5.5–49.1% enhancement in the performances of plain and metal-impregnated activated carbons. This enhancement could be attributed to the increase in the availability of active sites on activated carbon for adsorption and the catalytic oxidising activity of activated carbon in the presence of oxygen. Practical limiting capacity of plain, copper- and silver-impregnated activated carbons for the removal of cyanide were experimentally determined to be 19.7, 22.4 and 29.6 mg/g, respectively.     

Equilibrium data and process design for adsorption of disperse dyes onto Alunite

Adsorption of disperse dyes from aqueous solutions onto calcined alunite has been investigated to assess the possibility of using alunite for removing disperse dyes from aqueous solutions. The effects of particle size, adsorbent mass, initial pH and temperature of the dye solution on the adsorption capacities have been evaluated. Acidic pH was favorable for the adsorption of all dyes: Disperse Blue 56 (DB56), Disperse Red 74 (DR74) and Disperse Yellow 119 (DY119). The experimental data were correlated reasonably well by the Langmuir isotherm and the isotherm parameters (K_L and a_L) have been calculated. The adsorption capacities were found to be 498, 525 and 500 mg of dye per g of calcined alunite for DB56, DR74 and DY119, respectively. The single-stage batch adsorber design of the adsorption of disperse dyes onto alunite has been studied based on the Langmuir isotherm equation.