Removal of Fluoride from Aqueous Solution Using Aluminum-Impregnated Chitosan Biopolymer

Abstract

Aluminum impregnated chitosan (AIC) was prepared and applied as an adsorbent for the removal of fluoride from aqueous solutions. The process involved two stages: (i) isolation of chitosan from chitin, (ii) impregnation of aluminum in isolated chitosan at fixed pH. SEM and EDS techniques were used to characterize the composition of adsorbent AIC. Dynamic adsorption experiments on AIC were carried out at various pH, contact times, adsorption dosages, and initial fluoride concentration to determine optimum adsorption properties. The experimental data were analyzed using two adsorption models, Langmuir and Freundlich, with the later system providing the best fit. Thermodynamic parameters showed the adsorption process as spontaneous and endothermic. The adsorption process follows first-order kinetics for which a mechanism has been proposed. Reusability of the AIC was tested up to four consecutive cycles. The desorption experiment showed 92% elution of adsorbed fluoride at a pH of 12. Finally, the performance of the adsorbent material was studied on field water samples collected from a fluorosis endemic-region.     

改性铝锆柱撑膨润土去除水中氟离子

采用微波辅助制备锆铝柱撑膨润土(MAZPB)作为吸附剂,研究其对水中F-的去除性能,探讨了MAZPB投加量、溶液pH值、水中共存离子、再生能力等对氟吸附的影响. 结果表明,在较宽的pH范围(3.5~10)内,MAZPB有较好的除氟效果,去除率均达89%以上. 高浓度的Fe3+及CO32-共存能明显抑制MAZPB对氟的吸附. 该吸附过程遵循Lagergren拟二级反应动力学. MAZPB吸附F-符合Freundlich吸附等温模型. 在实验条件下的吸附体系中,吸附机制主要为物理吸附. 采用明矾对吸附F-饱和的MAZPB进行再生后,其对F-的去除率仍达81.93%.     

饮用水除氟技术研究进展

文章论述了饮用水的除氟方法,介绍了目前大规模使用的沉淀分离法,如混凝沉淀法、电凝聚法、电渗析法等,以及吸附分离法,如骨炭法、活性氧化铝法、沸石法、活性炭法、反渗透法、离子交换法等。文章阐述了各种除氟技术存在的优缺点,并对各种除氟技术的机理进行了详细的解析。此外,针对目前饮用水除氟技术,提出了几点建议。     

改性骨炭去除饮用水中氟离子的研究

文章旨在研究改性骨炭对饮用水中氟离子的去除效果。用AlCl3对常见的骨炭进行改性,并考察了pH、氟溶液初始浓度、温度及吸附剂用量对氟离子吸附去除的影响。结果表明:经AlCl3溶液改性的骨炭,用量为0.2 g/L时,其在24 h内对10 mg/L氟离子的去除率达97%以上。该吸附剂比未改性效果好,具有一定的应用前景。     

饮用水沸石除氟的实验研究

本文通过静态搅拌实验和恒温震荡实验研究了接触时间、pH值、温度对沸石除氟效果的影响 ;测定了在 2 5℃时沸石除氟的吸附等温线 ,并对吸附等温线进行拟合 ,证明其符合Langmuir吸附等温式qe=0 .0 68Ce/(1 0 .0 868Ce) ;对吸附速度进行了数学处理 ,证明其符合斑厄姆吸附速度公式dq/dt=0 .0 0 1 8(qe-q) /t0 .2 2 。     

Adsorptive Removal of Co and Sr Ions from Aqueous Solution by Synthetic Hydroxyapatite Nanoparticles

Hydroxyapatite nanoparticles were synthesized by using the precipitation method with simulated body fluid solution and applied for adsorption of Co²⁺ and Sr²⁺ in aqueous solution. The single- and bi-solute adsorption experiments were performed to evaluate the maximum adsorption capacity of hydroxyapatite nanoparticles for Co²⁺ and Sr²⁺, the effect of temperature and pH, and the influence of simultaneous presence of other competing metal ion in a binary system. The synthesized hydroxyapatite nanoparticles had high adsorption capacity for Co²⁺ and Sr²⁺ due to a high specific surface area. The maximum adsorption capacity and binding energy of Co²⁺ were higher than those of Sr²⁺ in single-solute adsorption. The extended Langmuir model was fitted well for bi-solute competitive adsorption of Co²⁺ and Sr²⁺ onto the hydroxyapatite nanoparticles. Thermodynamic analysis showed that adsorption occurred spontaneously for both metals and was endothermic for Co²⁺, but exothermic for Sr²⁺.     

饮用水除氟方法及其机理

综述了近年来国内外饮用水除氟方法,如石灰沉淀法、混凝沉降法、吸附与离子交换法、电凝聚法、电渗析法、反渗透法等。同时讨论了各种除氟方法的机理及进展。     

Removal of Chlorophenols from Aqueous Solution by Anion-Exchange Resins

Abstract

The effects of pH value and chloride ion concentration on the removal of chlorophenols from aqueous solutions by Purolite A-510 resin [macroreticular polystyrene-divinylbenzene resin with R(CH₃)₂(C₂H₄OH)N⁺ group] are discussed by the species distributions of chlorophenols. Those chlorophenols include phenol, 2-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol. The investigations showed that the chlorophenols could be removed effectively at alkaline conditions where the ion-exchange reaction was dominant. Also, the removal of chlorophenols increased with the number of chlorine atoms on the chlorophenols. The removal of chlorophenols via the ion-exchange reaction was hindered by the presence of chloride ions. The effect of chloride ions, however, was diminished in acidic solutions where the adsorption reaction was dominant. The proposed equilibrium model, which considers both adsorption and ion-exchange reactions, adequately describes the sorption behavior of chlorophenols. The partition constants of the protonated chlorophenols can be estimated from the octanol/water partition coefficients of the phenolic compounds.     

磷化铝处置残渣除氟实验研究

对含氟废水和含氟废渣中氟的去除,采用磷化铝处置残渣进行除氟实验研究.结果表明,含氟废水在pH为8～10,磷化铝处置残渣加入量为w=10％,0.1％PAM加入w=1％的条件下,废水中氟从1250 mg/L降至7.5 mg/L,除氟率达99.4％.处理后的含氟废水中氟低于GB8978-1996《污水综合排放标准》中氟化物(...     

利用工业废料制备除氟剂

本文以粉煤灰、红泥、氯化铝、氯化铁为原料,采用正交试验方法制备了新型粉煤灰除氟剂,结果表明所制备的除氟剂的静态饱和吸附容量可达2.36mgF~-/g。     

碳酸钙和氧化钙脱除煤气中H2S和COS的研究

采用热重分析法在常压下对CaCO3和CaO分别脱除H2S和COS的反应进行了研究。结果表明,脱除H2S和COS的反应初速率分别与H2S分压和COS分压成正比;CaO脱除H2S和COS的反应速度与颗粒粒度成反比,与颗粒的比表面积成正比例。与CaO脱除H2S和COS的反应相比,CaCO3脱除H2S和COS反应的初速率慢得多。     

Comparison of Basic Dye Crystal Violet Removal from Aqueous Solution by Low-Cost Biosorbents

Abstract

The removal of basic dye crystal violet by low-cost biosorbents was investigated in this study using a batch experimental system. The adsorption of crystal violet onto various adsorbents was solution pH-dependent and the maximum removal occurred at basic pH 10.0. The kinetic experimental data were analyzed using pseudo-first-order and pseudo-second-order equations to examine the adsorption mechanism and the intraparticle diffusion model to identify the potential rate controlling step. These results suggested that the adsorption of crystal violet onto various adsorbents was best represented by the pseudo-second-order equation. The suitability of the Langmuir and Freundich adsorption isotherms to the equilibrium data was also investigated at various temperatures for all four sorbents and the adsorption isotherms exhibited Freundlich behavior. The Freundlich constant K_f was 1.55 for alligator weed, 2.33 for Laminaria japonica, 9.59 for rice bran and 5.38 (mg/g)/(mg/L)^1/n for wheat bran, respectively at adsorbent concentration 5 g/L, pH 10.0 and 20°C. The thermodynamic parameters (ΔH, ΔG, and ΔS) were calculated and the results showed that the adsorption process for various adsorbents was spontaneous, endothermic, with an increased randomness, respectively. The particle size and the reaction temperature exhibited an insignificant impact on the adsorption equilibrium of crystal violet. The adsorbents investigated could serve as low-cost adsorbents for removing the crystal violet from aqueous solution.     

火电厂脱硫废水除氟技术

该文在现有的各种除氟方法研究基础上,探索出电厂脱硫废水降氟的最有效的方法,即采用化学沉淀法/混凝法来去除电厂脱硫废水中氟化物。通过一系列条件选择试验,确定了适宜沉淀剂为Ca(OH)2、适宜混凝剂为Al(2SO4)3,最佳Ca/F为1∶1.5、最佳Al/F为3∶2。还以0.1%聚丙烯酰胺(PAM)作为助凝剂做探讨试验,找出进一步深度处理氟化物适宜的VPAM。结果表明:该除氟体系可将含氟140~200 mg/L的废水降至10 mg/L以下,符合我国工业废水排放标准(GB 8978—1996)。     

Removal of Cr(VI) From Aqueous Solution by Turkish Vermiculite: Equilibrium,Thermodynamic and Kinetic Studies

Abstract

The adsorption of Cr(VI) from aqueous solution by Turkish vermiculite were investigated in terms of equilibrium, kinetics, and thermodynamics. Experimental parameters affecting the removal process such as pH of solution, adsorbent dosage, contact time, and temperature were studied. Equilibrium adsorption data were evaluated by Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models. Langmuir model fitted the equilibrium data better than the Freundlich model. The monolayer adsorption capacity of Turkish vermiculite for Cr(VI) was found to be 87.7 mg/g at pH 1.5, 10 g/L adsorbent dosage and 20°C. The mean free energy of adsorption (5.9 kJ/mol) obtained from the D–R isotherm indicated that the type of sorption was essentially physical. The calculated thermodynamic parameters (ΔG ^o , ΔH ^o and ΔS ^o ) showed that the removal of Cr(VI) ions from aqueous solution by the vermiculite was feasible, spontaneous and exothermic at 20–50°C. Equilibrium data were also tested using the adsorption kinetic models and the results showed that the adsorption processes of Cr(VI) onto Turkish vermiculite followed well pseudo-second order kinetics.     

Modification of Sodium Alginate for the Removal of Cd(II) from Aqueous Solutions

Sodium alginate was protonated using HCl in ethanol: H₂O mixture (30:70). The modified sodium alginate (MSA) was characterized by determination of carboxyl content and solubility percent. The modified sample acquires of 450 meq-COOH/100 g sample and exhibits the complete insolubility in water. The MSA was utilized as adsorbent material to remove Cd(II) ions from aqueous solutions. Factors affecting adsorption process, such as agitation time and adsorbent concentration and pH of the adsorbate, were examined. The adsorption data show that the maximum adsorption capacity, Q_max, of Cd(II) onto MSA is 769.23 mg/g. The adsorption data also showed that the adsorption of Cd(II) onto MSA obeys Langmuir and Freundlich isotherms.     

Removal of Cationic Dyes from Aqueous Solution by Hydrophobically Modified Poly(acrylic Acid) Hydrogels

Hydrophobically modified poly(acrylic acid) hydrogels were synthesized using acrylic acid (AA), methyl methacrylate (MMA), ethyl methacrylate (EMA) and butyl methacrylate (BMA) as copolymer monomers. These hydrogels were carried out for removal cationic dyes from aqueous solution. It was found that the adsorption of cationic dye depended on the length of the side chain, hydrophobic monomer (MMA, EMA and BMA) content and pH of the solution. Increasing the hydrophobic monomer content led to an increase in the adsorption of cationic dyes on the hydrogels. The adsorption kinetics and isotherms of hydrogels were in good agreement with pseudo–second-order equation and the Langmuir equation, respectively. The cationic dyes adsorption of hydrogels involved a mechanism that combined swelling and electrostatic and hydrophobic interaction.     

泡沫分离法除去水溶液中微量铜离子的工艺

以十二烷基苯磺酸为表面活性物质,自制的单金属离子水溶液为研究体系,对泡沫分离法除去水溶液中金属离子的工艺进行了研究,重点考察了溶液的pH、鼓泡气体流量、表面活性剂浓度及泡沫塔装液量的影响. 结果表明,十二烷基苯磺酸具有良好的起泡性能,对水溶液中铜离子的去除效果也比较理想,最佳操作条件下富集比为18.2,去除率为96.1%,与常规的表面活性剂十二烷基硫酸钠相比,十二烷基苯磺酸在泡沫分离过程结束后不会在体系中残留金属离子,这为探索脱盐新方法提供了依据.     

Simultaneous Removal of Fluoride and Arsenic from Aqueous Solution using Activated Red Mud

Red mud, a waste tailing from alumina production, was activated with calcination and acid treatment for simultaneous removal of F^? and As from water solution. After activation, the specific area and Si-O-M and Al-O-H functional groups of the activated red mud (ARM) greatly increased. Results showed that the adsorption equilibrium time for F^?, As(V), and As(III) was 18, 12, and 48 h, respectively. Kinetic data revealed that adsorption kinetics well followed the pseudo-second order model for F^?, As(V), and As(III). The presence of As(V)/As(III) improved the adsorption rate of F^?. With the co-existence of F^? and As, F^? adsorption was independent of initial solution pH between 4.0 and 10.0, and As adsorption between 2.0 and 10.0. Adsorption of F^?, As(V), and As(III) was better described by the Langmuir model than the Freundlich model, indicating that adsorption was in the form of a monolayer. Fluoride had a significant effect on As(V) adsorption, while the less affected As(III) adsorption. The presence of 1.0 mg/L As(III)/As(V) had no significant influence on F^? adsorption. ARM had high adsorption capacity for F^?, As(V), and As(III), which resulted from the increases in the specific area and Si-O-M and Al-O-H functional groups. Results demonstrated that ARM is a potential adsorbent for simultaneous removal of F^? and As from contaminated groundwater.     

Removal of Fluoride from Contaminated Drinking Water using Unmodified and Aluminium Hydroxide Impregnated Blue Lime Stone Waste

Abstract

The adsorption of fluoride on lime stone (LS) and aluminium hydroxide impregnated lime stone (AlLS) was investigated using a batch adsorption technique. A series of experiments were under taken in an agitated batch adsorber to assess the effect of the system variables such as solution pH, dye concentration and temperature. Removal of fluoride was observed to be the most effective at pH 8. The langmuir and Freundlich isotherm models were applied to the equilibrium data. The results showed that the Freundlich equation fits better than the Langmuir equation. The maximum sorption capacities for the LS and AlLS adsorbents were found to be 43.10 mg/g and AlLS 84.03 mg/g respectively. The FTIR studies indicate that the adsorption of fluoride is physiorption. The adsorption of fluoride onto AlLS proceeds according to a pseudo-first-order model. The results reveal that the LS and AlLS can be economical for the removal of fluoride compared to many other expensive adsorbents.     

Removal of Fluoride from Geothermal Water by Electrodialysis (ED)

Abstract

Removal of fluoride from geothermal water by electrodialysis (ED) was studied. ED operation was performed according to two methods. In the first method, before the ED operation, the pH of geothermal waters was adjusted to 7?7.5 by the addition of the HCl solution to prevent the precipitation of divalent salts in the concentrate compartment. In the second method, geothermal water was pretreated to precipitate the calcium ions. It was obtained that fluoride was effectively removed from geothermal water by electrodialysis using both of these pretreatment methods. However, it is preferable to use the first method because of its technically simple procedure and lower cost of chemicals used.