Defluoridation of Water Using Zirconium Impregnated Coconut Fiber Carbon

Abstract

In this study the applicability of Zirconium ion impregnated coconut fiber carbon (ZICFC) as an adsorbent for fluoride removal from water was investigated. The dependence of fluoride adsorption on the physicochemical properties includes pH, agitation time, adsorbent dosage, temperature, and the initial concentration of the adsorbate. Maximum defluoridation was obtained at an original pH value of 4.0 with a rapid 93% adsorption being achieved within 10 min of contact with ZICFC. Adsorption data for fluoride onto ZICFC were better correlated to the Langmuir isotherm and pseudo-second order chemical reaction provided the best fit for the experimental data as obtained from kinetic studies. A combination of chemisorption and physisorption processes in hand with intraparticle diffusion, account for the high defluoridation ability of ZICFC, with the thermodynamic parameters indicating an endothermic phenomenon. The fluoride adsorption capacity of ZICFC when compared with those of other commonly used fluoride adsorbents highlights the substantial improvement in fluoride adsorption capacity of coconut fiber carbon on zirconium impregnation.     

Kinetic and Equilibrium Study for the Fluoride Adsorption using Pyrophyllite

Batch adsorption study was carried out to remove excess fluoride from water using pyrophyllite. Result showed that adsorption of fluoride was rapid in first 20 min and thereafter increased slowly to reach the equilibrium in about 2 hrs. About 85% removal efficiency was obtained within 2 hrs at an adsorbent dose of 4 g/L for initial fluoride concentration of 10 mg/L. Maximum fluoride adsorption takes place at pH 4.9. Thermodynamic parameters such as Gibb's free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) changes were determined for the adsorption process. Negative ΔH° value signified that the adsorption process was exothermic in nature. From the kinetic study it was found that fluoride adsorption by pyrophyllite followed pseudo-second-order kinetics with an average rate constant of 0.92 g/mg · min. Intraparticle diffusion model was studied to determine the rate limiting step of the adsorption process. The system followed the Langmuir isotherm with maximum adsorption capacity of 2.2 mg/g of fluoride.     

水蒸气法制备椰壳活性炭及其对肌酐吸附效果研究

采用水蒸气活化法制备得到椰壳活性炭,以850℃活化得到微孔率最高的活性炭为吸附剂,考察其对肌酐的体外吸附性能,探讨了吸附时间、肌酐初始质量浓度、吸附温度及pH值对肌酐吸附量的影响。结果表明,微孔率高的（71．0％）椰壳活性炭对肌酐吸附性能良好;30min内吸附量迅速升至57．8mg/g,7h时达到平衡,平衡吸附量为76．4mg/g;在30～70℃温度范围内,肌酐吸附量随温度升高而增加;酸性环境有利于肌酐的吸附,pH值为2时吸附量达到最大,为123．55mg/g。     

硅胶负载氧化锆除氟吸附剂的制备

应用浸渍法制备了硅胶负载氧化锆除氟吸附剂,用正交实验设计安排实验,获得了最佳制备条件。讨论了制备条件如浸渍固液比、浸渍液浓度和温度、浸渍时间和浸渍次数的影响。浸渍液固液比对吸附剂吸附量有较大影响。浸渍液浓度大于0.10 mol/L后吸附剂的吸附量增加缓慢。浸渍2 h后可达到浸渍平衡。浸渍温度高则吸附量变大,多次浸渍可较大幅度地提高吸附量。     

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.     

椰壳活性炭对气态氯化汞吸附作用的对比研究

以氯化汞为目标污染物,研究了椰壳活性炭对气态氯化汞的吸附性能,并结合活性炭微结构表征以及动力学模型拟合研究了其吸附机理。结果表明,椰壳活性炭对气态氯化汞的最大吸附量35.9 mg/g,且活性炭比表面积和总孔容对其吸附氯化汞有显著影响,比表面积大、总孔容大有利于提高饱和吸附量。载气流量不影响活性炭对氯化汞的饱和吸附量,但是影响其吸附时间,增大载气流量能够缩短吸附时间。温度对吸附量和吸附时间均有影响,升高温度能够提高吸附量且缩短吸附时间。通过对吸附过程的动力学模拟,发现活性炭对氯化汞的吸附均符合班厄姆动力学模型,相关系数均大于0.99,活性炭的吸附速率与吸附量随比表面积与总孔容的增大而增大。     

油茶果壳活性炭对苯酚的吸附动力学研究

以油茶果壳制备的活性炭为吸附剂,探讨了温度、苯酚初始浓度对油茶果壳活性炭吸附苯酚性能的影响,并用两种动力学模型进行了拟合。结果表明:油茶壳活性炭对苯酚的吸附是一个较为快速的过程,60 min就可接近吸附平衡。油茶壳活性炭对苯酚的吸附动力学过程可以用准一级与准二级模型进行很好的描述,相关系数达到0.96以上。     

Adsorption of Furfural from Aqueous Solution onto Activated Carbon: Kinetic,Equilibrium and Thermodynamic Study

Abstract

The present study aims to evaluate the influence of various experimental parameters viz. initial pH (pH ₀), adsorbent dose, contact time, initial concentration and temperature on the adsorptive removal of furfural from aqueous solution by commercial grade activated carbon (ACC). Optimum conditions for furfural removal were found to be pH ₀ ≈ 5.9, adsorbent dose ≈ 10 g/l of solution and equilibrium time ≈ 6.0 h. The adsorption followed pseudo‐second‐order kinetics. The effective diffusion coefficient of furfural was of the order of 10^?13 m²/s. Furfural adsorption onto ACC was found to be best represented by the Redlich‐Peterson isotherm. A decrease in the temperature of the operation favorably influenced the adsorption of furfural onto ACC. The positive values of the change in entropy (ΔS ⁰); and the negatived value of heat of adsorption (ΔH ⁰) and change in Gibbs free energy (ΔG ⁰) indicated feasible, exothermic, and spontaneous nature of furfural adsorption onto ACC.     

椰壳活性炭对加替沙星的吸附及缓释性能研究

研究了水溶液中椰壳活性炭对喹诺酮药物加替沙星（GTFX）的吸附性能,测定了不同温度下的吸附等温线并分析了其吸附热力学参数。结果表明：活性炭对加替沙星的吸附符合Freundlich方程,ΔH=-1.7374kJ/mol,说明活性炭对GTFX的吸附过程为放热过程,且ΔH<20kJ/mol,表明吸附过程主要为物理吸附。同时,测得吉布斯自由能ΔG<0,表明吸附质从溶液到吸附剂表面的吸附过程是自发过程,其吸附主要是熵驱动。对椰壳活性炭进行了硝酸及氨水改性,研究了3种不同活性炭对GTFX的缓释性能,结果显示,与椰壳活性炭相比,经硝酸氧化改性后的活性炭缓释性能有较大的提升,而经氨水改性的活性炭缓释性能有所下降,3种不同活性炭对GTFX的缓释均符合Higuchi方程释药模式。     

热解活化法制备高吸附性能椰壳活性炭

以椰壳为原料,采用高温直接热解活化法制备高吸附性能活性炭。研究了活化温度、活化时间对活性炭吸附性能的影响。研究结果表明,活化温度为 900 ℃,热解活化时间为 8 h,升温速率为 10 ℃/min,制得碘吸附值为 1 628.54 mg/g,亚甲基蓝吸附值为 375 mg/g 的高吸附性能椰壳活性炭,得率为 9.41 %。氮气吸附实验结果表明,该活性炭比表面积 1 723 m²/g、总孔容积 0.87 cm³/g、微孔容积 0.68 cm³/g、中孔容积0.18 cm³/g、平均孔径 2.03 nm。热解活化制备的椰壳活性炭样品性能优于市售水蒸气法椰壳净水活性炭国家标准。     

KOH活化法制备椰壳活性炭研究

以椰壳炭化料为原料,采用KOH活化法制备活性炭,研究了KOH/炭化料的质量比、升温速率、活化温度和活化时间对活性性能的影响。实验结果表明,KOH/炭化料的质量比是该方法制备活性炭的最主要影响因素,较优的工艺参数为:KOH/炭化料的质量比为4∶1、升温速率为5℃/min、活化温度为800℃、活化时间为1 h。同时制备得到了比表面积达到2413 m2/g、微孔容积达到1.02 cm3/g,且以0.9 nm以下微孔为主的椰壳活性炭。     

两步法制备椰壳基微孔活性炭

A novel two-step procedure was used to manufacture microporous activated carbon from raw coconut shell. In this process, the raw coconut shell was （1） heated in an inert environment to temperatures between 450℃ and 850℃, and reacted with oxygen （ PO2=1.1-5.3kPa） for some time, and （2） heated again in inert environment to activation temperature（850℃） to produce an activated carbon. Activated carbons with specific surface area greater than 700m^2.g^-1 were manufactured with a yield between 24% and 28%. It was shown that the carbon had a narrow distribution of pore size, possibly less than lnm, which was calculated by a simple method based on local density function theory.     

微波辐射制备椰壳活性炭的研究

以海南椰子壳为原材料,氯化锌作活化剂,采用微波辐射加热制备了活性炭。研究了微波功率、辐射时间、浸泡时间和ZnCl2质量分数对活性炭吸附性能与产率的影响。通过正交实验优化制备条件,在微波功率800 W、辐射时间9 min、浸泡时间48 h、ZnCl2质量分数50%的条件下,所制得的椰壳活性炭样品碘吸附值为1258.34 mg/g,亚甲基蓝吸附值为200.00 mL/g,产率为32.46%,BET比表面积为1395.46 m2/g,总孔容0.7021 cm3/g,孔径集中分布在4～9 nm范围。     

Removal of Phenolic Substances from Water by Adsorption and Adsorption-Ultrafiltration

In this work a magnetic adsorbent, magnetic activated carbon (MAC) was prepared and characterized by powdered X-Ray diffraction (XRD). A comparison was made between powdered activated carbon (PAC) and MAC for foul control in ultrafiltration (UF) membrane processes. First, the adsorptive parameters for PAC and MAC were determined for phenol, chlorophenol, nitrophenol, and hydroquinone. Equilibrium data fitted well to the Langmuir model in the studied concentration range of the adsorbates. Adsorption kinetics followed a pseudo second-order kinetic model rather than pseudo first-order kinetic model. These adsorbents were then used in combination with UF membrane. The parameters like percent rejection and flow rate for the hybrid UF/PAC and UF/MAC were determined. The influences of both adsorbents on flow rates and percent rejections were almost equal. The problems associated with PAC in the UF processes like cake formation and blackening of the pipes were not observed for MAC. MAC was removed from the slurry after use through a magnetic process.     

氯霉素在活性炭上的吸附平衡与动力学

为去除水体中残留的氯霉素,采用生物相容性佳的活性炭作吸附剂,测定了25,30,35℃下氯霉素在自制活性炭上的吸附平衡与动力学,并与商用竹炭作对比。结果表明高比表面积活性炭是去除水体中残留氯霉素的高效吸附剂,活性炭的吸附容量随着吸附剂比表面积和孔容的增大而增大,但随温度从25,30到35℃升高而减小,自制高比表面积活性炭的吸附容量达到3种市售活性炭样品吸附容量的10倍以上;Freundlich吸附等温线方程可较好地描述氯霉素在活性炭上的吸附平衡,准二级方程是用来描述氯霉素在活性炭上吸附的合适动力学模型,并通过拟合得到了其动力学参数。随着温度的升高吸附容量逐渐减小。本研究为活性炭对水体中残留氯霉素的吸附处理提供了科学依据。     

Adsorption Characteristics of Atrazine on Granulated Activated Carbon and Carbon Nanotubes

Adsorption of atrazine (ATZ) from aqueous solutions by granular activated carbon (GAC) and carbon nanotubes (CNT) was studied in a batch‐mode adsorption system at different initial concentrations of ATZ (1.0–30.0 mg L^–1) and at three temperatures of 288, 296 and 304 K. The adsorption isotherms of Langmuir, Freundlich, Polanyi–Manes, and Brunauer–Emmett–Teller (modified) were used to model the process. The adsorption kinetics followed a pseudo‐second‐order kinetic model. The thermodynamic parameters ΔH⁰, ΔS⁰, and ΔG⁰ of the adsorption were estimated. The thermodynamic parameters indicate that the adsorption process is spontaneous and exothermic.     

Thermodynamic and Kinetic Behaviors of Trinitrotoluene Adsorption on Powdered Activated Carbons

Abstract

Regulations on the removal of trinitrotoluene (TNT) from wastewater have become increasingly more stringent, demanding faster, less expensive, and more efficient treatment. This study focuses on the adsorption equilibrium and kinetics of TNT on powered activated carbons (PAC). Three types of PACs (i.e., wood based, coal based, and coconut‐shell based) were studied as functions of temperature and pH. Thermodynamic properties including Gibbs free energy, enthalpy, and entropy, were evaluated by applying the Van't Hoff equation. In addition, the adsorption energy distribution functions which describe heterogeneous characteristics of porous solid sorbents were calculated by using the generalized nonlinear regularization method. Adsorption kinetic studies were carried out in batch adsorber under important conditions such as PAC types, temperature, pH, and concentration. We found that fast and efficient removal of TNT dissolved in water can be successfully achieved by PAC adsorption.     

磷酸活化法制备椰壳基不定型颗粒活性炭

以椰壳为原料,采用磷酸活化法制备椰壳基不定型颗粒活性炭,分析了反应条件对活性炭性能的影响。研究结果表明,随着浸渍比的升高,活性炭醋酸吸附量和醋酸锌吸附量呈不断上升的趋势,表观密度和强度呈下降趋势。活化温度和烘干温度的升高有利于活性炭醋酸锌吸附量、表观密度和强度的提高。在浸渍比1.25:1,活化温度400 ℃和烘干温度120 ℃,制得不定型颗粒活性炭的醋酸吸附量546 mg/g、醋酸锌吸附量61 g/L、表观密度0.395 g/mL和强度84.4%,符合国家标准GB/T 13803.5-1999的要求。     

活性炭对丁酮的吸附动力学研究

研究了2种活性炭（木质活性炭和煤质活性炭）对丁酮的吸附,重点考察了活性炭的吸附时间、吸附温度和丁酮载气流量对丁酮吸附的影响,并用准一级、准二级、Elovich和Bangham 4种动力学模型对活性炭在不同温度条件下对丁酮的吸附行为进行了动力学拟合,确定其动力学吸附模型。实验表明：不同的活性炭对丁酮的吸附过程不同;活性炭对丁酮的吸附是一个吸附和解吸同时存在的过程,当吸附速率和解吸速率相等时,该过程达到吸附平衡;随着吸附温度的升高,活性炭对丁酮的饱和吸附量逐渐降低,说明活性炭对丁酮的吸附过程为放热反应;丁酮载气流量对活性炭吸附丁酮达到饱和的时间以及吸附速率有影响,对AC-1的最终饱和吸附量影响显著,对AC-2的最终饱和吸附量没有显著影响。这2种活性炭吸附丁酮最适宜的吸附温度均为303 K,最佳的载气流量为400 mL/min。在不同温度下对活性炭吸附丁酮的过程进行动力学分析,发现Bangham方程计算得到的相关系数R²大于0.99,因此,活性炭对丁酮的吸附动力学方程符合Bangham动力学方程。     

Adsorption of N-Vinylpyrrolidone from Polyvinylpyrrolidone Solution onto Bamboo-Based Activated Carbon

The adsorption of N-vinylpyrrolidone from aqueous polyvinylpyrrolidone solution using bamboo-based activated carbon was studied. The adsorption isotherms of N-vinylpyrrolidone on the carbon were determined and modeled with the Langmuir, Freundlich, and Temkin models. The Langmuir model provides the best fitting for the equilibrium data and the maximum monolayer adsorption capacity was estimated to be 833.3 mg/g. The kinetics of the adsorption process of N-vinyulpyrrolidone were modeled using various equations including pseudo first-order, pseudo second-order, and intra-particle diffusion equations. The adsorption process follows the pseudo second-order kinetic model, suggesting that the adsorption mechanism is chemisorption. The activation energy for the adsorption is 86.4 kJ/mol. Thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy were determined. The positive value of enthalpy change indicates that the adsorption process is endothermic.