微波辅助制备柱撑膨润土对刚果红的吸附性能

用微波辅助制备锆铝柱撑膨润土,考察其对废水中刚果红染料的吸附行为,并对吸附前后柱撑膨润土进行表征,以探索吸附机理. 结果表明,在原始溶液pH和室温条件下,初始浓度为50 mg/L的刚果红溶液,吸附剂用量为4 g/L时,吸附45 min后即能达到吸附平衡,柱撑膨润土的吸附容量为12.17 mg/g,脱色率达97.64%;其吸附过程符合准二级动力学方程,粒子扩散不是唯一的速率控制步骤;锆铝柱撑膨润土对刚果红的等温吸附符合Langmuir方程;XRD与FT-IR表征结果表明,吸附过程主要以物理吸附为主.     

Adsorption of Lead and Cadmium on Ca-Deficient Hydroxyapatite

A Ca-deficient hydroxyapatite(d-HAp) has been used to remove lead and cadmium from their mixed ions solution. The effect of pH, coexistent calcium and magnesium ions, and humic acid on the adsorption efficiency were investigated. The results showed that this d-HAp adsorbed both Cd²⁺ and Pb²⁺ efficiently within a wide pH range. The existence of humic acid reduced the removal efficiency of Cd²⁺ and Pb²⁺. The addition of Ca²⁺ and Mg²⁺ with a concentration of 500 mg/L only slightly reduced the removal efficiency. The adsorption kinetics was described by pseudo-second-order reaction model and the adsorption isotherm followed the Langmuir model.     

Low cost adsorbents obtained from ash for copper removal

We investigated the utilization of ash and modified ash as a low-cost adsorbent to remove copper ions from aqueous solutions such as wastewater. Batch experiments were conducted to determine the factors affecting adsorption of copper. The influence of pH, adsorbent dose, initial Cu²⁺ concentration, type of adsorbent and contact time on the adsorption capacity of Cu²⁺ from aqueous solution by the batch adsorption technique using ash and modified ash as a low-cost adsorbent were investigated. The optimum pH required for maximum adsorption was found to be 5. The results from the sorption process showed that the maximum adsorption rate was obtained at 300 mg/L when a different dosage of fly ash was added into the solution, and it can be concluded that decreasing the initial concentration of copper ion is beneficial to the adsorption capacity of the adsorbent. With the increase of pH value, the removal rate increased. When the pH was 5, the removal rate reached the maximum of over 99%. When initial copper content was 300 mg/L and the pH value was 5, the adsorption capacity of the zeolite Z 4 sample reached 27.904 mg/g. The main removal mechanisms were assumed to be the adsorption at the surface of the fly ash together with the precipitation from the solution. The adsorption equilibrium was achieved at pH 5 between 1 and 4 hours in function of type of adsorbent. A dose of 1: 25 g/mL of adsorbent was sufficient for the optimum removal of copper ions. For all synthesized adsorbents the predominant mechanism can be described by pseudo-second order kinetics.     

Polymer hydrogel cross-linked by inorganic nanoparticles for removing trace metal ions

Hydrogels for absorbing metal ions in wastewater have attracted more attentions in the environmental field especially for recent years. The removal efficiency of hydrogel adsorbents for eliminating metal ions is highly related with the effective contact between adsorbents and adsorbates. However, poor water absorption capacity of the hydrogel adsorbents would restrict on the expose of adsorption sites to the targeted subjects, causing undesirable removal ratio (RR) especially for metal ions at trace level. Thereby, the reported hydrogel adsorbents mainly focus on the removal of high content but not the trace level of metal ions so far. In this work, poly(acrylamide) (PAM)/poly(acrylic acid) (PAA)/Ca(OH)₂ composite hydrogel is applied to adsorb trace metal ions. Swelling ratio of such PAM/PAA/Ca(OH)₂ gel reaches 2,530 g/g, resulting in effective exposure of active sites and further expected RR for trace metal ions. The RRs of such adsorbent for Cu²⁺ (initial concentration C₀ = 0.064 mg/L), Al³⁺ (C₀ = 0.27 mg/L), Co²⁺ (C₀ = 0.59 mg/L), Cr⁶⁺ (C₀ = 0.52 mg/L), Mn²⁺ (C₀ = 0.55 mg/L), Ni²⁺ (C₀ = 0.59 mg/L), Zn²⁺ (C₀ = 0.65 mg/L), Ag⁺ (C₀ = 1.08 mg/L), and La³⁺ (C₀ = 1.39 mg/L) are 56.6, 80.8, 41.3, 29.3, 34.6, 44.6, 55.9, 45.8, and 35.5%, respectively. This work broadens the application of hydrogel adsorbent for eliminating trace metal ions from polluted water.     

Cadmium adsorption on modified chitosan‐coated bentonite: batch experimental studies

BACKGROUND: Several researchers have investigated the use of chitosan as an adsorbent for removal of heavy metals from aqueous streams. Chitosan flake or powder swells and crumbles making it unsuitable for use in an adsorption column. Chitosan also has a tendency to agglomerate or form a gel in aqueous media. The adsorption capacity can be enhanced by spreading chitosan on physical supports that can increase the accessibility of the metal binding sites. Although several attempts have been made to enhance the adsorption capacity of chitosan, using various chemicals, the sorption capacity for metal ions decreased after cross‐linking of chitosan. RESULTS: Bentonite was coated with chitosan (Chi) and its derivative, 3,4‐dimethoxy‐benzaldehyde (Chi/DMB). The product was then used as adsorbent for the removal of Cd²⁺ from aqueous solutions. The presence of imine groups resulting from chemical modification was confirmed using IR, DRS and SEM. The adsorption followed the Langmuir isotherm and could be described by pseudo‐second order kinetics. CONCLUSION: Chi/DMB coated on bentonite increased the accessibility of metal binding sites. The Chi/DMB/bentonite showed no significant pH dependence in the pH range 2–9, but bentonite coated with chitosan revealed very intensive pH dependence, which had a considerable effect on cadmium removal. As expected adsorption of Cd²⁺ by Chi/bentonite and Chi/DMB/bentonite is dependent on contact time and adsorbent dose. In addition, an EDTA solution is suitable for desorption of cadmium ions, and the reusability of Chi/DMB/bentonite is quite good. © 2012 Society of Chemical Industry     

CTAB改性铁柱撑膨润土对苯酚的吸附

为了研究膨润土对含酚废水的吸附性能,采用羟基铁柱撑剂对钠基膨润土进行预改性,随后用十六烷基三甲基溴化铵(CTAB)改性,制备CTAB改性铁柱撑膨润土。利用X射线衍射仪(XRD)、红外光谱仪(FTIR)和场发射扫描电镜(FESEM)对改性膨润土的结构和性能进行表征。考察了吸附剂用量、吸附时间、吸附温度、苯酚初始浓度和pH值对吸附性能的影响,研究了吸附热力学和吸附动力学规律。结果表明,CTAB进入铁柱撑膨润土的层间和表面。当吸附剂用量为3 g·L^-1、吸附时间为60 min、吸附温度为25 ℃、苯酚初始浓度为300 mg·L^-1、苯酚初始pH值为7时,改性膨润土吸附量达到29.7 mg·g^-1,吸附过程符合准二级动力学模型和Freundlich热力学模型。     

Preparation and Application of a Novel Functionalized Coconut Coir Pith as a Recyclable Adsorbent for Phosphate Removal

Abstract

This study was to develop a new adsorbent, Iron(III) complex of an amino-functionalized polyacrylamide-grafted coconut coir pith (CP), a lignocellulosic residue, for the removal of phosphate from water and wastewater. The kinetics of adsorption follows a pseudo-second-order model. The equilibrium sorption capacity of 96.31 mg/g was determined at 30°C from the Langmuir isotherm equation. Complete removal of 16.4 mg/L phosphate in 1 L of fertilizer industry wastewater was achieved by 1.5 g/L AM-Fe-PGCP at pH 6.0. The acid treatment (0.1 M HCl) and re-introduction of Fe³⁺ lead to a reactivation of the spent adsorbent and can be reused through many cycles of water treatment and regeneration without any loss in the adsorption capacity.     

膨润土-活性炭复合吸附剂对锰离子的吸附

以膨润土和活性炭为原料制备了复合吸附剂并将之应用于含锰离子废水的吸附。考察了不同条件下该吸附剂对水体中Mn（Ⅱ）的去除效果,并研究了吸附动力学特征和等温吸附过程。结果表明膨润土和活性炭复合吸附剂对Mn（Ⅱ）具有优良的吸附能力,在25 ℃下,当投加量为4 g/L、Mn（Ⅱ）初始质量浓度为50 mg/L、溶液pH为6时,吸附180 min,吸附率为93.2%。准一级、准二级动力学和内扩散模型用来拟合吸附过程,结果表明准二级动力学符合该吸附过程,吸附速率常数为0.003 6 g/（mg·min）,内扩散过程不是吸附的限速步骤,还存在吸附机制的制约。用Langmuir和Freundlich模型描述吸附等温过程,结果得出该吸附过程服从Langmuir吸附,饱和吸附容量为27.781 mg/g。     

Use of CaCl2 modified bentonite for removal of Congo red dye from aqueous solutions

CaCl₂ modified bentonite (BCa²⁺), a clean and cost-effective adsorbent with a basal spacing of 15.43 Å, was prepared for the removal of Congo red dye from water. It was effective for the removal of Congo red with a high adsorption capacity, and the adsorption was favored over a broad pH range (5-10). The pseudo-second-order kinetic model provided the best correlation of the experimental data. Adsorption isotherms indicated that sorption took place at specific homogeneous sites within the adsorbent. Furthermore, BCa²⁺ showed higher sorption capacity compared with other common materials used as adsorbents for Congo red dye. The results showed that BCa²⁺ could be employed as a low-cost material for the removal of Congo red from aqueous solutions.     

柱撑膨润土吸附水溶液中Cr6+的性能研究

研究了无机、有机和无机-有机柱撑膨润土对水中C r6 的吸附去除性能。结果表明:三种柱撑膨润土对C r6 的去除效果明显高于膨润土原土,当投土量为8 g/L时,对C r6 的吸附去除率分别为81.03%、95.41%和85.11%;三种柱撑膨润土对C r6 的吸附在60 m in达到平衡;溶液pH对C r6 的去除有一定的影响,在酸性条件下的去除率略大于中性和碱性;温度升高,C r6 的去除率略有下降。     

聚丙烯酸-丙烯酸钠钙基复合膨润土的制备及其对铅和氟离子的吸附

以钙基膨润土为主要原料,部分中和的丙烯酸为聚合单体,采用水溶液聚合法,制备了膨润土与未中和丙烯酸单体的质量比例为8:2的聚丙烯酸-丙烯酸钠钙基复合膨润土,并对其进行表征. 结果表明,单体插层在膨润土层间发生聚合反应,但未破坏钙基膨润土的片层结构. 复合膨润土产品对铅离子和氟离子具有良好的吸附和再生性能,吸附量优于钙基膨润土和文献报道的其他改性膨润土;0.5 g复合膨润土处理50 mL浓度为80 mg/L的Pb2+溶液和16.104 mg/L的F-溶液时,平衡吸附量和去除率分别为6.70 mg/g, 83.69%和1.01 mg/g, 62.95%. 复合膨润土对Pb2+和F-的平衡吸附分别符合Langmuir和Freundlich等温吸附方程.     

Adsorption Behaviour of Ethylene Vinyl Acetate and Polycaprolactone-Bentonite Composites for Pb2+ Uptake

The results presented in this work show that the hydrophobic thermoplastics, namely ethylene vinyl acetate (EVA) and polycaprolactone (PCL), could be good matrices for the synthesis of polymer/bentonite composites via the melt-blending method for the removal of heavy metals from water. The hydrophobic nature of the polymers was countered by using dry Na₂SO₄ to form large free-volume pores. These pores, formed after the removal of the Na₂SO₄ by washing, improved the contact ratio between bentonite particles and Pb²⁺ ions. The composites were able to achieve up to 78% Pb²⁺ removal at an initial concentration of 200 mg/L in 10 h with a clay loading of 3% (w/w). The results confirmed that the PCL/bentonite composite was more effective and efficient in the adsorption of Pb²⁺ than the EVA/bentonite composite. The experimental data for both composites followed Langmuir and Freundlich models. The uptake of Pb²⁺ was found to be a result of a chemical interaction between the heavy metal, silanol (Si–OH) and aluminol (Al–OH) groups. The adsorption of Pb²⁺ onto the composites was found to follow pseudo-first-order kinetics and the results supported a monomolecular reaction mechanism.     

Response surface modeling,isotherm, thermodynamic and optimization study of arsenic (V) removal from aqueous solutions using modified bentonite-chitosan (MBC)

Arsenic contamination, a worldwide concern, has received a great deal of attention due to its toxicity and carcinogenicity. In the present study, we focused on the combined application of modified bentonite and chitosan (MBC) for the removal of As(V). Arsenic removal experiments were carried out to determine the amount of As(V) adsorbed as a function of pH (2-8), sorbent dosage (0.1-1.5 g/L), As(V) concentration (20-200mg/L) and time (60-240 min). The system was optimized by means of response surface methodology. The analysis of variance (ANOVA) of the quadratic model demonstrated that the model was highly significant (R²≈97.3%). Optimized values of pH, sorbent dosage, initial As(V) concentration and time were found to be 3.7, 1.40 g/L, 69mg/L, and 167min, respectively. The results reveal that the prepared adsorbent has a high adsorption capacity (122.23mg/g) for As(V) removal. Among the isotherm models used, the Langmuir isotherm model was the best fit for the obtained data. The adsorption kinetics following a pseudo-second-order kinetic model was involved in the adsorption process of As(V). Thermodynamic studies confirmed the spontaneous and endothermic character of adsorption process.     

Removal of Humic Acid Using PEI‐Modified Fungal Biomass

Abstract

A modified fungal biomass was prepared through the adsorption of polyethylenimine (PEI) and subsequent crosslinking with glutaraldehyde on the biomass surface. FTIR result verified that the amine groups were introduced on the biomass surface. As a large number of amine groups are present on the biomass surface and can be protonated in solution, the modified biomass was positively charged at pH<10.3. The modified biomass was used as an adsorbent to remove humic acid in a series of batch adsorption experiments. The amount of humic acid adsorbed on the biosorbent decreased with increasing solution pH, and the electrostatic interaction between the positive protonated amine groups on the biomass surface and the negative carboxyl groups in the humic acid molecules played an important role in humic acid adsorption. The time‐dependent sorption of humic acid on the biomass can be described well by the Fickian diffusion model at the initial stage and the pseudo‐second‐order equation over 10 h. Using the Langmuir adsorption isotherm, the maximum sorption capacity of the modified biomass for humic acid at pH 5 was 96.5 mg/g. The desorption experiments showed that the humic acid loaded biomass could be easily regenerated in a 0.1 M NaOH solution, and the regenerated biomass possessed good adsorption capacity up to the fifth cycle. The PEI‐modified biomass with polyamine chains shows the potential for application in water treatment for the removal of humic substances.     

Removal of humic acid from water using adsorption coupled with electrochemical regeneration

A novel and economic waste water treatment technology comprised of adsorption coupled with electrochemical regeneration was introduced at the University of Manchester in 2006. An electrically conducting adsorbent material called Nyex? 1000 (Graphite intercalation based material) was developed for the said purpose. This adsorbent material delivered significantly lower adsorption capacity for the removal of a number of organic pollutants. With the aim to expand the scope of newly developed adsorbent material called Nyex? 2000, we studied the adsorption of humic acid followed by electrochemical regeneration. Nyex? 2000 is a highly electrically conducting material with an adsorption capacity almost twice that of Nyex? 1000 (intercalation based graphite compound) for humic acid. The adsorption of humic acid onto both Nyex? adsorbents was found to be fast enough keeping almost the same kinetics with approximately 50% of the adsorption capacity being achieved within the first twenty minutes. The parameters affecting the regeneration efficiency, including the treatment time, charge passed and current density, were investigated. The regeneration efficiency at around 100% for Nyex? 1000 & 2000 adsorbents saturated with humic acid was obtained using the charge passed of 8 and 22 Cg^?1 at a current density of 7mA cm^?2 during a treatment time of 30minutes, respectively.     

两种不同柱撑膨润土对溴离子的去除研究

以钙基膨润土为原料,通过柱撑改性制得两种不同的改性膨润土-铁柱撑膨润土和铝柱撑膨润土。两种膨润土分别应用于溴离子的去除当中。结果表明,两种鹏润如对溴离子的去除效果相差不大。以投加量为0.5 g为例,反应进行20 min时,溴离子的去除率已达到平衡时的90%以上。随着温度由10℃上升到45℃,铝柱撑膨润土和铁柱撑膨润土对溴离子的去除率分别由86.5%和91.7%下降到56.1%和49.6%。随着pH的升高,溴离子的去除率要显著的降低,实验条件下,选取pH 6时,效果最佳。通过吸附动力学和等温线的分析,可知改性膨润土对溴离子的吸附属于自发的放热的过程。     

乙酸膨润土对孔雀石绿的吸附去除

为提高膨润土对染料的吸附性能,制备了有机酸改性膨润土-乙酸膨润土(AAB).对AAB 进行了N₂-BET、FTIR 和XRD 表征分析,同时考察了影响乙酸膨润土(AAB)去除孔雀石绿(MG)的主要因素,并进行了吸附 动力学和吸附等温模型研究。研究结果表明,乙酸分子已成功负载在天然膨润土(RB)上,AAB 的比表面积为 45m2/g;层间距为1.721nm;在实验条件下,用0.4g/L 的吸附剂处理300mg/L 的MG,MG 的脱色率达到99%; pH 值为1～12 时,AAB 对MG 的脱色率均达到97%以上;低浓度的十二烷基苯磺酸钠(SDBS)能提高AAB 对MG 的去除率,而加入十六烷基三甲基溴化铵(CTAB)会产生很强的抑制作用;AAB 对MG 的吸附符合 Langmuir 模型,Langmuir 吸附容量高达1250mg/g;MG 在AAB 上的吸附先是一个快速吸附阶段,然后逐渐到 达吸附平衡,符合准二级动力学模型。总之,AAB 环保无毒,在MG 去除方面具有用量低、适应pH 值范围广、吸附容量大和吸附快速的优势。     

Application of ultrafiltration membranes for removal of humic acid from drinking water

Humic acids are primarily a result of the microbiological degradation of surrounding vegetation and animal decay and enter surface waters through rain water run-off from the surrounding land. This often gives rise to large seasonal variations, high concentrations in the wet season and lower concentrations in the dry season. Alone humic acid is just a colour problem but when present in conventional treatment processes like chlorination, carcinogenic by-products like trihalomethane and haloacetic acid are formed. This, in addition to the demand for clean potable drinking water, has sparked extensive research into alternative processes for the production of drinking water from various natural/industrial sources. One of the major areas of focus in these studies is the use of membranes in microfiltration, ultrafiltration and nanofiltration. In this report the humic acid removal efficiency of ultrafiltration membranes with 3 kDa, 5 kDa and 10 kDa MWCO is examined. The membranes were made of regenerated cellulose and were in the form of cassette providing a 0.1 m² surface area. At first distilled and deionised water, known as milliQ water, was used as the background feed solution to which humic acid powder was added. It was found that all three membranes removed humic acid with an efficiency of approx. 90% and were capable of reducing initial concentrations of 15mg/L to below the New Zealand regulatory limit of 1.17 mg/L. The permeate flux at a transmembrane pressure of 2.1 bar was approx. 20 l/m²/h (LMH) and 40 LMH, respectively through the membranes with MWCO 3 kDa and 5 kDa. These membranes experienced significant surface fouling resulting in retentate flow rates as low as 11 litres per hour after just four runs compared to the recommended 60–90 l/h. Cleaning with 0.1 M NaOH slightly improved the retentate flow rate, but well below those obtained with fresh membranes. The 10 kDa membrane provided high retentate flow rates which evidently minimised fouling by providing a good sweeping action across the membrane surface while maintaining humic acid removal below the regulatory 1.17 mg/L level. The permeate flux through this membrane was initially high (140–180 LMH) and reduced to approx. 100 LMH after 10–12 min of operation. Increasing the initial humic acid feed concentration from 10 mg/L to 50 mg/L did not significantly decrease humic acid removal efficiency although the retentate flow rate was lower at higher concentrations. Finally the tap water was tested as the background solution and treated for the removal of humic acid. The presence of ions and other impurities in the tap water had little effect on humic acid removal. However, the permeate flux through 10 kDa membrane decreased from 100 LMH for milliQ water to 60 LMH for tap water after 20 min of operation.     

One-step hydrothermal synthesis of a green NiCo-LDHs-rGO composite for the treatment of lead ion in aqueous solutions

Herein, we have synthesized a microspherical nickel-cobalt-layered double hydroxides-reduced graphene oxide composite (NiCo-LDHs-rGO) through a one-step hydrothermal method and then used it as an adsorbent for the removal of Pb²⁺ from aqueous solutions. Fourier transform infrared spectrophotometry (FT-IR), field emission scanning electron microscopy (FESEM), mapping elemental analysis, electron dispersive x-ray spectroscopy (EDX), x-ray diffraction analysis (XRD), and the Brunauer–Emmett–Teller (BET) method were used for the characterization of the adsorbent. Factors affecting the adsorption of Pb²⁺ ion such as solution pH, adsorbent dosage, contact time, competing ion, and regeneration were investigated in batch mode by the NiCo-LDHs-rGO. Under optimized conditions based on the Taguchi method (pH = 5.0, adsorbent dosage = 20 mg, and contact time = 30 min), the highest removal percentage was found to be 99.7% for 100 mg L⁻¹ of Pb²⁺. According to the results, NiCo-LDHs-rGO exhibited a high preference for Pb²⁺ over Cu²⁺, Zn²⁺, and Cd²⁺. This adsorbent was regenerated for several cycles (using 0.01 M HCl) with no significant deterioration in performance. Analyses of the adsorption isotherm models revealed that the adsorption of Pb²⁺ follows Freundlich isotherm with a maximum adsorption capacity of 200 mg g⁻¹. Also, the kinetic data confirmed that pseudo second order kinetic equation is the best model for predicting the kinetics. Furthermore, the Simulink modelling illustrated that the adsorption kinetics of Pb²⁺ onto NiCo-LDHs-rGO is done with high accuracy in a continuous stirred-tank reactor. Finally, dual interactions of the effective parameters can be modelled by polynomial equations in MATLAB, and according to the Taguchi model, pH is clearly the most important feature among all effective parameters.     

Ability of iron(III)‐loaded carboxylated polyacrylamide‐grafted sawdust to remove phosphate ions from aqueous solution and fertilizer industry wastewater: Adsorption kinetics and isotherm studies

Iron(III)‐loaded carboxylated polyacrylamide‐grafted sawdust was investigated as an adsorbent for the removal of phosphate from water and wastewater. The carboxylated polyacrylamide‐grafted sawdust was prepared by graft copolymerization of acrylamide and N,N′‐methylenebisacrylamide onto sawdust in the presence of an initiator, potassium peroxydisulfate. Iron(III) was strongly attached to the carboxylic acid moiety of the adsorbent. The adsorbent material exhibits a very high adsorption potential for phosphate ions. The coordinated unsaturated sites of the iron(III) complex of polymerized sawdust were considered to be the adsorption sites for phosphate ions, the predominating species being H₂PO ions. Maximum removal of 97.6 and 90.3% with 2 g L^?1 of the adsorbent was observed at pH 2.5 for an initial phosphate concentration of 100 and 250 μmol L^?1, respectively. The adsorption process follows second‐order kinetics. Adsorption rate constants as a function of concentration and temperature and kinetic parameters, such as ΔG^±, ΔH^±, and ΔS^±, were calculated to predict the nature of adsorption. The L‐type adsorption isotherm obtained in the sorbent indicated a favorable process and fitted the Langmuir equation model well. The adsorption capacity calculated by the Langmuir adsorption isotherm gave 3.03 × 10^?4 mol g^?1 of phosphate removal at 30°C and pH 2.5. The isosteric heat of adsorption was also determined at various surface loadings of the adsorbent. The adsorption efficiency toward phosphate removal was tested using industrial wastewater. Different reagents were tested for extracting phosphate ions from the spent adsorbent. About 98.2% of phosphate can be recovered from the adsorbent using 0.1M NaOH. Alkali regeneration was tried for several cycles with a view to recover the adsorbed phosphate and also to restore the adsorbent to its original state. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2541–2553, 2002