Application of chitosan-coated quartz sand for Congo red adsorption from aqueous solution

The preparation, characterization, and environmental application of chitosan-coated quartz sand for Congo red adsorption have been investigated. The absorbent was characterized by Fourier transform infrared spectrophotometer (FTIR) and scanning electron microscope (SEM). The experiments were carried out in a batch system to optimize operation variables: contact time, Congo red concentration, absorbent dosage, temperature, and pH. The optimum conditions for Congo red adsorption were pH 5, 45°C and contact time of 4 h. An amount of 1 g of chitosan-coated quartz sand could successfully remove 96% of the dye form 50 mg/L Congo red solution. The adsorption kinetics and equilibrium isotherms showed that the sorption processes were better fitted by pseudo-second order equation and Langmuir equation, respectively. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

糠醛渣对刚果红的吸附性能研究

研究糠醛渣对染料的静态吸附.以刚果红染料为例,研究了糠醛渣对染料废水的吸附特性,考察了振荡时间、温度、吸附剂粒度和吸附剂剂量对糠醛渣吸附刚果红的影响,测试了吸附等温曲线.随着接触时间的延长,糠醛渣对亚甲基监的脱色率增加,60min后,吸附作用基本达到平衡.随着温度的升高,脱色率增加,糠醛渣对亚甲基蓝的吸附是吸热反应.随着粒度的增加,脱色率呈上升趋势.当糠醛渣剂量为0.6g时,其对亚甲基蓝的脱色率达90.72%.糠醛渣作为吸附剂处理含刚果红废水,是一种有效的方法.该方法实现了以废治废的废物资源化目标,具有良好的社会效益和经济效益.     

A new application of Hydroxyapatite extracted from dromedary bone: Adsorptive removal of Congo red from aqueous solution

The aim of this paper is to evaluate the efficiency of the natural hydroxyapatite powder for anionic dye (Congo red) elimination from water and optimization of adsorption process parameters that are contact time (0-360 min), solution pH (4-9), initial dye concentration (400-2400 mg/l), and adsorbent dosage (0.4-20 g/l). Natural hydroxyapatite with high surface area was prepared from animal agriculture waste dromedary bone. X-ray diffraction, transmission electron microscopy, transform infrared spectroscopy, and elemental analysis characterizations of the powder prepared show a hexagonal structure, the irregular form of hydroxyapatite and presence of other elements as trace element. The results of adsorption tests demonstrated the high efficiency of natural hydroxyapatite for removal of Congo red from water solution whose maximum experimental capacity adsorption of Congo red by natural hydroxyapatite is 900 mg/g at pH 4.5, equilibrium time 240 min and adsorbent dosage 2 g/l. According to the correlation coefficient value, the pseudo-second order kinetic model identified the sorption mechanism of pollutant used on natural hydroxyapatite. The Freundlich isotherm is the best representative theoretical model of the dye molecules’ adsorption on the natural hydroxyapatite support.     

Removal of Congo red from aqueous solution using a chitosan/organo‐ montmorillonite nanocomposite

To further improve the adsorption capacity of chitosan (CTS), a series of novel chitosan/organo‐montmorillonite nanocomposites (CTS/OMMT) were synthesized and the adsorption abilities for Congo red (CR) investigated in this study. The nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction analysis (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the results indicated that an exfoliated nanostructure was formed in CTS/OMMT nanocomposites. Compared with the adsorption capacity of OMMT (192.4 mg g^?1), CTS/OMMT with an amount of cetyltrimethylammonium bromide equal to 0.75 CEC of MMT and molar ratio of CTS to OMMT of 1:10 exhibited the higher adsorption capacity (290.8 mg g^?1). The adsorption behaviours of OMMT and CTS/OMMT showed that the adsorption kinetics and isotherms were in good agreement with a pseudo‐second‐order equation and the Langmuir equation, respectively. The IR spectra revealed that a chemical interaction occurred between CTS/OMMT and CR. The adsorption capacity of CTS/OMMT nanocomposite was higher than that of other absorbents; this study suggested that the CTS/OMMT nanocomposite could be used as an adsorbent to remove CR dye from aqueous solution. Copyright © 2007 Society of Chemical Industry     

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.     

MXene@CS复合絮凝剂的制备及其对刚果红去除的研究

壳聚糖（CS）因具有大量的羟基和氨基,可为吸附色素污染物提供较多活性位点,但其在酸性条件易于溶解。MXene可为CS提供支撑位点,从而构建新型MXene@CS复合材料。研究构建了新型Ti₃C₂T_X@CS有机无机复合材料,并应用于刚果红的去除研究。通过对Ti₃C₂T_X@CS的微观形貌、晶体结构、表面官能团等进行表征分析,发现Ti₃C₂T_X@CS的复合过程为物理复合。絮凝实验结果表明：在Ti₃C₂T_X@CS投加量为30 mg、溶液pH为9、反应时间为30 min、温度为25~60 ℃条件下,Ti₃C₂T_X@CS对50 mL质量浓度为500 mg/L刚果红（CR）溶液的脱色率达到99%以上。通过实验结果和反应前后Ti₃C₂T_X@CS电位变化推断,Ti₃C₂T_X@CS对刚果红的去除机理主要是电中和作用和吸附架桥作用。     

Adsorption of Congo Red from Aqueous Solutions Using Chitosan Hydrogel Beads Formed by Various Anionic Surfactants

The structural organization of chitosan hydrogel beads (CSBs) formed by various anionic surfactants, sodium dodecyl sulfate (SDS), sodium decyl sulfate (DS), dodecyl benzenesulfonic acid sodium salt (SDBS), and dioctyl sulfosuccinate sodium salt (DSS), and their applications as adsorbents for environmental purifications were investigated using Congo red (CR) as a model dye. The adsorption capacities of CSB as a function of surfactant concentration revealed that CSBs formed by 5 g/L anionic surfactant were the most effective for CR adsorption. The structure of CSBs and their adsorption capacities for CR depend on the nature of anionic surfactants. The maximum adsorption capacities of CSB_SDS, CSB_DS, CSB_SDBS, and CSB_DSS obtained from the Langmuir isotherm model were 186.02, 209.28, 207.25, and 113.83 mg/g, respectively, indicating that CSB_DS was the best adsorbent for CR.     

Adsorption Characteristics of Congo Red from Aqueous Solution onto Tea Waste

The feasibility of using tea waste (TW) as a low-cost adsorbent for the adsorption of an anionic dye (Congo red) from aqueous solution has been investigated. Adsorption in a batch process was conducted to study the effect of adsorbent dosage, initial dye concentration, contact time, pH, and temperature. The experimental data were analyzed by the Langmuir, Freundlich, and Temkin models. The adsorption system was best described by the Langmuir isotherm (R ² > 0.99). Adsorption kinetics followed a pseudo-second-order model (R ² > 0.99). The effect of mechanical treatment (vibratory mill) was also studied. The experimental results showed that using this physical treatment leads to an increase in the adsorption capacity of TW from 32.26 to 43.48 mg/g. Thermodynamic analyses revealed that the adsorption of Congo red on TW was endothermic and spontaneous in nature. The results indicated that TW can be employed as a potential low-cost adsorbent for the removal of Congo red from aqueous solution.     

Adsorption of congo red by three Australian kaolins

This study investigated the potential use of kaolin as alternative adsorbents for removal of congo red from wastewater. The effect of adsorbent dosage, dye concentration, pH and temperature were experimentally studied to evaluate the adsorption capacity, kinetics and equilibrium. Experimental results revealed that optimal adsorption took place at acidic pH and high dye concentration. Ceram kaolin had the highest removal efficiency among studied kaolins, followed by K15GR and Q38. The dye uptake process obeyed the pseudo-second order kinetic expression and was best described by the Langmuir isotherm. Intra-particle diffusion studies showed that the adsorption mechanism was not exclusively controlled by the diffusion step and was more likely to be governed by external mass transfer. Thermodynamic studies showed congo red adsorption on all kaolins was exothermic and spontaneous in nature. Recovered Q38 and K15GR kaolin demonstrated an enhanced adsorption capability. The results indicate that these local kaolins could be employed as low-cost alternatives for removal of anionic dyes from industrial wastewater.     

多孔二氧化钛吸附刚果红

以异丙醇钛为前体,十二烷胺为模板剂,采用配体辅助模板法合成高比表面积多孔二氧化钛材料,利用氮气吸附对其孔径性质进行分析。通过静态吸附实验研究了多孔二氧化钛对刚果红的吸附行为,考察了吸附时间、温度、搅拌速度、吸附剂用量和初始浓度对刚果红吸附效果的影响。分别在相关条件下,结果表明：当吸附时间为30min时,脱除率达98%以上;吸附温度为45℃时,脱除率可达98%;摇床转速为160r/min时,脱除率达到最大;当吸附剂使用量为0.10g时,脱除率能够达到98%左右,已能够满足应用要求;多孔二氧化钛吸附刚果红的吸附量与刚果红初始浓度成正比。     

碱性钙基膨润土对亚甲基蓝和刚果红的吸附去除

该文研究了碱性钙基膨润土(ACB)对水体中的亚甲基蓝(MB)和刚果红(CR)染料的吸附性能,考察了吸附剂用量、吸附时间及温度、pH及盐等因素对吸附效果的影响,同时进行了两种染料在碱性钙基膨润土上的吸附等温模型、吸附动力学模型研究。结果表明,ACB对MB、CR的脱色率随着吸附剂用量的增加而增加,在实验条件下,50 mg/L MB和100 mg/L CR的最佳吸附剂质量浓度分别为1.0 g/L和2.0 g/L;升高温度可以加快吸附速率,但对最终的脱色率影响很小;50 mg/L MB的吸附平衡时间在60 min左右,100 mg/L CR的吸附平衡时间在120 min左右;在pH=3～12时,ACB对MB的脱色率都稳定在99%左右,而适宜ACB吸附CR的pH=3～7,对CR的脱色率保持在90%左右;NaCl的加入对MB的吸附效果影响很小,对CR的吸附则有很强的抑制作用;ACB对MB的吸附同时符合Langmuir和Freundlich模型,而ACB对CR的吸附则更符合Langmuir模型;ACB对两种染料的吸附过程均符合准二级动力学模型,颗粒内扩散模型的拟合结果说明吸附过程存在颗粒内扩散作用。     

Adsorption of Congo Red from Aqueous Solution on Surfactant-Modified Zeolites with Different Coverage Types: Behavior and Mechanism

A series of surfactant-modified zeolites (SMZs) were prepared by loading various amounts of cetylpyridinium bromide (CPB) onto the external surface of natural zeolites, and their CPB coverage types were determined by comparing the loading amounts of cetylpyridinium (CP⁺) and bromide (Br^?). The behavior and mechanism of Congo red (CR) adsorption onto SMZs with different coverage types were investigated. The SMZ was effective for the removal of CR from aqueous solution. The SMZ with higher CP⁺ loading amount exhibited higher CR adsorption capacity. The amount of CR adsorbed on SMZ was found to increase with an increase in contact time and initial dye concentration but was found to decrease with increasing adsorbent dosage. Coexisting Cu(II) in solution favored CR adsorption onto SMZs. The kinetic data of CR on SMZs followed a pseudo-second-order model. The equilibrium adsorption data of CR on SMZs were well described by the Langmuir isotherm model. For SMZ with monolayer coverage, hydrophobic interaction was the main mechanism for CR adsorption. For SMZ with bilayer coverage, anion exchange, and organic partitioning were the main mechanisms for CR adsorption. For SMZ with patchy bilayer coverage, anion exchange, organic partitioning and hydrophobic interaction were the main mechanisms for CR adsorption.     

基于响应曲面法的磁性离子交换树脂去除甲基橙和刚果红的优化

选取树脂用量、溶液初始pH值、吸附质浓度和吸附时间四个因素,用Box-Behnken响应曲面法分别建立了甲基橙和刚果红在磁性离子交换(MIEX)树脂上吸附的二次多项式回归模型,使用方差及显著性分析证明了回归方程的可靠性。优化了MIEX树脂去除甲基橙和刚果红的工艺参数,探究了最佳工艺条件下MIEX树脂对甲基橙(刚果红)的去除效果。使用NaCl再生饱和吸附后的MIEX树脂,用扫描电镜对吸附前后的树脂进行表征。结果表明,在最优工艺条件下,MIEX树脂对甲基橙和刚果红的去除率最高可达99.12%和98.29%。溶液初始pH值和树脂用量之间的交互作用对MIEX树脂去除甲基橙和刚果红有显著影响。NaCl溶液对MIEX树脂的再生效果显著。     

Removal of Congo Red dye from aqueous solution using Amberlite IRA-400 in batch and fixed bed reactors

Removal of Congo Red (CR) azo dye by adsorption process using Amberlite IRA-400 resin was evaluated in both batch and fixed bed system. From the batch adsorption results, maximum loading efficiency (99.99%) of CR dye was obtained at the conditions pH 4.5, temp. 303?K, contact time 180?min., Amberlite IRA-400 dose 0.5?g. The isotherm study ascertained on favorability of adsorption process as the value of separation factor (K_L?=?0.88) and Freundlich constant (1/n?=?0.96?R²?=?0.99) than Freundlich model (R²?=?0.97). The kinetic data studied at three different CR dye concentration (50, 75, 100?mg) and results were fitted with both pseudo-first-order and second-order model equations. The values of R² obtained are of 0.95 and 0.99 for former and later one, respectively, ensuring on best fitting of pseudo-second-order kinetics and also suggesting about the chemisorptions type of adsorption. The bed depth service model was applied for competitive analysis of the CR dye adsorption in column variables indicating mass transfer from aqueous solution to Amberlite IRA-400 phase. Fourier transform infrared analysis of CR-loaded resin Amberlite IRA-400 showed a band shifted from 1057 to 1130?cm^?1 confirming CR adsorption with Amberlite IRA-400. Scanning electron microscope analysis of resin before and after adsorption was well evident from the phase patterns. Selective separation of CR dye from waste effluent of a textile industry bearing CR dye along with other trace heavy metal was achieved.     

CTAB改性沸石对刚果红的吸附

为有效去除水溶液中的刚果红染料，采用阳离子表面活性剂十六烷基三甲基澳化铵（CRAB）对沸石进行改性。刚果红在改性沸石上的吸附量远远大于未改性沸石的吸附量。考察了吸附时间、溶液pH值、离子强度等因素对改性沸石吸附效果的影响。通过对吸附等温线进行分析，沸石对刚果红的吸附很好的符合Lansmuir吸附模型。     

Hierarchical porous MgBO2(OH) microspheres:Hydrothermal synthesis,thermal decomposition,and application as adsorbents for Congo red removal

A facile eco-friendly hydrothermal route(180 °C, 12.0 h) has been developed for the first time to the uniform hierarchical porous MgBO_2(OH) microspheres without the aid of any organic additive, surfactant or template, by using the abundant MgCl_2·6 H_2 O, H_3BO_3 and NaOH as the raw materials. The as-obtained porous microspheres exhibit a specific surface area of 94.752 mg·g~(-1), pore volume of 0.814 cm3·g~(-1), and ca. 84.0% of which have a diameter of 2.25–3.40 μm. The thermal decomposition of the porous MgBO_2(OH) microspheres(650 °C,2.5 °C·min~(-1)) leads to the porous Mg_2B_2O_5 microspheres with well-retained morphology. When utilized as the adsorbents for the removal of CR from mimic waste water, the present porous MgBO_2(OH) microspheres exhibit satisfactory adsorption capacity, with the maximum adsorption capacity q~(-1) mof 309.1 mg·g, much higher than that derived from most of the referenced adsorbents. This opens a new window for the facile green hydrothermal synthesis of the hierarchical porous MgBO_2(OH) microspheres, and extends the potential application of the 3 D hierarchical porous metal borates as high-efficiency adsorbents for organic dyes removal.     

Adsorption behavior of estrogenic compounds on carbon nanotubes from aqueous solutions: Kinetic and thermodynamic studies

In this study different estrogenic compounds, estrone (E1), 17β-estradiol (E2), and 17a-ethinylestradiol (EE2), were removed from the model and real solution by the newly emerged multi-walled carbon nanotubes. The effects of different factors which affect the removal process were studied and optimized for efficient removal. The kinetics of E1, E2, and EE2 adsorption on MWCNTs were analyzed using different kinetic models and the results showed that the removal was mainly a pseudo-second-order process. The thermodynamic study showed the spontaneity and exothermic nature of the removal process, with negative entropy.     

水热法制备TiO_2/MMT复合材料及其吸附性能研究

以碳酸钠改性后的钠基蒙脱土为载体、硫酸钛为钛源,采用水热法制备了TiO_2/蒙脱土复合材料。通过XRD、SEM和N_2吸附-脱附测试手段研究其微观结构和光谱学性能,并以刚果红溶液为模拟染料废水,研究其吸附性能。结果表明,TiO_2附着于蒙脱土表面,形成TiO_2/蒙脱土复合材料。该材料具有介孔结构,比表面积高达261.03m~2/g,在刚果红初始浓度为50mg/L、振荡时间为2h的条件下,TiO_2/蒙脱土对刚果红的吸附率为88.96%,极限吸附量可达344.8mg/g。     

Adsorption of cadmium(II) from aqueous solution by surface oxidized carbon nanotubes

Carbon nanotubes (CNTs) were oxidized with H₂O₂, KMnO₄ and HNO₃. Their physicochemical properties were investigated by BET N₂ adsorption, laser particle examination, Boehm’s titration, zeta potential measurement and cadmium(II) adsorption. The experimental results suggest that cadmium(II) adsorption capacities for three kinds of oxidized CNTs increase due to the functional groups introduced by oxidation compared with the as-grown CNTs. The cadmium(II) adsorption capacity of the as-grown CNTs is only 1.1 mg g⁻¹, while it reaches 2.6, 5.1 and 11.0 mg g⁻¹ for the H₂O₂, HNO₃ and KMnO₄ oxidized CNTs, respectively, at the cadmium(II) equilibrium concentration of 4 mg l⁻¹. Adsorption of cadmium(II) by CNTs was strongly pH-dependent and the increase of adsorption capacities for HNO₃ and KMnO₄ oxidized CNTs is more obvious than that of the as-grown and H₂O₂ oxidized CNTs at lower pH regions. The experiments of CNT dosage effect on the cadmium(II) adsorption show that the adsorption capacity for KMnO₄ oxidized CNTs has a sharper increase at the CNT dosage from 0.03 to 0.08 g per 100 ml than the as-grown, H₂O₂ and HNO₃ oxidized CNTs and its removal efficiency almost reaches 100% at CNT dosage of 0.08 g per 100 ml. Analysis revealed that the KMnO₄ oxidized CNTs hosted manganese residuals, and these surely contributed to cadmium sorption to a yet-undefined extent.     

Adsorption of cadmium from aqueous solution by phosphogypsum

In the present study, the adsorption of cadmium on phosphogypsum, a waste material from the manufacture of phosphoric acid by wet process, was studied. Before batch adsorption study, phosphogypsum was pre-conditioned by milk of lime. Effect of initial pH on cadmium adsorption was investigated. It was found that cadmium adsorption was dependent on solution pH and maximum cadmium removal was observed in the pH range of 9.5 and 11.5. The Langmuir and Freundlich theories were used to describe the cadmium adsorption process, and the Freundlich isotherm showed the best fit to the process. Maximum adsorption capacity of lime-preconditioned phosphogypsum was found to be 131.58 mg/g.