Cadmium sorption by sodium and thiourea-modified zeolite-rich tuffs

In the present investigation, two zeolite-rich tuffs from Guaymas and El Cajon(State of Sonora), which were conditioned with a sodium chloride solution and subsequently modified with a thiourea solution, were chosen to evaluate the removal of Cd from aqueous systems. The zeolitic materials were characterized by scanning electron microscopy and X-ray diffraction. The surface area was also determined. The experiments were performed in a batch system, and the influences of p H, contact time between phases, and the concentration of Cd in the solution on the adsorption by sodium or thiourea-modified zeolite-rich tuff were investigated. It was found that the efficiency of Cd ion removal from aqueous solutions is influenced by the p H of the aqueous systems. The Cd adsorption kinetic data were well fitted to a pseudo-second-order model in all cases. The Langmuir and Langmuir–Freundlich isotherms adequately described the Cd sorption behavior by the zeolite from El Cajon pretreated with Na Cl and the zeolite from Guaymas modified with thiourea, respectively.     

Adsorption characteristics of humic acid-immobilized amine modified polyacrylamide/bentonite composite for cationic dyes in aqueous solutions

Humic acid-immobilized amine modified polyacrylamide/bentonite composite (HA-Am-PAA-B) was prepared and used as an adsorbent for the adsorption of cationic dyes (Malachite Green (MG), Methylene Blue (MB) and Crystal Violet (CV)) from aqueous solutions. The polyacrylamide/bentonite composite (PAA-B) was prepared by intercalative polymerization of acrylamide with Nabentonite in the presence of N,N0-methylenebisacrylamide as a crosslinking agent and hexamethylenediammine as propagater. PAA-B was subsequently treated with ethylenediammine to increase its loading capacity for HA. The surface characterizations of the adsorbent were investigated. The adsorbent behaved like a cation exchanger and more than 99.0% removal of dyes was detected at pH range 6.0–8.0. The capacity of HA-Am-PAA-B was found to decrease in the following order: MG > MB > CV. The kinetic and isotherm data were interpreted by pseudo-second order rate equation and Freundlich isotherm model, respectively. Experiments were carried out using binary solute systems to assess the competitive adsorption phenomenon. The experimental isotherm data for each binary solute combination of MG, MB and CV were analyzed using Sheindrof-Rebhun-Sheintuch (SRS) (multicomponent Freundlich type) equation.     

Kinetics and isotherms of Neutral Red adsorption on peanut husk

Adsorption of Neutral Red (NR) onto peanut husk in aqueous solutions was investigated at 295 K. Experiments were carried out as function of pH, adsorbent dosage, contact time, and initial concentration. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Toth isotherm models. The results indicated that the Toth and Langmuir models provided the best correlation of the experimental data. The adsorption capacity of peanut husk for the removal of NR was deter...     

Removal of tetracycline from aqueous solution by a Fe3O4 incorporated PAN electrospun nanofiber mat

Pollution of antibiotics, a type of emerging contaminant, has become an issue of concern,due to their overuse in human and veterinary application, persistence in environment and great potential risk to human and animal health even at trace level. In this work, a novel adsorbent, Fe3O4 incorporated polyacrylonitrile nanofiber mat(Fe-NFM), was successfully fabricated via electrospinning and solvothermal method, targeting to remove tetracycline(TC), a typical class of antibiotics, from aqueous solution. Field emission scanning electron microscopy and X-ray diffraction spectroscopy were used to characterize the surface morphology and crystal structure of the Fe-NFM, and demonstrated that Fe-NFM was composed of continuous, randomly distributed uniform nanofibers with surface coating of Fe3O4 nanoparticles. A series of adsorption experiments were carried out to evaluate the removal efficiency of TC by the Fe-NFM. The pseudo-second-order kinetics model fitted better with the experimental data. The highest adsorption capacity was observed at initial solution p H 4 while relative high adsorption performance was obtained from initial solution p H 4 to 10. The adsorption of TC on Fe-NFM was a combination effect of both electrostatic interaction and complexation between TC and Fe-NFM. Freundlich isotherm model could better describe the adsorption isotherm. The maximum adsorption capacity calculated from Langmuir isotherm model was 315.31 mg/g. Compared to conventional nanoparticle adsorbents which have difficulties in downstream separation, the novel nanofiber mat can be simply installed as a modular compartment and easily separated from the aqueous medium, promising its huge potential in drinking and wastewater treatment for micro-pollutant removal.     

Activated carbons derived from oil palm empty-fruit bunches： Application to environmental problems

Activated carbons derived from oil palm empty fruit bunches （EFB） were investigated to find the suitability of its application for removal of phenol in aqueous solution through adsorption process, Two types of activation namely; thermal activation at 300, 500 and 800℃and physical activation at 150℃ （boiling treatment） were used for the production of the activated carbons. A control （untreated EFB） was used to compare the adsorption capacity of the activated carbons produced from these processes. The results indicated that the activated carbon derived at the temperature of 800℃ showed maximum absorption capacity in the aqueous solution of phenol. Batch adsorption studies showed an equilibrium time of 6 h for the activated carbon at 800℃. It was observed that the adsorption capacity was higher at lower values of pH （2-3） and higher value of initial concentration of phenol （200-300 mg/L）. The equilibrium data fitted better with the Freundlich adsorption isotherm compared to the Langmuir. Kinetic studies of phenol adsorption onto activated carbons were also studied to evaluate the adsorption rate. The estimated cost for production of activated carbon from EFB was shown in lower price （USD 0.50/kg of activated carbon） compared the activated carbon from other sources and processes.     

Statistical optimization of adsorption processes for removal of 2,4-dichlorophenol by activated carbon derived from oil palm empty fruit bunches

The adsorption capacity of activated carbon produced from oil palm empty fruit bunches through removal of 2,4-dichlorophenol from aqueous solution was carried out in the laboratory. The activated carbon was produced by thermal activation of activation time with 30 min at 800℃. The adsorption process conditions were determined with the statistical optimization followed by central composite design. A developed polynomial model for operating conditions of adsorption process indicated that the optimum conditions for maximum adsorption of phenolic compound were： agitation rate of 100 r/min, contact time of 8 h, initial adsorbate concentration of 250 mg/L and pH 4. Adsorption isotherms were conducted to evaluate biosorption process. Langmuir isotherm was more favorable （R^2=0.93） for removal of 2,4-dichlorophenol by the activated carbon rather than Freundlich isotherm （R^2=0.88）.     

Selective adsorption of silver ions from aqueous solution using polystyrene-supported trimercaptotriazine resin

Trimercaptotriazine-functionalized polystyrene chelating resin was prepared and employed for the adsorption of Ag(I) from aqueous solution. The adsorbent was characterized according to the following techniques: Fourier transform infrared spectroscopy, elemental analysis, scanning electron microscopy and the Brunauer-Emmet-Teller method. The effects of initial Ag(I) concentration, contact time, solution pH and coexisting ions on the adsorption capacity of Ag(I) were systematically investigated. The maximum adsorption capacity of Ag(I) was up to 187.1 mg/g resin at pH 0.0 and room temperature. The kinetic experiments indicated that the adsorption rate of Ag(I) onto the chelating resin was quite fast in the first 60 min and reached adsorption equilibrium after 360 min. The adsorption process can be well described by the pseudo second-order kinetic model and the equilibrium adsorption isotherm was closely fitted by the Langmuir model. Moreover, the chelating resin could selectively adsorb more Ag(I) ions than other heavy metal ions including: Cu(II), Zn(II), Ni(II), Pb(II) and Cr(III) during competitive adsorption in the binary metal species systems, which indicated that it was a highly selective adsorbent of Ag(I) from aqueous solution.     

Adsorption of naphthalene onto a high-surface-area carbon from waste ion exchange resin

A high-surface-area carbon (KC-1) was prepared from waste polystyrene-based ion exchange resin by KOH activation and used for naphthalene adsorption. The carbon exhibited a good hydrophobic nature with developed porous structure, favoring the adsorption of organic compounds. The Brunauer-Emmett-Teller surface area and total pore volume of KC-1 were 3442.2 and 1.68 cm 3 /g, respectively, which can be compared with those of KOH-activated carbons prepared from other precursors. Batch experiments were carried out to investigate the adsorption of naphthalene onto KC-1. The equilibrium data were analyzed by the Langmuir, Freundlich, and Polanyi- Manes isotherms and agreed with the Polanyi-Manes Model. The adsorption of naphthalene depended greatly on the porosity of the carbon, and the dispersive interactions between naphthalene and carbon could be relatively weak. The pH variation in aqueous solution had little effect on the adsorption process. The equilibrium time for 0.04 g/L of carbon dose was around 5 hr. Different models were used to evaluate the kinetic data and the pseudo second-order model was suitable to describe the kinetic process of naphthalene adsorption onto KC-1. Regeneration of spent carbon could be carried out effectively by alcohol treatment. The results indicated that KC-1 was a promising adsorbent for the removal of polycyclic aromatic hydrocarbons from aqueous solutions.     

Simultaneous removal of Congo red and cadmium(II) from aqueous solutions using graphene oxide–silica composite as a multifunctional adsorbent

Graphene oxide is a very high capacity adsorbent due to its functional groups and π?π interactions with other compounds. Adsorption capacity of graphene oxide, however, can be further enhanced by having synergistic effects through the use of mixed-matrix composite. In this study, silica-decorated graphene oxide (SGO) was used as a high-efficiency adsorbent to remove Congo red (CR) and Cadmium (II) from aqueous solutions. The effects of solution initial concentration (20 to 120 mg/l), solution pH (pH 2 to 7), adsorption duration (0 to 140 min) and temperature (298 to 323 K) were measured in order to optimize the adsorption conditions using the SGO adsorbent. Morphological analysis indicated that the silica nanoparticles could be dispersed uniformly on the graphene oxide surfaces. The maximum capacities of adsorbent for effective removal of Cd (II) and CR were 43.45 and 333.33 mg/g based on Freundlich and Langmuir isotherms, respectively. Langmuir and Freundlich isotherms displayed the highest values of Q_max for CR and Cd (II) adsorption in this study, which indicated monolayer adsorption of CR and multilayer adsorption of Cd (II) onto the SGO, respectively. Thermodynamic study showed that the enthalpy (ΔH) and Gibbs free energy(ΔG) values of the adsorption process for both pollutants were negative, suggesting that the process was spontaneous and exothermic in nature. This study showed active sites of SGO (π-π, hydroxyl, carboxyl, ketone, silane-based functional groups) contributed to an enormous enhancement in simultaneous removal of CR and Cd (II) from an aqueous solution, Therefore, SGO can be considered as a promising adsorbent for future water pollution control and removal of hazardous materials from aqueous solutions.     

La-EDTA coated Fe3O4 nanomaterial: Preparation and application in removal of phosphate from water

La-EDTA-Fe3O4 was prepared by a chemical co-precipitation method. The magnetic composite was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Furthermore, the adsorption properties of La-EDTA-Fe3O4 toward phosphate in water were investigated. The uptake rate of phosphate in water by La-EDTA-Fe3O4 was 3-1000 times than that of EDTA-Fe3O4 , and reached 97.8% at 7 hr. The adsorption process agreed well with the Freundlich model and kinetics studies showed that the adsorption of phosphate proceeds according to pseudo second-order adsorption kinetics. The maximum removal rate was achieved at pH 6.0-7.0. The La-EDTA-Fe3O4 had good adsorption properties and could be separated well from aqueous solution by a permanent magnet. Therefore, this nanomaterial has potential application for the removal of phosphate from large water bodies.     

Preparation1 and utilization of wheat straw anionic sorbent for the removal of nitrate from aqueous solution

In order to reduce the impact of eutrophication caused by agricultural residues (i.e. excess nitrate) in aqueous solution, economic and effective anionic sorbents are required. In this article, we prepared anionic sorbent using wheat straw. Its structural characteristics and adsorption properties for nitrate removal from aqueous solution were investigated. The results indicate that the yield of the prepared anionic sorbent, the total exchange capacity, and the maximum adsorption capacity were 350%, 2.57 mEq/g, and 2.08 mmol/g, respectively. The Freundlich isotherm mode is more suitable than the Langmuir mode and the adsorption process accords with the first order reaction kinetic rate equation. When multiple anions (SO42-, H2PO4-, NO3-, and NO2-) were present, the isotherm mode of prepared anionic sorbent for nitrate was consistent with Freundlich mode; however, the capacity of nitrate adsorption was reduced by 50%. In alkaline solutions, about 90% of adsorbed nitrate ions could be desorbed from prepared anionic sorbent. The results of this study confirmed that the wheat straw anionic sorbent can be used as an excellent nitrate sorbent that removes nitrate from aqueous solutions.     

生物炭对水中五氯酚的吸附性能研究

利用小麦秸秆和花生壳在300,400,600℃条件下制备生物炭,运用元素分析仪、扫描电镜和比表面积仪对生物炭的理化性质进行表征,同时探讨其对水中五氯酚(PCP)的吸附特性.结果表明,随炭化温度升高,生物炭芳香性增加,极性降低.花生壳生物炭对水中PCP的吸附效果优于小麦秸秆生物炭,3种温度制备的生物炭对PCP吸附量表现为400℃>600℃>300℃.随着生物炭添加量增大,水中PCP去除能力由81.79%提高至89.02%,生物炭的吸附量由30.32减小至5.54mg/g.生物炭对PCP的吸附动力学更符合准二级动力学方程,吸附等温线符合Freundlich方程.吸附过程主要受快速反应控制,降低反应温度有利于生物炭对水中PCP的吸附.     

小麦秸秆生物碳质吸附剂从水中吸附硝基苯的机理

在炭化温度为300℃下,以小麦秸秆为材料制备生物碳质吸附剂,采用批量平衡试验,研究了其对水中硝基苯的吸附特性,并从动力学及热力学角度探讨其吸附硝基苯的作用机理.结果表明,硝基苯在生物碳质上的吸附过程符合拉格朗日假二级动力学方程,反应活化能为12.2 kJ/mol;吸附行为可用Freundlich吸附等温方程描述,饱和吸附容量为91.58 mg/g.由吸附热力学方程计算得到的等量吸附焓变(ΔH)<0,吸附自由能变(ΔG)<0,吸附熵变(ΔS)>0,表明生物碳质对硝基苯的吸附为放热和熵减少的自发过程.     

磁性PEI功能化秸秆的制备及对Pb (Ⅱ)的吸附

为获得同时具有优良的吸附性能和磁分离特性的生物吸附材料,以汽爆秸秆为基质,采用戊二醛交联剂法制备了磁性聚乙烯亚胺功能化秸秆吸附剂（Fe₃O₄-PEI-RS）,通过SEM、XRD、FTIR、XPS和VSM等手段表征了材料的结构和性质,测定了Pb（Ⅱ）在Fe₃O₄-PEI-RS上的吸附性能,考察了pH、吸附时间、吸附剂投加量、Pb（Ⅱ）初始浓度、温度等因素对吸附的影响.结果表明,Fe₃O₄-PEI-RS对Pb（Ⅱ）的吸附具有强烈的pH依赖性;吸附时间对Pb（Ⅱ）的吸附效率有明显的影响,在180 min时吸附达到平衡,吸附过程符合准二级动力学模型;Langmuir和Freundlich模型都能很好地描述Pb（Ⅱ）在Fe₃O₄-PEI-RS上的吸附行为,20、30和40℃时最大吸附量分别为192.31、200.00和212.77 mg/g;热力学参数△G < 0,而焓变△H>0、△S>0,说明该吸附属于熵增加的自发吸热反应过程,升温有利于吸附.重复试验表明,EDTA作解吸剂,经5次吸附/解吸附循环后吸附剂仍能保持较高的吸附容量.研究显示,所制Fe₃O₄-PEI-RS对Pb（Ⅱ）具有较高的吸附容量,稳定性好、可循环利用,能在磁场下实现快速分离.      

磁性生物炭对水体中对硝基苯酚的吸附特性

为了制备同时具备磁分离和优良吸附性能的环境友好吸附材料,以棉花秸秆为生物质原料制备生物炭（CSBC）,采用共沉淀法制得磁性棉花秸秆生物炭（MCSBC）.通过元素分析、SEM、XRD、XPS、FTIR和VSM等对MCSBC进行表征,研究了CSBC和MCSBC对水中对硝基苯酚（PNP）的吸附特性.结果表明,溶液pH值对CSBC和MCSBC吸附PNP的影响较大,在酸性条件下的吸附量更大.CSBC和MCSBC对PNP的吸附动力学过程可被准二级动力学模型很好地描述,吸附过程包括液膜扩散和颗粒内扩散两个阶段.Langmuir、Freundlich和Sips模型都可以很好地描述PNP在CSBC和MCSBC上的吸附行为,最大吸附量分别为44.54和48.94mg/g,MCSBC相较于CSBC对PNP的吸附具有更好的效果.热力学研究结果表明,CSBC和MCSBC对PNP的吸附过程为熵增加的自发吸热过程.再生试验结果表明,经6次吸附-解吸循环后,MCSBC对PNP的吸附容量仍能达到初始吸附量的82%.     

氯化十六烷基吡啶改性活性炭对水中硝酸盐的吸附作用

采用阳离子表面活性剂氯化十六烷基吡啶(CPC)对活性炭进行了改性,并通过实验考察了CPC改性活性炭对水中硝酸盐的吸附作用.结果表明,CPC改性活性炭对水中的硝酸盐具备较好的吸附能力.CPC改性活性炭对水中硝酸盐的吸附能力明显高于未改性的活性炭.CPC改性活性炭对水中硝酸盐的吸附能力随着CPC负载量的增加而增加.CPC改性活性炭对水中硝酸盐的吸附动力学满足准二级动力学模型.CPC改性活性炭对水中硝酸盐的吸附平衡数据可以较好地采用Langmuir等温吸附模型加以描述.根据Langmuir等温吸附方程,CPC负载量(以活性炭计)为444 mmol·kg-1的改性活性炭对水中硝酸盐的最大单位吸附量为16.1 mg·g-1.CPC改性活性炭对水中硝酸盐的吸附能力随着pH的增加而降低.水中共存的氯离子、硫酸根离子和碳酸氢根离子会抑制CPC改性活性炭对水中硝酸盐的吸附.升高反应温度略微降低了CPC改性活性炭对水中硝酸盐的吸附能力.采用1 mol·L-1的NaCl溶液可以使95%左右吸附到CPC改性活性炭上的硝酸盐解吸下来.CPC改性活性炭吸附水中硝酸盐的主要机制是阴离子交换和静电吸引作用.上述实验结果说明,CPC改性活性炭适合作为一种吸附剂用于去除水中的硝酸盐.     

锆-十六烷基三甲基氯化铵改性活性炭对水中硝酸盐和磷酸盐的吸附特性

采用锆(Zr)和阳离子表面活性剂十六烷基三甲基氯化铵(CTAC)对活性炭进行联合改性,考察了所制备的Zr-CTAC改性活性炭对水中硝酸盐和磷酸盐的吸附去除作用,并探讨了相关的吸附去除机制.结果表明,Zr-CTAC改性活性炭对水中硝酸盐和磷酸盐均具备较好的吸附去除能力.Zr-CTAC改性活性炭对硝酸盐和磷酸盐吸附动力学过程满足准二级动力学模型.Langmuir、Freundlich和Dubinin-Radushkevich(D-R)等温吸附模型可以较好地描述Zr-CTAC改性活性炭对水中硝酸盐的等温吸附过程,Langmuir和D-R等温吸附模型可以较好地描述Zr-CTAC改性活性炭对水中磷酸盐等温吸附过程,通过Langmuir模型计算得到吸附剂对硝酸盐和磷酸盐的最大单位吸附量分别为7.58 mg·g-1和10.9 mg·g-1.高的p H会抑制Zr-CTAC改性活性炭对水中硝酸盐和磷酸盐的吸附.水中共存的Cl-、HCO-3和SO2-4等阴离子均会抑制Zr-CTAC改性活性炭对硝酸盐和磷酸盐的吸附,且对吸附硝酸盐的抑制作用较强而对吸附磷酸盐的抑制作用较弱.水中共存的磷酸盐对Zr-CTAC改性活性炭吸附硝酸盐的抑制作用较强,而水中共存的硝酸盐对Zr-CTAC改性活性炭吸附磷酸盐的抑制作用较弱.1 mol·L-1Na Cl溶液可以使90%左右被吸附到Zr-CTAC改性活性炭表面上的硝酸盐解吸下来.1 mol·L-1的Na OH溶液可以使78%左右被吸附到Zr-CTAC改性活性炭表面上的磷酸盐解吸下来.Zr-CTAC改性活性炭对硝酸盐的吸附机制主要包括阴离子交换作用和静电吸引作用,对磷酸盐的吸附机制主要包括配位体交换作用、阴离子交换作用和静电吸引作用.上述结果说明Zr-CTAC改性活性炭适合作为一种吸附剂去除废水中的硝酸盐和磷酸盐.     

碱改性小麦秸秆生物炭对水中四环素的吸附性能

以小麦秸秆为原料,在873K温度下炭化6h制备了小麦秸秆生物炭（WBC）,再用KOH浸渍法制备了3种碱炭比（质量比为1：1,2：1和3：1）的改性秸秆生物炭（WBCK1、WBCK2和WBCK3）.通过扫描电镜、比表面及孔径分析仪和傅里叶红外光谱对3种WBCK结构特征和表面性质进行表征.通过批量吸附实验,探讨了3种WBCK对溶液中四环素的吸附动力学和热力学特征.相比于WBC,WBCK有更丰富的孔径结构和更大的比表面积,且对四环素的吸附容量显著增加.3种WBCK对四环素的吸附动力学过程均符合准二级动力学模型,吸附速率常数大小顺序为k_2（WBCK2） > k_2（WBCK3）> k_{2（WBCK1）.}WBCK对四环素的吸附量随温度升高而增大,吸附过程同时存在物理吸附和化学吸附作用.Langmuir、Freundlich和Temkin模型均能较好地拟合吸附等温线,吸附机理较复杂.3种WBCK对四环素的吸附均为自发、吸热、熵增加过程.当溶液pH值范围为4.0~8.0时,3种WBCK对四环素的吸附性能较高.3种改性WBCK均可重复使用,其中WBCK2重复使用5次后吸附去除效率仅下降13.9%.     

木棉纤维对水中柴油的吸附性能

用木棉纤维作为吸附材料对含油废水进行吸附研究,考察了吸附平衡时间、等温吸附、以及溶液pH、溶液盐浓度等因素对油吸附的影响。溶液pH对吸附影响很小,在不同的盐浓度下吸附略有下降,木棉纤维吸附剂对0#柴油的吸附所需平衡时间为4h,在室温和pH=7左右的条件下,吸附材料对0#柴油的最大吸附量(qm)为(31±0.81)g/g,等温吸附线符合Langmuir和Freundlich模式,研究结果表明:木棉纤维对含油废水的吸附能在较短的时间达到吸附饱和,吸附量较大,对溶液环境的适应能力强,具有很好的应用前景。     

阴离子交换树脂对水杨酸的吸附与解吸性能

研究了714阴离子交换树脂对水中水杨酸的吸附与解吸性能,探讨了吸附的热力学和动力学特性.结果表明,树脂在pH=4～12时,吸附能力最好.等温吸附遵循Freundlich和Langmuir吸附平衡模型,为优惠吸附过程.在298～318K条件下,水杨酸吸附量为100～120mg/g的吸附焓变为-23.4-21.6kJ/mo...