铁基膨润土对水中磷酸根的吸附热力学及动力学研究

采用铁盐改性制得铁基膨润土,研究了其对水中磷酸根的吸附性能及影响因素,结果表明,通过对膨润土的改性提高了磷的去除率,含磷废水初始pH值的大小对磷的去除率影响不大,初始浓度越低越有利于磷的去除。磷的去除率随改性膨润土的投加量增大而提高,随温度升高而增大。进一步研究表明,改性膨润土对磷的吸附是吸热反应,其吸附等温线可采用Langmuir等温吸附方程拟合;改性膨润土对磷的吸附是快速吸附,在20 min内,磷去除率达70%以上,符合准二级吸附动力学模型。     

粉煤灰砖块对磷酸盐的吸附特性

以建筑废料粉煤灰砖块为吸附剂材料,通过静态吸附实验研究其对磷酸盐的吸附特征,以及磷酸盐初始浓度、吸附剂投加量、pH等因素对吸附反应的影响。Langmuir、Freundlich和Temkin等温模型的分析发现,Langmuir等温式方程最适合描述吸附过程,对磷酸盐的理论饱和吸附容量为44.62 mg/g。利用伪一级动力学模型、伪二级动力学模型和颗粒内扩散模型考察了吸附过程特征,其中伪二级动力学模型为最适于描述粉煤灰砖块对磷酸盐的吸附过程的动力学模型。通过颗粒内扩散模型、Bangham方程及Boyd模型对吸附动力学机理进行的探讨表明,颗粒内扩散速率不是粉煤灰砖块吸附磷酸盐反应的惟一速率控制步,膜扩散速率和颗粒内扩散速率共同影响着吸附反应速率。磷酸盐浓度较低时主要是膜扩散限制吸附反应速率,而磷酸盐浓度较高时则颗粒内扩散成为速率控制步。研究证明,粉煤灰砖块粉末作为湿地基质具有对磷酸盐很强的吸附能力,在减少了固体废弃物的数量的同时又可以实现水污染控制的目的。     

磷在磁铁矿-针铁矿混合相上的吸附

首次采用使用后贴式取暖物（商业名：热力贴）为原料制备吸附剂,元素分析、XRD、红外图谱综合鉴定为磁铁矿-针铁矿混合相（magnetite-goethite mix phase,MGM）,其比表面积为98.3 m2/g,平均粒径为510 nm,零电荷点在pH=5.7附近;磷在MGM上的吸附等温线符合Langmuir方程,其吸附历时曲线遵循准二级动力学模型,升温能促进磷的吸附;在实际废水磷浓度为51.8 mg/L、初始溶液pH=2的条件下,当MGM投加量为10 g/L时,磷的去除率为94.16%。     

Removal of aqueous nickel (II) using laterite as a low-cost adsorbent.

The present paper describes the laboratory study of laterite as a low-cost adsorbent for removal of aqueous nickel (II). At pH 7 and a temperature of 30 degrees C, a sorbent dose of 15 mg/L resulted in approximately 90% removal of nickel (II) from its initial concentration of 10 mg/L. A maximum removal of 98% of the adsorbate was observed with an adsorbent particle size of 210 micro with the above conditions. Batch kinetics results were described by fitting in a Langmuir isotherm. Helffrich's half-time equation (Helffrich, 1962) has been applied to evaluate the adsorption process. It appears that film diffusion would be the rate-limiting step. The effect of pH on the sorption process was carried out to a value of 8.0. The removal rate of nickel was found to be the function of pH of the reaction mixture. The rate of nickel uptake by laterite with the decrease in pH value has been explained on the basis of aqueous-complex formation and the subsequent acid-base dissociation at the solid-solution interface.     

Activated carbon from industrial solid waste as an adsorbent for the removal of Rhodamine-B from aqueous solution: kinetic and equilibrium studies

The activated carbon was prepared using industrial solid waste called sago waste and physico-chemical properties of carbon were carried out to explore adsorption process. The effectiveness of carbon prepared from sago waste in adsorbing Rhodamine-B from aqueous solution has been studied as a function of agitation time, adsorbent dosage, initial dye concentration, pH and desorption. Adsorption equilibrium studies were carried out in order to optimize the experimental conditions. The adsorption of Rhodamine-B onto carbon followed second order kinetic model. Adsorption data were modeled using both Langmuir and Freundlich classical adsorption isotherms. The adsorption capacity Q0 was 16.12 mg g(-1) at initial pH 5.7 for the particle size 125-250 microm. The equilibrium time was found to be 150 min for 10, 20 mg l(-1) and 210 min for 30, 40 mg l(-1) dye concentrations, respectively. A maximum removal of 91% was obtained at natural pH 5.7 for an adsorbent dose of 100mg/50 ml of 10 mg l(-1) dye concentration and 100% removal was obtained when the pH was increased to 7 for an adsorbent dose of 275 mg/50 ml of 20 mg l(-1) dye concentration. Desorption studies were carried out in water medium by varying the pH from 2 to 10. Desorption studies were performed with dilute HCl and show that ion exchange is predominant dye adsorption mechanism. This adsorbent was found to be both effective and economically viable.     

Kinetic, equilibrium isotherm and thermodynamic studies of Cr(VI) adsorption onto low-cost adsorbent developed from peanut shell activated with phosphoric acid

A particular agricultural waste, peanut shell, has been used as precursor for activated carbon production by chemical activation with H₃PO₄. Unoxidized activated carbon was prepared in nitrogen atmosphere which was then heated in air at a desired temperature to get oxidized activated carbon. The prepared carbons were characterized for surface area, surface morphology, and pore volume and utilized for the removal of Cr(VI) from aqueous solution. Batch mode experiments were conducted to study the effects of pH, contact time, particle size, adsorbent dose, initial concentration of adsorbate, and temperature on the adsorption of Cr(VI). Cr(VI) adsorption was significantly dependent on solution pH, and the optimum adsorption was observed at pH 2. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to analyze the kinetic data obtained at different initial Cr(VI) concentrations. The adsorption kinetic data were described very well by the pseudo-second-order model. Equilibrium isotherm data were analyzed by the Langmuir, Freundlich, and Temkin models. The results showed that the Langmuir adsorption isotherm model fitted the data better in the temperature range studied. The adsorption capacity which was found to increase with temperature showed the endothermic nature of Cr(VI) adsorption. The thermodynamic parameters, such as Gibb’s Free energy change (ΔG°), standard enthalpy change (ΔH°), and standard entropy change (ΔS°) were evaluated.     

溴化十六烷基吡啶改性沸石对水中甲基橙的吸附

采用溴化十六烷基吡啶(CPB)对天然沸石进行改性制备得到了CPB改性沸石,通过批量吸附实验考察了CPB改性沸石对水中阴离子染料甲基橙的去除作用。结果表明,天然沸石对水中甲基橙的吸附能力很差,而CPB改性沸石则可以有效吸附去除水中的甲基橙。CPB改性沸石对水中甲基橙的吸附能力随CPB负载量的增加而增加,CPB负载量最大的改性沸石对水中甲基橙的吸附能力最强。双分子层CPB改性沸石对水中甲基橙的去除率随吸附剂投加量的增加而增加,而CPB改性沸石对水中甲基橙的单位吸附量则随吸附剂投加量的增加而降低。双分子层CPB改性沸石对水中甲基橙的吸附平衡数据可以采用Langmuir等温吸附模型加以描述。根据Langmuir模型计算得到的CPB负载量为341 mmol/(kg沸石)的双分子层CPB改性沸石对水中甲基橙的最大吸附容量为63.7 mg/g(303 K和pH 7)。准二级动力学模型适合用于描述双分子层CPB改性沸石对水中甲基橙的吸附动力学过程。pH和反应温度对双分子层CPB改性沸石吸附水中甲基橙的影响较小。以上结果说明,双分子层CPB改性沸石适合作为一种吸附剂用于去除废水中的甲基橙。     

Removal of 2,4-D from aqueous solution by the adsorbents from spent bleaching earth

The removal of 2,4-D (2,4-dichlorophenoxyacetic acid) from aqueous solutions by activated spent bleaching earths (SBE) was studied at 20 degrees C. Experiments were performed as a function of time, initial concentration, dose and particle size of the adsorbent. The Langmuir and Freundlich adsorption equations were fitted by the adsorption data obtained. The values of Langmuir and Freundlich constants were determined. The adsorption kinetic was found to follow Lagergren equation. Both the boundary layer and intraparticle diffusion played important roles in the adsorption rate of 2,4-D. As the size of the adsorbent increased, the time to reach equilibrium increased but adsorption capacity decreased.     

Phenol removal from wastewater by adsorption on zeolitic composite

It is well known that adsorption is an efficient method of removal of various pollutants from wastewater. The present study examines the phenol removal from water by adsorption on a new material, based on zeolitic volcanic tuff. This compound contains zeolitic tuff and cellulose, another known adsorbent, in a mass ratio of 4 to 1. The performances of the new adsorbent composite were compared with those of a widely used adsorbent material, zeolitic volcanic tuff. The adsorbent properties were tested on batch synthetic solutions containing 1–10 mg L^?1 (1–10 ppm) phenol, at room temperature without pH adjustment. The influence of the adsorbent dose, pH and contact time on the removal degree of phenol from water was investigated. The experimental data were modeled using the Langmuir, Freundlich, and Temkin adsorption isotherms. The Langmuir model was found to best represent our data revealing a monolayer adsorption with a maximum adsorption capacity between 0.12 and 0.53 mg g^?1 at 25 °C, for 2.00 g of adsorbent, depending on the initial phenol concentration. The adsorption kinetic study was performed using a pseudo-first- and pseudo-second-order kinetic models illustrating that phenol adsorption on zeolite composite is well described by pseudo-first kinetic equations. Our results indicated that phenol adsorption on the new adsorbent composite is superior to that on the classic zeolite.     

Fluoride removal performance of a novel Fe-Al-Ce trimetal oxide adsorbent

A trimetal oxide was developed as a fluoride adsorbent by coprecipitation of Fe(II), Al(III) and Ce(IV) salt solutions with a molar ratio of 1:4:1 under alkaline condition. The material retained amorphous structure and maintained relatively stable fluoride adsorption performance at calcination temperatures lower than 600 degrees C. The optimum pH range for fluoride adsorption was 6.0-6.5 and the adsorbent also showed high defluoridation ability around pH 5.5-7.0, which is preferable for actual application. A high fluoride adsorption capacity of 178 mg g(-1) was acquired under an equilibrium fluoride concentration of 84.5 mg l(-1), adsorbent dose of 150 mg l(-1) and pH 7.0. The adsorption isotherm could be better described by the two-site Langmuir model than the one-site model, suggesting the existence of two types of active sites on the adsorbent surface. Coexistence of high concentrations of phosphate or arsenate only led to partial inhibition of fluoride adsorption, which further suggests the existence of heterogeneous adsorption sites. Sulfate and chloride did not affect fluoride adsorption, and nitrate influenced it only when the concentration of NO(3)(-)-N exceeded 50 mg l(-1). A high desorption efficiency of 97% was achieved by treating fluoride loaded Fe-Al-Ce oxide with NaOH solution at pH 12.2. A column experiment using the adsorbent fabricated into 1mm pellets was performed at an initial fluoride concentration of 5.5 mg l(-1), space velocity of 5h(-1) and pH of 5.8, and 2240 bed volumes were treated with the effluent fluoride under 1.0 mg l(-1).     

Removal of 2, 4‐D from aqueous solution by the adsorbents from spent bleaching earth

Abstract

The removal of 2, 4‐D (2, 4‐ dichlorophenoxyacetic acid) from aqueous solutions by activated spent bleaching earths (SBE) was studied at 20 °C. Experiments were performed as a function of time, initial concentration, dose and particle size of the adsorbent. The Langmuir and Freundlich adsorption equations were fitted by the adsorption data obtained. The values of Langmuir and Freundlich constants were determined. The adsorption kinetic was found to follow Lagergren equation. Both the boundary layer and intraparticle diffusion played important roles in the adsorption rate of 2, 4‐D. As the size of the adsorbent increased, the time to reach equilibrium increased but adsorption capacity decreased.     

改性松针对水体中铅(II)的吸附

探讨了改性松针(GXLsp)作为吸附剂对水体中铅离子的吸附性能,考察了吸附时间、溶液pH值、吸附剂用量、盐离子浓度、Pb(II)初始浓度及温度对改性松针吸附Pb(II)的影响。利用Langmuir和Freundlich等温线模型对实验数据进行非线性拟合分析,结果表明,Freundlich等温线模型能很好地描述松针对Pb(II)的吸附过程。热力学参数表明吸附是一个自发的吸热过程。改性松针对铅的吸附行为符合拟二级动力学方程,表明吸附过程是以化学吸附为主。在293K时松针对Pb(II)的饱和吸附量为318.3 mg/g,因此,GXLsp可作为一种高效低值生物质吸附剂以去除水体中重金属Pb(II)的污染。     

活化赤泥的除氟性能

以成本低的铝工业废矿渣（赤泥）为原材料,通过高温煅烧和酸化处理对赤泥进行活化,制备了除氟吸附剂。研究了反应时间、投加量、初始氟浓度、溶液温度、共存阴离子和pH值对活化赤泥除氟效果的影响。结果表明,接触反应时间为18 h时,吸附接近平衡。活化赤泥对氟离子的吸附符合Lagergren二级吸附动力学方程。另外,初始浓度越高,吸附容量越大。与Freundlich相比,Langmuir吸附等温模型可以更好地描述氟离子的吸附特性,最大吸附量可达2.71 mg/g。SO24-、Cl-和NO3-存在时（〈1 000 mg/L）,对氟离子的吸附几乎没有影响,然而,HCO3-、PO34-和氟离子共存时,会对氟吸附造成不利影响。活化赤泥在pH值3.5～11.0时,具有较好的吸附稳定性。活化赤泥是一种吸附容量高、性能稳定的环境友好型除氟材料,具有应用潜力。     

Prediction of adsorption rate of phosphate removal from wastewater with gas concrete

Gas concrete, a conventional structural material, is used to remove phosphate from wastewater. A batch study of phosphate removal from wastewater with waste particles of gas concrete has been performed. The concentration-time graphs were plotted against pH, temperature, and agitation speed, and the reaction rate equation was adapted to adsorption. The differential method was used to define reaction rate. The adsorption rates, reaction rate constants, and reaction rates were determined by tangent lines of drawn curves at different concentrations, depending on pH, temperature, and agitation speed. The adsorption rate increased with pH and temperature. The maximum effect of agitation speed on the adsorption rate was observed at 150 rpm. The activation energy of reaction and the pre-exponential factor were calculated using the Arrhenius equilibrium equation. The zeta potentials of waste gas concrete were determined at various pH values. The surface area of gas concrete was obtained using BET apparatus as 22 m2/g. The composition of gas concrete was determined by X-ray diffractometry. The results indicate that gas concrete is an effective adsorbent to remove phosphate from wastewater.     

炭化柚子皮对废水中双酚A的吸附

采用磷酸二氢钾活化原材料柚子皮,分别在300℃和600℃对活化后柚子皮进行炭化,制得吸附剂（CC300和CC600）,通过静态吸附实验研究了炭化柚子皮对双酚A的吸附性能。采用比表面积分析仪对炭化柚子皮进行表征,实验考察了pH值、吸附时间和温度对双酚A吸附的影响,并详细研究了炭化柚子皮对双酚A的吸附行为和机理。结果表明,高温炭化柚子皮（CC600）吸附双酚A能力比低温炭化（CC300）的强,其吸附较好地满足Langmuir和Freundlich等温方程;动力学研究表明,其吸附速率快,在150min内能达到吸附平衡,准二级动力学模型较好地描述该吸附行为,相关系数高达0．99：计算了热力学参数△G、△H和△S的值,△G为负值,说明该吸附过程为自发过程。     

Removal of MCPA from aqueous solutions by acid-activated spent bleaching earth

The removal of MCPA (4-chloro-2-methyl phenoxyacetic acid) from aqueous solutions by activated spent bleaching earth (SBE) was studied as a function of time, initial concentration, adsorbent concentration, and temperature. The Langmuir and Freundlich isotherms were fitted by the adsorption data obtained. The values of Langmuir and Freundlich constants were determined. The adsorption kinetics was described by the Lagergren equation. Mass transfer coefficient and thermodynamic parameters were also calculated. Column experiments were conducted and brekthrough capacities were found for different concentrations and different flow rates. The study demonstrates that acid-treated SBE could be used as an efficient adsorbent for the removal of MCPA-bearing wastewater effluents.     

Equilibrium and kinetics of adsorption of phosphate onto iron-doped activated carbon

Purpose

Two series of activated carbons modified by Fe (II) and Fe (III) (denoted as AC/N-Fe^II and AC/N-Fe^III), respectively, were used as adsorbents for the removal of phosphate in aqueous solutions.

Method

The synthesized adsorbent materials were investigated by different experimental analysis means. The adsorption of phosphate on activated carbons has been studied in kinetic and equilibrium conditions taking into account the adsorbate concentration, temperature, and solution pH as major influential factors.

Results

Maximum removals of phosphate are obtained in the pH range of 3.78?C6.84 for both adsorbents. Langmuir isotherm adsorption equation well describes the experimental adsorption isotherms. Kinetic studies revealed that the adsorption process followed a pseudo-second order kinetic model. Results suggest that the main phase formed in AC/N-Fe^II and AC/N-Fe^III is goethite and akaganeite, respectively; the presence of iron oxides significantly affected the surface area and the pore structure of the activated carbon.

Conclusions

Studies revealed that iron-doped activated carbons were effective in removing phosphate. AC/N-Fe^II has a higher phosphate removal capacity than AC/N-Fe^III, which could be attributed to its better intra-particle diffusion and higher binding energy. The activation energy for adsorption was calculated to be 22.23 and 10.89 kJ mol^?1 for AC/N-Fe^II and AC/N-Fe^III, respectively. The adsorption process was complex; both surface adsorption and intra-particle diffusion were simultaneously occurring during the process and contribute to the adsorption mechanism.     

Graphene—a promising material for removal of perchlorate (ClO4 −) from water

A batch adsorption process was applied to investigate the removal of perchlorate (ClO₄ ^?) from water by graphene. In doing so, the thermodynamic adsorption isotherm and kinetic studies were also carried out. Graphene was prepared by a facile liquid-phase exfoliation. Graphene was characterized by Raman spectroscopy, Fourier-transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscope, and zeta potential measurements. A systematic study of the adsorption process was performed by varying pH, ionic strength, and temperature. The adsorption efficiency of graphene was 99.2 %, suggesting that graphene is an excellent adsorbent for ClO₄ ^? removal from water. The rate constants for all these kinetic models were calculated, and the results indicate that second-order kinetics model was well suitable to model the kinetic adsorption of ClO₄ ^?. Equilibrium data were well described by the typical Langmuir adsorption isotherm. The experimental results showed that graphene is an excellent perchlorate adsorbent with an adsorbent capacity of up to 0.024 mg/g at initial perchlorate concentration of 2 mg/L and temperature of 298 K. Thermodynamic studies revealed that the adsorption reaction was a spontaneous and endothermic process. Graphene removed the perchlorate present in the water and reduced it to a permissible level making it drinkable.     

Arsenic(V) removal with a Ce(IV)-doped iron oxide adsorbent

The removal of arsenic(V) by a new Ce-Fe adsorbent was evaluated under various conditions. Under an initial As(V) of 1.0 mg l(-1), the adsorption capacity of the Ce-Fe absorbent was constant around a value of 16 mgg(-1) over a wide pH range (3-7), while a maximum adsorption capacity of 8.3 mgg(-1) was obtained over a narrow pH range around 5.5 for activated alumina, a conventional adsorbent. Kinetics of adsorption obeys a pseudo-first-order rate equation with the rate constant K(ad) as 1.84 x 10(-3) min(-1). The pattern of adsorption of As(V) by the adsorbent fitted well both the Langmuir and Freundlich models. A Langmuir Q(0) of 70.4 mgg(-1) was obtained at an initial pH of 5.0 and temperature of 20 degrees C, significantly higher than those of other adsorbents reported. Phosphate seriously inhibited the removal of As(V) while fluoride did not compete with As(V) even at an F/As molar ratio as high as 30, suggesting that the adsorption sites for As(V) and fluoride were different. Salinity, hardness, and other inorganic anions such as Cl(-), NO(3)(-), and SO(4)(2-) had no apparent effect on As(V) adsorption. Fourier transform infrared spectra of Ce-Fe adsorbent before and after As(V) adsorption demonstrated that M-OH groups plays an important role for As(V) ions removal in the adsorption mechanisms of Ce-Fe adsorbent.     

钢渣吸附处理苯酚废水的研究

采用恒温振荡的方法,考察了钢渣粒径、吸附温度、振荡速度、溶液pH值、溶液初始浓度对苯酚去除率的影响。结果表明,在粒径为120~180目、pH=4.0、苯酚溶液浓度在500 mg/L以内、苯酚/钢渣质量比为1∶1 000时吸附效果最好。钢渣对苯酚的吸附能较好地符合Langmuir和Freundlich吸附等温线,线性相关系数分别为0.9971和0.9916,吸附机理为表面吸附。