共查询到20条相似文献，搜索用时 140 毫秒
1.
利用羟基氧化铁对硅藻土进行改性制备复合吸附剂,然后用一次平衡法研究了复合吸附剂对水体中铬酸根的吸附性能。实验结果表明:pH值为1.0,废水中Cr(VI)质量浓度不大于100 mg/L,吸附剂用量为0.5 g,吸附平衡时间为30min左右时,对六价铬的去除率达85%。动力学研究结果表明,Cr(Ⅵ)在复合吸附剂上的吸附动力学可以利用拟二级动力学方程较好的描述。吸附平衡研究结果表明,Cr(Ⅵ)在复合吸附剂上的吸附既可以利用Langmuir模型又可以利用Freundlich模型加以描述,这可能是由于复合吸附剂对Cr(Ⅵ)的吸附既有单层吸附又有多层吸附。 相似文献
2.
氧化锰、氧化铁、氧化铝对砷(Ⅲ)的吸附行为研究 总被引：6，自引：0，他引：6
合成了氧化锰、氧化铁、氧化铝三种矿物,以氧化铁、氧化锰为吸附剂研究了pH值、离子强度和时间等因素对吸附As(Ⅲ)的影响,并讨论了氧化锰、氧化铁、氧化铝三种矿物对As(Ⅲ)的饱和吸附容量及等温吸附实验。pH值对氧化锰吸附As(Ⅲ)几乎不影响,对氧化铁吸附As(Ⅲ)在很大的范围内(pH为3.5~8.5)影响不大,离子强度对二者吸附As(Ⅲ)的影响不大,吸附反应在0.5 h左右达到吸附平衡。在优化吸附条件下氧化锰、氧化铁、氧化铝对As(Ⅲ)的饱和吸附容量分别为48.38 mg/g、23.70 mg/g、3.52mg/g,三种合成矿物对As(Ⅲ)的饱和吸附容量:氧化锰氧化铁氧化铝。对实验数据进行Freundlich和Langmuir拟合,相关系数R均在0.98以上,吸附动力学符合Lagergren二级速率方程。 相似文献
3.
凹凸棒石铁/铝氢氧化物纳米复合材料对磷的吸附动力学研究 总被引：1，自引：0，他引：1
用铁/铝盐水解法制备了凹凸棒石/铝氢氧化物(PNCMⅠ)、凹凸棒石/铁氢氧化物(PNCMⅡ)和凹凸棒石/铁铝氢氧化物(PNCMⅢ)3种凹凸棒石纳米复合材料。对比了这3种纳米复合材料对水中磷的吸附净化能力,并利用吸附动力学实验探讨了3种材料对磷的吸附机理。结果发现:负载了铝/铁氢氧化物后凹凸棒石的晶体结构没有改变;温度对于3种吸附剂吸附磷的动力学参数影响不显著;3种吸附剂对磷的实际吸附量、理论吸附量和初始吸附速率均随着磷的初始浓度增大而增大。PNCMⅠ对磷的理论吸附量为18.18 mg/g,较其他2种吸附剂大。当磷的初始浓度从5 mg/L增加到50 mg/L,PNCM I对磷的初始吸附速率从0.125 mg/(g·min)增加到1.425 mg/(g·min)。3种凹凸棒石黏土纳米复合材料对磷的吸附符合准二级动力学方程,表明其吸附均为化学吸附。 相似文献
4.
为了研究不同煤级煤对H2S气体的吸附差异及吸附模型,采集新疆气煤,山西潞安瘦煤、晋城无烟煤3个煤样进行了工业分析、煤岩分析和平衡水条件下的等温吸附实验。采用Langmuir,BET,D-R和D-A吸附模型,利用拟合软件对等温吸附实验数据进行了非线性回归拟合,并检验拟合程度。结果表明:煤对H2S的吸附量随着煤化程度的加深而增加,为第Ⅰ类等温吸附线;其中Langmuir模型的拟合效果最好,n=1的D-A模型的拟合效果次之,BET模型的拟合效果较差,模型对实验数据的拟合效果与吸附模型中参数个数无明显关系;煤吸附H2S可用单分子层吸附理论来解释。 相似文献
5.
以氧化还原共沉淀的方法将铁锰复合氧化物负载于坡缕石黏土表面,制备负载型吸附剂,由静态吸附实验研究了吸附剂对磷的吸附性能,探讨了吸附的动力学特征、热力学参数和吸附机理。结果显示,吸附剂对磷的吸附受溶液初始pH值、吸附时间及温度的影响,在中性条件下吸附平衡时间为90 min,pseudo-second-order吸附动力学方程能较好描述吸附过程,吸附表观活化能为11.76 k J/mol;吸附等温线与Freundlich方程的拟合结果略优于Langmuir方程,由Langmuir方程得到最大吸附量为26~31 mg/g。吸附焓变为9.29 k J/mol,吸附熵变为正值,自由能变为-4.3~-5.8 k J/mol,吸附作用有多层不均匀吸附的性质,同时包含物理作用和化学作用,但不属强的化学键作用。 相似文献
6.
7.
以天然钙基膨润土和燃料废弃物粉煤灰为原料,工业淀粉为致孔剂,采用挤出-滚圆技术,制备了粉煤灰/膨润土复合颗粒吸附剂,并用于含Pb~(2+)溶液的吸附。研究了吸附时间、pH、投样量和溶液初始浓度对吸附性能的影响。结果表明,采用挤出-滚圆法制得的复合颗粒吸附剂大小均匀,表面没有裂纹,具有良好的机械强度。吸附实验中,在投样量10.0 g/L,溶液pH为6,吸附时间120 min,溶液初始浓度100 mg/L时,复合颗粒吸附剂对Pb~(2+)的去除率达到97.40%,吸附量为9.74mg/g。热力学实验表明吸附剂对Pb~(2+)的吸附更符合Langmuir吸附等温模型。 相似文献
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9.
模拟土样有机碳和矿物质对TCE吸附贡献的实验研究 总被引：2，自引：0，他引：2
为研究均一介质条件下有机碳含量及矿物质对TCE吸附行为的影响,简化了土壤环境的复杂性和异质性,以固定矿物质(高岭土∶石英砂=3∶7)作为土壤基体,添加不同质量分数的腐殖质(foc=0.16%~2.29%)配制成模拟土样,进行矿物质和模拟土样对TCE的吸附批实验。实验结果显示,TCE的吸附等温线呈非线性。随有机碳含量增加,表现为线性吸附增强,矿物质对TCE的吸附贡献随有机碳含量增加而减小。foc>0.82%时,矿物质对吸附作用的贡献率<5%;foc>1%时,可以基本忽略矿物质对吸附的影响。此外,TCE初始浓度也会影响有机碳和矿物质的吸附能力。用Freundlich模型分别拟合TCE吸附等温线的低浓度段和高浓度段(以Ce=500μg/L为浓度高低的分界),Freundlich指数n值呈现由大到小的趋势;TCE初始浓度越高,有机碳的吸附贡献率相对上升,而矿物质的贡献率则下降。TCE初始浓度在50~500μg/L之间、foc由0.16%增大到1%时,矿物质的吸附贡献率范围由28%~16%缩小到3%~1%之间,此时TCE初始浓度对有机碳和矿物质的吸附贡献率基本没有影响。 相似文献
10.
五氯苯酚在矿物表面吸附——实验、表面反应模式及其环境意义 总被引：4，自引：0，他引：4
利用批量平衡技术研究了石英、高岭石、伊利石、蒙脱石和铁氧化物对五氯苯酚(PCP)吸附的pH关系等温线和浓度关系等温线,发现所有矿物的pH关系等温线都表现出典型的峰形曲线特征,峰位在pH=5～6之间,依矿物不同而不同。基于矿物表面羟基位化合态和PCP的化合态考虑,提出一种包含表面络合反应和表面静电吸附反应的模式,对pH关系等温线计算拟合发现有很好的相关性。模式计算还表明,石英和层状硅酸盐矿物对PCP吸附以表面络合反应为主,而氧化铁矿物则包含表面络合反应和表面静电吸附反应,但以后者占主导,其反应平衡常数比前者大1～3个数量级。高岭石和氧化铁矿物的浓度吸附等温线可用Langmuir方程很好拟合,最大吸附量的大小顺序是赤铁矿>纤铁矿>针铁矿>高岭石>石英>蒙脱石≈伊利石,并可以用矿物表面羟基位浓度和反应机制加以解释。PCP在矿物表面可观的吸附量说明矿物表面吸附对憎水性可离解有机化合物(HIOCs)在天然水相体系和沉积中的迁移转化过程起着相当重要的作用。 相似文献
11.
S. Kahu A. Shekhawat D. Saravanan R. Jugade 《International Journal of Environmental Science and Technology》2016,13(9):2269-2282
Microwave-assisted tetrabutyl ammonium-impregnated sulphate-crosslinked chitosan was synthesized for enhanced adsorption of hexavalent chromium. The adsorbent obtained was extensively characterized using Fourier transform infrared, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray studies. Various isotherm models such as Langmuir, Freundlich and Dubinin–Radushkevich were studied to comprehend the adsorption mechanism of hexavalent chromium by the adsorbent. Maximum adsorption capacity of 225.9 mg g?1 was observed at pH 3.0 in accordance with Langmuir isotherm model. The sorption kinetics and thermodynamic studies revealed that adsorption of hexavalent chromium followed pseudo-second-order kinetics with exothermic and spontaneous behaviour. A column packed with 1 g of adsorbent was found to give complete adsorption of Cr(VI) up to 900 mL of 200 mg L?1 solution which discerns the applicability of the adsorbent material for higher sample volumes in column studies. The effective adsorption results were obtained due to both ion exchange and ion pair interaction of adsorbent with hexavalent chromium. Greener aspect of overall adsorption was regeneration of the adsorbent which was carried out using sodium hydroxide solution. In the present study, the regenerated adsorbent was effectively reused up to ten adsorption–desorption cycles with no loss in adsorption efficiency. 相似文献
12.
M. Fathizadeh Ph.D. H. Fakhraee A. Aroujalian 《International Journal of Environmental Science and Technology》2011,8(4):863-871
In this paper, the photocatalytic decontamination of hexavalent chromium and tri-ethyl phosphate, two important wastewater contaminants, are studied by the ultraviolet / nano-titanium dioxide process. The pH value and synergic effect between the oxidation of tri-ethyl phosphate and the reduction of hexavalent chromium were investigated in different concentrations of tri-ethyl phosphate and hexavalent chromium. Furthermore, the effects of ultraviolet and nano-titanium dioxide were investigated in a solution which contained tri-ethyl phosphate and hexavalent chromium. Results of adsorptions showed that hexavalent chromium was adsorbed better in acidic pH while the better adsorption for tri-ethyl phosphate was occurred in alkalinity pH. The reduction rate of hexavalent chromium was higher in acidic solutions while it was obtained at natural pH for tri-ethyl phosphate. In co-adsorption of hexavalent chromium and triethyl phosphate pollutants, tri-ethyl phosphate slightly increased adsorption of hexavalent chromium, but hexavalent chromium had no influence on the adsorption of tri-ethyl phosphate on nano-titanium dioxide particles. In contrast, triethyl phosphate has an improving effect on the reduction reaction rate of hexavalent chromium which increases with the interaction of the concentration of tri-ethyl phosphate in mixture. The same is true for the oxidation rate of tri-ethyl phosphate. 相似文献
13.
M. T. Ghaneian A. Bhatnagar M. H. Ehrampoush M. Amrollahi B. Jamshidi M. Dehvari M. Taghavi 《International Journal of Environmental Science and Technology》2017,14(2):331-340
Hexavalent chromium has been proved to be the reason of several health hazards. This study aimed at evaluating the application of pomegranate seeds powder for chromium adsorption (VI) from aqueous solution. Chromium adsorption percentage (VI) increased with increasing the adsorbent dosage. Chromium adsorption capacity (VI), at pH = 2 and 10 mg/L initial metal concentration, decreased from 3.313 to 1.6 mg/g through increasing dosage of adsorbent from 0.2 to 0.6 g/100 ml. The adsorption rate increased through increase in chromium initial concentration (VI). However, there was a removal percentage reduction of chromium (VI). Chromium adsorption kinetics by different models (pseudo-first-order, modified pseudo-first-order, pseudo-second-order, Elovich, intraparticle diffusion, Boyd kinetic) was investigated as well. Studies on adsorption kinetic indicated that the experimental data were matched by pseudo-second-order model (R 2 = 0.999) better. Obtained results demonstrated the pomegranate seeds can be used as an effective biomaterial and biosorbent for hexavalent chromium adsorption from aqueous solutions. 相似文献
14.
M. Aliabadi I. Khazaei H. Fakhraee M. T. H. Mousavian 《International Journal of Environmental Science and Technology》2012,9(2):319-326
The batch removal of hexavalent chromium from aqueous solutions using almond shell, activated sawdust, and activated carbon, which are low-cost biological wastes under different experimental conditions, was investigated in this study. The influences of initial concentration, adsorbent dose, adsorbent particle size, agitation speed, temperature, contact time, and pH of solution were investigated. The adsorption was solution pH dependent and the maximum adsorption was observed at a solution pH of 2.0. The capacity of chromium adsorption under equilibrium conditions increased with the decrease in particle sizes. The equilibrium was achieved for chromium ion after 30?min. Experimental results showed that low-cost biosorbents are effective for the removal of pollutants from aqueous solution. The pseudo-second-order kinetic model gave a better fit of the experimental data as compared to the pseudo-first-order kinetic model. Experimental data showed a good fit with the Freundlich isotherm model. Changes in the thermodynamic parameters, including Gibbs free energy (??Go), enthalpy (??Ho), and entropy (??So), indicated that the biosorption of hexavalent chromium onto almond shell, activated sawdust, and activated carbon was feasible, spontaneous, and endothermic in the temperature range 28?C50?°C. 相似文献
15.
M. Nameni M.Sc. M. R. Alavi Moghadam M. Arami 《International Journal of Environmental Science and Technology》2008,5(2):161-168
In this research, adsorption of chromium (VI) ions on wheat bran has been studied through using batch adsorption techniques. The main objectives of this study are to 1) investigate the chromium adsorption from aqueous solution by wheat bran, 2) study the influence of contact time, pH, adsorbent dose and initial chromium concentration on adsorption process performance and 3) determine appropriate adsorption isotherm and kinetics parameters of chromium (VI) adsorption on wheat bran. The results of this study showed that adsorption of chromium by wheat bran reached to equilibrium after 60 min and after that a little change of chromium removal efficiency was observed. Higher chromium adsorption was observed at lower pHs, and maximum chromium removal (87.8 %) obtained at pH of 2. The adsorption of chromium by wheat bran decreased at the higher initial chromium concentration and lower adsorbent doses. The obtained results showed that the adsorption of chromium (VI) by wheat bran follows Langmuir isotherm equation with a correlation coefficient equal to 0.997. In addition, the kinetics of the adsorption process follows the pseudo second-order kinetics model with a rate constant value of 0.131 g/mg.min The results indicate that wheat bran can be employed as a low cost alternative to commercial adsorbents in the removal of chromium (VI) from water and wastewater. 相似文献
16.
D. Sidiras D. Politi F. Batzias N. Boukos 《International Journal of Environmental Science and Technology》2013,10(6):1337-1348
In this work, a low-cost lignocellulosic adsorbent with high biosorption capacity is proposed, suitable for the efficient removal of hexavalent chromium from water and wastewater media. The adsorbent was produced by autohydrolyzing Scots Pine (Pinus Sylvestris) sawdust. The effect of the autohydrolysis conditions, i.e., pretreatment time and temperature, on hexavalent chromium biosorption was investigated using energy-dispersive X-ray spectroscopy (EDS) and UV–visible spectrophotometry. The Freundlich, Langmuir, Sips, Radke-Prausnitz, Modified Radke-Prausnitz, Tóth, UNILAN, Temkin and Dubinin-Radushkevich adsorption capacities and the rate constant values for pseudo-first- and pseudo-second-order kinetics indicated that the autohydrolyzed material exhibits significantly enhanced hexavalent chromium adsorption properties comparing with the untreated sawdust. The Freundlich’s adsorption capacity K F increased from 2.276 to 8.928 (mg g?1)(L mg?1)1/n , and the amount of hexavalent chromium adsorbed at saturation (Langmuir constant q m) increased from 87.4 to 345.9 mg g?1, indicating that autohydrolysis treatment at 240 °C for 50 min optimizes the adsorption behavior of the lignocellulosic material. 相似文献
17.
零价铁去除Cr(Ⅵ)的一系列批实验结果表明：水溶液中发生的氧化还原反应符合准一级反应；对于相同粒度的铁屑(比表面积2．89m^2／g)，固液比由05g／100mL增加到2．0g／100mL，Cr(Ⅵ)质量浓度达到排放标准所需反应时间从26．7min降为3．6min；在固液比相同、原水中Cr(Ⅵ)质量浓度不超过30mg／L时，原水质量浓度增大，达到饮用水标准的反应时间增加；其他条件相同，升高温度可提高零价铁与Cr(Ⅵ)的反应速率。 相似文献
18.
采用两种显微结构不同的螺旋状和管状构造的天然铁细菌矿化针铁矿和化学合成的α—FeOOH及两种有机高分子模板矿化结晶的β-FeOOH作为吸附材料，分别在pH=5和6时对含Cr^3 和Cr(Ⅵ)废水进行了吸附实验研究，结果表明，天然生物矿化针铁矿对金属阳离子和阴离子均有明显的吸附作用，其显微结构、大小和形态影响其吸附能力；纯化学合成的针铁矿对铬离子的吸附能力较低；通过有机模板合成的纳米微晶β-FeOOH对Cr^3 和Cr(Ⅵ)均有极高的去除率，这与其表面存在与有机分子络合作用、增大了其表面对金属离子和铬酸根的化学亲合力有关。 相似文献
19.
Sudipta Ghosh Somnath Mukherjee Ashraf Z. Al-Hamdan Krishna R. Reddy 《Geotechnical and Geological Engineering》2013,31(2):493-500
This paper evaluates the potential use of a fine-grained soil obtained from a site in West Bengal, India, as a suitable landfill liner material for the containment of hexavalent chromium from tanning waste sludge. The physico-chemical properties of the soil were determined. The soil adsorption affinity for hexavalent chromium was also assessed through adsorption batch and breakthrough column tests. The zero point charge (pHzpc) of the soil was found to be 7.3. The batch kinetics and column tests results indicated that the soil liner possesses a relatively good hexavalent chromium adsorption capacity at natural or slightly alkaline condition. The adsorption results showed that the hexavalent chromium uptake by the soil follows both Langmuir and Freundlich adsorption isotherms. This study also illustrated that the hexavalent chromium breakthrough curve in the column experiment reached equilibrium concentration after 3.5 pore volumes (900 h). Overall, this study showed that the fine-grained soil has the potential for usage as a landfill liner or as a component of a landfill barrier system to prevent chromium contamination from the tannery waste disposal. 相似文献