铁氧化物改性坡缕石粘土对Cr(Ⅵ)的吸附性能

以铁氧化物对坡缕石粘土进行包覆改性,通过静态吸附实验研究了改性坡缕石吸附Cr(Ⅵ)的特性,探讨了吸附的动力学特征、吸附平衡、热力学参数和吸附机理。结果显示,改性坡缕石对Cr(Ⅵ)的吸附随溶液初始pH值的升高显著减弱,在初始pH值为4.0时,吸附90 min可达平衡,吸附过程能较好地符合pseudo-second-order动力学方程,速率常数k₂随温度的升高增大,表观活化能为18.90 kJ/mol;吸附平衡能较好地符合Langmuir方程,吸附过程吸热,ΔH为28.29 kJ/mol,ΔG为-25～-20 kJ/mol,是物理吸附和化学吸附并存的过程。     

Cd2+在甘肃靖远坡缕石粘土上的吸附作用研究

以提纯后的甘肃靖远坡缕石粘土作吸附剂,常温下对水中Cd2 进行吸附实验,考察了吸附时间、吸附剂用量、振荡速率及pH值对吸附效果的影响,并对吸附动力学过程和吸附平衡进行了探讨.XRD和红外光谱分析结果显示,原矿在提纯后杂质石英被有效分离,得到了坡缕石含量较高的提纯样品.吸附实验结果显示,约60 min吸附反应可达平衡;pH值对吸附效果有显著影响,吸附率随pH值的升高而增加,当平衡溶液pH>8时吸附率超过99%;吸附过程与pseudo-second-order Lagergren动力学模型方程有较好的一致性,吸附平衡同时符合Langmuir和Freundlich等温吸附模型,由Langmuir方程得到饱和吸附量为31.65 mg/g.     

坡缕石粘土的磷吸附机制及其铁负载效果研究

比较了3种天然坡缕石粘土对不同程度磷污染水体的吸附净化能力,通过等温吸附实验和吸附动力学实验探讨了坡缕石粘土的磷吸附机制,并研究了不同形态铁负载对坡缕石粘土吸附净化磷污染水体性能和机制的影响.结果发现,3种天然坡缕石粘土对不同程度磷污染水体均有一定的吸附净化能力,其中含白云石较多的坡缕石粘土的磷吸附能力最强,吸附等温曲线呈S型,且Freundlich方程(R2=0.977 6)比Langmuir方程(R2=0.924 9)拟合效果更好;准一级方程、冥函数方程、抛物线扩散方程、准二级方程均能较好地模拟坡缕石粘土对磷的吸附动力学过程,说明坡缕石粘土对磷的吸附可能属于不均匀介质的多分子层吸附.此外,不同形态铁负载均能显著增强坡缕石粘土对不同程度磷污染水体的吸附净化能力,吸附等温曲线呈L型,Langmnir方程(Fe2 :R2=0.96,Fe3 :R2=0.967 7)比Freundlich方程(Fe2 :R2=0.965 7,Fe3 :R2=0.936 1)能略好地拟合铁负载坡缕石粘土的磷吸附等温结果,说明铁负载坡缕石粘土的磷吸附过程可能是均匀介质的单分子吸附.适量白云石有助于提高坡缕石粘土的磷吸附净化性能,铁负载可能通过改变坡缕石的表面电荷和吸附活性位点来改变其磷吸附机制,从而提高其磷吸附性能.     

坡缕石黏土负载铁锰复合氧化物吸附磷的性能

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。     

坡缕石粘土对Cu2+的吸附热力学

将坡缕石粘土分离提纯后作为吸附剂,通过对水中Cu2+的静态吸附实验,考察了时间及介质pH值对吸附效果的影响,并对吸附平衡和吸附热力学特征进行了探讨。结果表明:在实验条件下坡缕石粘土对水中的Cu2+离子具有较强的吸附作用,吸附平衡时间约为60 min,pH值对吸附效果有显著的影响,吸附量随pH值的升高而增加,当平衡溶液pH>7时吸附率超过99%;吸附平衡与Langmuir方程的符合程度优于D-R方程和Freundlich方程,由Langmuir方程拟合饱和吸附量为33.0～34.0 mg/g,由D-R方程得平均吸附能Es为13 kJ/mol,吸附过程为离子交换反应;吸附过程吸热,吸附焓为16.97 kJ/mol,吸附Gibbs函数在-27～-24 kJ/mol之间,吸附熵大于零,吸附过程可自发进行。     

有机坡缕石黏土对活性染料的吸附性能

由阴、阳离子表面活性剂对坡缕石黏土改性,通过静态吸附实验研究了有机坡缕石黏土对活性红的吸附性能,探讨了吸附平衡和吸附机理。结果表明,表面活性剂改性可增强坡缕石黏土表面的疏水性,影响ζ电位,适当配比的阴阳离子表面活性剂改性坡缕石黏土对活性红有协同吸附作用,吸附等温线呈非线性,符合Langmuir方程和Freundlich方程,ΔH为-12.23 k J/mol,吸附不存在强化学作用,是分配作用和氢键力、偶极间力及范德华力等多种作用的结果。     

聚合羟基铁铝蒙脱石复合体对磷的吸附行为及其动力学

在一定条件下利用钠基化蒙脱石合成了聚合羟基铝-蒙脱石复合体(HyA1-Mt)、2个不同铁含量的聚合羟基铁-蒙脱石复合体(HyFe-Mt)和3个不同Fe:Al摩尔比的聚合羟基铁铝-蒙脱石复合体(HyFeAl-Mt),研究了酸性和弱酸性条件下(pH=3.0～6.5)以上蒙脱石复合体对磷的吸附行为和动力学特征。结果表明,HyFeAl-Mt对磷的吸附容量大于HyA1-Mt和HyFe-Mt复合体,且随着Fe:Al摩尔比的增大,对磷的吸附容量依次增加。随pH升高,蒙脱石复合体对磷的吸附量容量变小。但随Fe:Al摩尔比增大,HyFeAl-Mt复合体零电荷点(pHZPC)升高,pH对磷的吸附的影响越来越小,HyFe-Mt对磷的吸附几乎不受pH的影响。随Fe:A1摩尔比的增大,HyFeAl-Mt对磷的吸附能力增强,铁含量是磷吸附量的重要控制因素。磷在各蒙脱石复合体上的吸附实验数据可很好地用Langmuir吸附等温方程拟合。磷在各蒙脱石复合体上的吸附动力学过程可分为快速和慢速两个过程,快速过程中的动力学受铁含量影响明显。动力学数据可同时用准二级动力学方程和Elovich方程拟合。     

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

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。     

坡缕石粘土对有机染料的吸附热力学研究

将甘肃靖远坡缕石粘土分离提纯,通过静态吸附实验,研究了坡缕石对水中有机染料亚甲基蓝、结晶紫和苯胺蓝的吸附等温线,探讨了吸附热力学特征.实验结果显示,在实验温度范围内3种染料在坡缕石上的吸附在30 min可达平衡,吸附等温线均能较好符合Langmuir模型,饱和吸附量大小顺序为:结晶紫＞亚甲基蓝＞苯胺蓝;吸附均为吸热过程,亚甲基蓝、结晶紫和苯胺蓝的吸附焓分别为15.52、9.26和2.59 kJ/mol;吸附Gibbs函数约为-35～-30 kJ/mol,吸附熵均大于零,吸附是自发过程.     

坡缕石对直接耐酸大红4BS的吸附动力学特征

研究了坡缕石对水中直接耐酸大红4BS的吸附动力学,在初始质量浓度为30~50 mg/L,转速为100~200 r/min,以及温度为303~348 K的范围内,坡缕石对直接耐酸大红4BS的吸附动力学数据均符合准二级速率方程。结果表明,坡缕石对直接耐酸大红4BS的吸附是外表面吸附,吸附表观活化能为11.92 kJ/mol,说明此吸附是由液膜扩散控制的物理吸附过程。     

磷酸根、铬酸根离子在低聚合羟基铁离子-蒙脱石复合体系中竞争吸附行为的实验研究

在模拟的氧化、酸性土壤条件下，用制备的低聚合羟基铁离子-蒙脱石复合体对磷酸根、铬酸根离子的竞争吸附进行实验研究发现：磷酸根离子和铬酸根离子的不同用量、不同添加顺序对竞争吸附的影响。并与蒙脱石和含水氧化铁对磷酸根离子、铬酸根离子的竞争吸附行为进行了对比。研究表明：在实验条件下，磷酸根离子、铬酸根离子在低聚合羟基铁离子蒙脱石复合体表面存在弱的竞争吸附现象。由于低聚合羟基铁离子蒙脱石复合体具有对磷酸根稍强的亲和性，在竞争吸附中，磷酸根离子处于稍有利的位置。     

苏州城市河道底泥对磷酸盐的吸附与释放特征

为了探讨苏州古城区河道底泥对磷酸盐的吸附-释放特征,文中分别从改变上覆水的pH值、底泥吸附-释放动力学和等温吸附实验三个方面进行了研究。结果表明:(1)随着上覆水pH值的增大,苏州河道底泥对磷的吸附量逐渐减小;(2)底泥对磷的吸附过程是一个复合动力学过程,通常包括快吸附和慢吸附两个过程。底泥对磷的快速吸附在2h内快速进行,之后为慢吸附过程,到6h左右,基本达到一种动态吸附平衡;底泥对磷释放的动力学过程也包括快释放和慢释放过程。底泥释放磷在1·5h内快速进行,之后进入慢释放过程,磷酸盐含量基本稳定,达到释放平衡;(3)底泥具有较大的吸附磷的能力。随着上覆水的磷酸盐浓度增高,底泥吸附磷酸盐的量也增加。上覆水与底泥的比值越大,底泥对磷的吸附率越小。     

几种铁（氢）氧化物对溶液中磷的吸附作用对比研究

铁(氢)氧化物不仅是土壤中广泛存在的矿物,也是重要的矿物资源。表生地质作用形成的针铁矿、赤铁矿和无定形氢氧化铁都具有纳米尺度,具有很高的表面积,表现出对磷的专性吸附,是低浓度磷的潜在吸附材料。本文通过铁(氢)氧化物对水溶液中磷酸根的等温吸附实验,初步对比研究了针铁矿、合成氧化铁黄、赤铁矿和无定形氢氧化铁对水中低浓度磷的吸附作用。结果表明,无定形氢氧化铁对水溶液中磷酸根的吸附能力最强(对低浓度磷的吸附达到5.5mg/g),其次是氧化铁黄和针铁矿,赤铁矿的吸附能力最差。几种铁(氢)氧化物对磷吸附容量的差别主要受比表面积控制。无定形氢氧化铁、合成氧化铁黄、针铁矿、赤铁矿对磷的吸附符合Freundlich等温方程。针铁矿和赤铁矿对磷的吸附动力学符合双常数速率方程。     

Adsorption of aluminium by a latosol as affected by phosphate and glutamic acid

The effect of phosphate and glutamic acid on adsorption of aluminium onto a latosol was investigated as a function of pH and ligand concentrations through batch equilibrium experiments. The results showed that adsorption of aluminium by the soil was enhanced after addition of phosphate at low pH, and this promotive effect was gradually eliminated with the increase in pH. The positive effect of phosphate on aluminium adsorption onto latosol was attributed to phosphate-induced surface negative charge and formation of ternary surface complexes involving aluminium and phosphate. While using silica as adsorbent, the inactive surfaces for phosphate, promotion of adsorption of aluminium by phosphate was also found. Then it was proposed that additional aluminium might bind to the phosphate adsorbed onto the silica in the form of surface complexes silica–aluminium–phosphate again, and the mechanism might operate in the soil systems as well. Glutamic acid exhibited no influence on the adsorption of aluminium by the soil at low pH. After increasing the pH, adsorption of aluminium was inhibited especially with the highest addition of glutamic acid, probably owing to weak affinity of complexes between glutamic acid and aluminium to the soil.     

Decontamination of hexavalent chromium and tri-ethyl phosphate stimulants through photacatalytic oxidation

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.     

Macroscopic and spectroscopic analysis of lanthanide adsorption to bacterial cells

This study was designed to combine surface complexation modelling of macroscopic adsorption data with X-ray Absorption Spectroscopic (XAS) measurements to identify lanthanide sorption sites on the bacterial surface. The adsorption of selected representatives for light (La and Nd), middle (Sm and Gd) and heavy (Er and Yb) lanthanides was measured as a function of pH, and biomass samples exposed to 4 mg/L lanthanide at pH 3.5 and 6 were analysed using XAS. Surface complexation modelling was consistent with the light lanthanides adsorbing to phosphate sites, whereas the adsorption of middle and heavy lanthanides could be modelled equally well by carboxyl and phosphate sites. The existence of such mixed mode coordination was confirmed by Extended X-ray Absorption Fine Structure (EXAFS) analysis, which was also consistent with adsorption to phosphate sites at low pH, with secondary involvement of carboxyl sites at high adsorption density (high pH). Thus, the two approaches yield broadly consistent information with regard to surface site identity and lanthanide coordination environment. Furthermore, spectroscopic analysis suggests that coordination to phosphate sites is monodentate at the metal/biomass ratios used. Based on the best-fitting pK_a site, we infer that the phosphate sites are located on N-acetylglucosamine phosphate, the most likely polymer on gram-negative cells with potential phosphate sites that deprotonate around neutral pH.     

Adsorption of phosphate on tidal flat surface sediments from the Yangtze Estuary

Adsorption of phosphate (PO₄-P) by sediments of nine sites taken from the Yangtze Estuarine and coastal tidal flats were studied in a laboratory. The results indicate that the process of phosphorus adsorption onto sediments mainly occurred within 0-10 h, and then reached a dynamic equilibrium. This experimental finding has shown maximum adsorption rates (ad-R) occurred within 0-0.5 h, ranging from 10.40-56.40 mg/kg h with regional differences. The adsorption rates were obviously related to concentrations of fine particles (<63 µm) in the sediments. Adsorption isotherm curves were fitted to the modified Langmuir equation. Adsorption capacities (ad-C) varied from 26.32 to 204.08 mg/kg, and showed good affinities for Fe³⁺ and TOC concentrations. The adsorption efficiency (ad-E) of phosphate on sediments ranged from 21.55 to 248.30 L/kg, showing a close correlation with TOC concentrations. A correlation between environmental factors and phosphate adsorption is presented in this experiment. Phosphate adsorption is susceptible to changes in pH, temperature and salinity conditions.     

Organic matter on clay minerals and marine sediments — effect on adsorption of dissolved copper,phosphate, and lipids from saline solutions

Adsorption of dissolved copper and phosphate by natural and peroxide-treated marine sediments was compared. A three-fold increase in copper adsorption and a six-fold increase in phosphate adsorption was caused by the peroxide treatment. Indigenous organic matter evidently interferes with adsorption.Clay minerals coated with heptadecanoic acid adsorbed somewhat less copper, phosphate, and hexadecane than uncoated clays, but slightly more nonadecanoic acid and anthracene.     

Evaluation of coal as adsorbent for phosphate removal

This paper reports the adsorption of phosphate ions on coal, charcoal, and coal ash. The influences of factors such as contact time, and initial adsorbate concentration have been studied. Adsorption of phosphate ions on virgin coal was significant compared to charcoal, coal and coal ash evacuated at 200°C. The significant adsorption capability of coal is due to the porosity as well as due to organic carbon and inorganic elements present in coal. The evacuation of coal proved to be ineffective in enhancing its capability for phosphate ions retention. The adsorption behaviors of all the three adsorbent used was conformed using Freundlich’s adsorption model. The results suggest that coal could be used as an efficient adsorbent for removing phosphate ions from wastewater.     

Adsorption of palmitic acid on calcite

The adsorption of palmitic acid by calcite was determined as a function of palmitic acid concentration and salinity. Adsorption isotherms were generally of the S-type, indicating probable hydrophobic interaction of adsorbed species. The effect of increased salinity was to increase adsorption from 0–25 ppt, then to decrease adsorption from 25–35 parts per thousand. The adsorption increase results from decreased solubility, whereas the adsorption decrease may be related to micelle formation. Dissolved Mg²⁺ was found to strongly inhibit fatty acid adsorption. Desorption of surface-bound phosphate was associated with palmitic acid adsorption. The relationship between adsorbed Mg²⁺, phosphate and palmitic acid suggests investigation of adsorption behavior of natural phospholipid compounds.