Sorptive removal of ibuprofen from water using selected soil minerals and activated carbon

Pharmaceuticals have gained significant attention in recent years due to the environmental risks posed by their versatile application and occurrence in the natural aquatic environment. The transportation and distribution of pharmaceuticals in the environmental media mainly depends on their sorption behavior in soils, sediment?Cwater systems and waste water treatment plants, which varies widely across pharmaceuticals. Sorption of ibuprofen, a non-steroidal anti-inflammatory drug, onto various soil minerals, viz., kaolinite, montmorillonite, goethite, and activated carbon, as a function of pH (3?C11), ionic strength (NaCl concentration: 0.001?C0.5?M), and the humic acid concentration (0?C1,000?mg/L) was investigated through batch experiments. Experimental results showed that the sorption of ibuprofen onto all sorbents was highest at pH 3, with highest sorption capacity for activated carbon (28.5?mg/g). Among the minerals, montmorillonite sorbed more ibuprofen than kaolinite and goethite, with sorption capacity increasing in the order goethite (2.2?mg/g)?<?kaolinite (3.1?mg/g)?<?montmorillonite (6.1?mg/g). The sorption capacity of the selected minerals increased with increase in ionic strength of the solution in acidic pH condition indicating that the effect of pH was predominant compared to that of ionic strength. An increase in humic acid concentration from low to high values made the sorption phenomena very complex in the soil minerals. Based on the experimental observations, montmorillonite, among the selected soil minerals, could serve as a good candidate to remove high concentrations of ibuprofen from aqueous solution.     

Cu(II) adsorption at the calcite-water interface in the presence of natural organic matter: Kinetic studies and molecular-scale characterization

We have characterized the adsorption of Suwannee River humic acid (SRHA) and Cu(II) on calcite from preequilibrated solutions at pH 8.25. Sorption isotherms of SRHA on calcite follow Langmuir-type behavior at SRHA concentrations less than 15 mg C L⁻¹, whereas non-Langmuirian uptake becomes evident at concentrations greater than 15 mg C L⁻¹. The adsorption of SRHA on calcite is rapid and mostly irreversible, with corresponding changes in electrostatic properties. At pH 8.25, Cu(II) uptake by calcite in the presence of dissolved SRHA decreases with increasing dissolved SRHA concentration, suggesting that formation of Cu-SRHA aqueous complexes is the primary factor controlling Cu(II) sorption at the calcite surface under the conditions of our experiments. We also observed that surface-bound SRHA has little influence on Cu(II) uptake by calcite, suggesting that Cu(II) coordinates to calcite surface sites rather than to surface-bound SRHA.Cu K-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS) spectroscopic results show that the local coordination of Cu adsorbed at the calcite surface is very similar in the presence and absence of SRHA. Ca backscatterers at ∼3.90 Å indicate that Cu(II) forms tetragonally distorted inner-sphere adsorption complexes in both binary and ternary systems. Subtle differences in the XANES and EXAFS between binary sorption samples and ternary sorption samples, however, prevent us from ruling out the formation of ternary Cu-SRHA surface complexes. Our findings demonstrate that SRHA plays an important role in controlling the fate and transport of Cu(II) in calcite-bearing systems.     

Selenite retention by nanocrystalline magnetite: Role of adsorption, reduction and dissolution/co-precipitation processes

We studied selenite () retention by magnetite () using both surface complexation modeling and X-ray absorption spectroscopy (XAS) to characterize the processes of adsorption, reduction, and dissolution/co-precipitation. The experimental sorption results for magnetite were compared to those of goethite (Fe^IIIOOH) under similar conditions. Selenite sorption was investigated under both oxic and anoxic conditions and as a function of pH, ionic strength, solid-to-liquid ratio and Se concentration. Sorption onto both oxides was independent of ionic strength and decreased as pH increased, as expected for anion sorption; however, the shape of the sorption edges was different. The goethite sorption data could be modeled assuming the formation of an inner-sphere complex with iron oxide surface sites (SOH). In contrast, the magnetite sorption data at low pH could be modeled only when the dissolution of magnetite, the formation of aqueous iron-selenite species, and the subsequent surface complexation of these species were implemented. The precipitation of ferric selenite was the predominant retention process at higher selenite concentrations (>1 × 10⁻⁴ M) and pH < 5, which was in agreement with the XAS results. Sorption behavior onto magnetite was similar under oxic and anoxic conditions. Under anoxic conditions, we did not observe the reduction of selenite. Possible reasons for the absence of reduction are discussed. In conclusion, we show that under acidic reaction conditions, selenite retention by magnetite is largely influenced by dissolution and co-precipitation processes.     

马兰煤矿矿井水水质变化特征及成因

通过对山西省马兰煤矿2号煤层采掘面在开采和封闭时期的矿井水和沉积物的研究,揭示采掘面封闭前后对矿井水水质和沉积物的影响机理。研究结果表明:马兰煤矿矿井水均为SO₄-Ca型水质,矿井水均富含SO₄2-和Fe离子;随着上部煤层的不断开采,3处矿井水呈现相同的变化规律,矿井水的pH值升高,Eh值降低,SO₄2-、Fe、Mn和Zn离子浓度随之下降,其中北一暗斜井处的矿井水水质变化最显著;矿井水水质指标和流速变化能够控制其沉积物的矿物组成和结晶程度,北一暗斜井处的沉积物在两次采样中由斯沃特曼铁矿变为针铁矿,而其他两处的矿井水沉积物矿物组分没有发生变化,主要由针铁矿组成。研究结果能够提高对老空区积水水质的预测精度,并对煤矿突水水源判识具有重要意义。      

Thermodynamics of U(VI) sorption onto Shewanella putrefaciens

We have conducted acid–base potentiometric titrations and U(VI) sorption experiments using the Gram negative, facultatively anaerobic bacterium Shewanella putrefaciens. Results of reversed titration studies on live, inactive bacteria indicate that their pH-buffering properties result from the equilibrium ionization of three discrete populations of functional groups. Carboxyl (pK_a=5.16±0.04), phosphoryl (pK_a=7.22±0.15) and amine (pK_a=10.04±0.67) groups most likely represent these three resolvable functionalities, based on their pK_a values. Site densities for carboxyl, phosphoryl and amine groups on the bacterial surface were approximately 31.7 μmol sites/g bacteria (0.35±0.02 sites/nm²), 8.95 μmol/g (0.11±0.007 sites/nm²) and 38.0 μmol/g (0.42±0.008 sites/nm²), respectively, based on an estimated bacterial specific surface area of 55 m²/g. Sorption experiments showed that U(VI) can reversibly complex with the bacterial surface in the pH 2–8 interval, with maximum adsorption occurring at a pH of 5. Sorption is not strongly sensitive to ionic strength (NaCl) in the range 0.02–0.10 M. The pH and ionic strength dependence of U(VI) sorption onto S. putrefaciens is similar to that measured for metal-oxide surfaces and Gram positive bacteria, and appears to be similarly governed by competitive speciation constraints. Measured U(VI) sorption is accounted for by using two separate adsorption reactions forming the surface complexes >COO–UO₂⁺ and >PO₄H–UO₂(OH)₂. Using S. putrefaciens as a model organism for dissimilatory metal-reducing Gram negative anaerobes, our results extend the applicability of geochemical speciation models to include bacteria that are capable of reductively solubilizing or precipitating a wide variety of environmentally and geologically important metals and metallic species.     

黄河小浪底水库水沙调控与流域硫循环

陆地风化的硫酸盐(SO42?)通过河流体系输入海洋,其通量以及硫酸盐同位素组成(δ34SSO4和 δ18OSO4)对全球硫循环及海洋SO42?同位素组成至关重要.河流体系SO42?含量及δ34SSO4和δ18OSO4组成不但受SO42?来源控制,而且受河流内部硫酸盐细菌还原及氧化过程影响,但其影响程度仍不明确,特别是拦...     

Sorption and transport of aqueous FeII in a goethite-coated sand column under anoxic conditions

Experiments were conducted under static batch and dynamic flow conditions to evaluate the sorption of Fe^II onto three goethites (G1, G2 and G3) having different crystal habits, morphologies and surface properties. Results reveal that G1 exhibited the highest Fe^II sorption extent and lowest kinetic rate constant, which may result from higher surface site density, surface roughness and edge surface faces. Surface complexation modeling parameters derived from batch experiments were combined with hydrodynamic parameters to simulate breakthrough curves in goethite-coated sand packed columns. The total sorbed amount of Fe^II at complete breakthrough was in agreement with that expected from the batch experiments, except for G1. Sorption breakthrough predictions that make use of surface complexation parameters accurately predicted Fe^II mobility in G2 and G3 columns, but poorly in G1 column. Experiments at various flow rates in G1 columns represented different amounts of Fe^II sorbed at complete breakthrough, thereby underscoring the impact of kinetic sorption. Moreover, Fe dissolution/re-precipitation or Fe^II-induced transformation of goethite was suspected at the lowest flow rate in the G1 column. The influence of goethite phase specific reactivity on Fe^II sorption under batch versus advective–dispersive flow is herein demonstrated. These findings have strong implications to assess transport of Fe^II and environmental contaminants both in natural and engineered systems.     

长江干流丰水期河水硫酸盐同位素组成特征及其来源解析

碳酸盐岩的硫酸风化机制及其与碳循环的关系是全球碳循环研究中最为关注的科学问题之一, 其关键问题是识别硫酸盐来源.通过分析长江干流丰水期SO₄2-浓度及其硫、氧同位素组成特征, 探讨长江硫酸盐的来源及其主要控制因素.长江河水SO₄2-含量呈现逐年增加的趋势, 并且年增幅度逐渐加大.δ34S_SO4和δ18O_SO4变化范围为-3.5‰~5.6‰和3.7‰~9.2‰, 二者呈现显著的线性负相关关系.δ18O_SO4值从上游到下游的增加趋势受长江水δ18O_H2O值的空间组成特征的影响.研究表明, 大气降水(酸雨)和硫化物氧化是控制长江干流丰水期河水硫、氧同位素组成及其来源的主要机制, 为研究长江流域化学风化侵蚀作用和碳循环过程提供重要的理论依据.      

Sorption and desorption of dissolved organic phosphorus onto iron (oxyhydr)oxides in seawater

Sorption of phosphorus (P) onto particulate surfaces significantly influences dissolved P concentrations in aquatic environments. We present results of a study contrasting the sorption behavior of several dissolved organic phosphorus (DOP) compounds and phosphate onto three commonly occurring iron (oxyhydr)oxides (Fe_ox): ferrihydrite, goethite, and hematite. The DOP compounds were chosen to represent a range of molecular weights and structures, and include: adenosine triphosphate (ATP), adenosine monophosphate (AMP), glucose-6-phosphate (G6P), and aminoethylphosphonic acid (AEP).All P compounds displayed decreasing sorption as a function of crystallinity of the Fe_ox substrate, with ferrihydrite adsorbing the most, hematite the least. In general, maximum sorption density decreased with increasing molecular weight of P compound; sorption of G6P onto goethite and hematite excepted. P compound size and structure, and the nature of the Fe_ox substrate all appear to play a role dictating relative sorption capacity. Failure of a simple, 1-step sorption-desorption model to describe the data suggests that P sorption cannot be explained by a simple balance between sorption and desorption. Instead, the data are consistent with a 2-step sorption model consisting of an initial rapid surface sorption, followed by a slow, solid-state diffusion of P from surface sites into particle interiors. Desorption experiments provide additional support for the 2-step sorption model.Without exception, DOP compounds showed less efficient sorption than did orthophosphate. This suggests that in aquatic systems enriched in reactive Fe_ox, whether as suspended particulates in the water column or in benthic sediments, DOP bioavailability may exceed that of orthophosphate. Since biological uptake of P from DOP requires enzymatic cleavage of orthophosphate, a system enriched in DOP relative to orthophosphate may impact ecosystem community structure.     

Blind prediction of Cu(II) sorption onto goethite: Current capabilities of diffuse double layer model

The paper presents examples illustrating the current blind predictive capabilities of the diffuse double layer model (DDLM) as the model requiring the smallest set of parameters and thus being most suitable for substituting even more empiric sorption approaches such as distribution coefficients K_D. The general strategy for the selection of numerical data are discussed. Based on the information about the minerals compiled in the sorption database RES³T (Rossendorf Expert System for Surface and Sorption Thermodynamics), first a set of relevant surface species is generated. Then relevant surface complexation parameters are taken from RES³T: the binding site density for the minerals, the surface protolysis constants, and the stability constants for all relevant surface complexes. To be able to compare and average thermodynamic constants originating from different sources, a normalization concept is applied.Our demonstration is based on a blind prediction exercise, i.e., the goal was not to provide optimal fits. The system considered is Cu(II) sorption onto goethite. The predictions are compared with raw data from three independent experimental investigations. The calculations were performed with the FITEQL 3.2 code. In most cases the model predictions represented the experimental sorption values for the sorbed amount of Cu(II), expressed as conventional distribution coefficients, within one order of magnitude or better.We conclude that the application of DDLM can indeed be used for estimating distribution coefficients for contaminants in well defined mineral systems. A stepwise strategy of species selection, data collection, normalization, and averaging is outlined. The SCM database so far assembled within the RES³T project is able to provide the parameter sets.     

硫化金属矿开采废石堆放对水环境的影响机理及对潜在治理措施的启示意义

金属硫化物矿山的废石堆场受降水淋滤影响而发生硫化物氧化,产生硫酸并释放重金属,因此采矿工程产生的废石是水污染不可忽视的来源。前人关于金属硫化矿物氧化的机理研究大多集中在单一矿物的室内实验,与野外情况匹配度较低。本研究从岩样(矿石和废石)、水样(河水、地下水、废弃尾矿库渗滤液)的水化学、微量元素和锶同位素等方面,分析某铅锌矿废石堆场对水环境的影响,并讨论其产生的化学组分在野外环境中的变化规律及机理。研究结果显示,金属硫化物氧化造成了河水酸化,pH低至2.38,SO₄2-高达9421 mg·L-1,同时微量元素中Zn、Pb、Ni、Mn、Cd质量浓度远超饮用水限值,如Zn达到了582 mg·L-1(饮用水限值为1 mg·L-1),且浓度与pH负相关。河水酸化的主因是黄铁矿、磁黄铁矿的氧化作用,并贡献了河水中大部分的SO₄2-。闪锌矿等矿物在贡献了河水中少部分SO₄2-的同时,也是重金属元素的主要来源。地下水离子浓度较河水低,pH在中性左右。虽然主要是受到侧向山体地下水补给稀释,但碳酸盐和硅酸盐对酸起到的中和作用对酸性水的治理有很大启示价值。以上机理的认识对于废石对水土环境污染的防治具有重要意义。     

Studies of Cd(II)-sulfate interactions at the goethite-water interface by ATR-FTIR spectroscopy

A combination of macroscopic experiments and in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy was used to study Cd(II)-sulfate interactions on the goethite-water interface. The presence of SO₄ dramatically promoted Cd adsorption at lower pH (pH 5.5-6.5) and had a smaller effect at higher pH. ATR-FTIR studies indicated sulfate adsorption on goethite occurred via both outer- and inner-sphere complexation. The relative importance of both complexes was a function of pH and sulfate concentration. ATR-FTIR spectra provided direct evidence of the formation of Cd-SO₄ ternary surface complexes on goethite. In addition to ternary complexes, Cd specifically sorbed on goethite promoted SO₄ adsorption via changing the surface charge, and caused additional SO₄ adsorption as both inner- and outer-sphere complexes. The relative importance of ternary complexes versus electrostatic effects depended upon pH values and Cd concentration. Ternary complex formation was promoted by low pH and high Cd levels, whereas electrostatic effects were more pronounced at high pH and low Cd levels. A portion of SO₄ initially sorbed in inner-sphere complexes in the absence of Cd was transformed into Cd-SO₄ ternary complexes with increased Cd concentration.     

招远金矿区水体中硫同位素特征及其对污染来源的指示

稳定同位素因其指纹效应已成为分析矿区污染来源的重要技术手段。文章以招远金矿区为例,应用硫同位素联合水化学分析、聚类分析及氢氧同位素分析招远金矿区水污染特征和成因。通过分析可知,矿区内地表水和地下水主要接受大气降水补给,水力联系密切。水化学类型以SO₄—Ca和SO₄—Na型为主,阴离子以SO₄2-为主,地表水和地下水的NO₃-和Cl-在空间上变异性较大。地表水硫酸盐含量普遍偏高,硫酸盐污染较为严重,高值区出现在玲珑金矿、金翅岭金矿和张星镇附近;而地下水高值区都出现在玲珑金矿附近,且SO₄2-浓度沿着径流方向逐渐降低。地表水中硫酸盐δ34S值介于1.8‰~9.8‰,地下水中硫酸盐δ34S值介于2.7‰~9.6‰,地表水和地下水硫酸盐含量受玲珑金矿硫化、玲珑花岗岩和胶东岩群影响明显。在地下水径流途中,有地表水入渗污染地下水的现象。另外,工业废水的排放也是硫酸盐含量升高的主要原因。研究表明:硫同位素在金矿区硫酸盐污染的来源和特征方面有很好的指示作用,是评价矿山开采对地下水污染的有效工具。     

山底河流域煤矿酸性矿井水野外监测

酸性矿井水在我国鲁西南、山西、内蒙、云南和贵州等煤矿区普遍存在,酸性矿井水其pH往往在2~5之间,高SO₄2?、HB、TDS、Fe、Mn。这些物质进入地下水、地表水或土壤后,会对其造成严重危害。文章选择山西阳泉市典型废弃煤矿区山底河流域为研究区,通过水文地质调查,水文地质钻探,水文地质剖面等方法阐述山底流域地层岩性,水文地质条件概况,得出受煤矿开采影响,与天然条件下相比山底河流域的地表水和地下水的补给、径流、排泄条件均发生了根本变化。补给通过破坏产生的导水裂隙带运移,以垂向运动为主;径流通过坑道,导水裂隙带运移,以横向运动为主;排泄以矿坑排水和泉水溢出方式为主。并简述山底河流域煤矿酸性矿井水试验站观测站分布情况与水化学特征。      

贵州乌江水系河水硫同位素组成特征研究

对乌江丰水期河水硫酸盐的硫同位素组成特征进行了研究。SO₄2-平均浓度为0.48 mmol/L,δ34S值为-11.5‰~8.3‰,干流河水δ34S值为-6.7‰~-3.9‰。河水的硫同位素组成主要受岩石风化及大气降水的影响,具有明显的区域性分异特征:上游碳酸盐岩地区河水的SO₄2-浓度高而δ34S值低,SO₄2-主要来源于煤中黄铁矿的氧化、矿床硫化物的氧化和大气降水;下游碳酸盐岩夹碎屑岩地区河水中的SO₄2-浓度低而δ34S值高,SO₄2-主要来源于大气降水和石膏溶解,煤中黄铁矿氧化生成的硫酸盐所占比重较低。乌江河水向贵州省外输出的SO₄2-通量为172×1010g/a,丰水期占全年SO₄2-输出总量的72%。来自煤、硫化物、雨水和蒸发岩的硫对丰水期河水中SO₄2-的平均贡献分别为:50%、25%、20%和5%。H₂SO₄对碳酸盐岩的侵蚀速率为35.1 t/km2/a(17.5 mm/ka),由此降低大气CO₂消耗速率3.66×105mol/km2/a。     

Surface complexation effects on phosphate adsorption to ferric iron oxyhydroxides along pH and salinity gradients in estuaries and coastal aquifers

Non-conservative behavior of dissolved inorganic phosphate (DIP) in estuaries is generally ascribed to desorption from iron and aluminum (hydr)oxides with increasing salinity. Here, we assess this hypothesis by simulating the reversible adsorption of phosphate onto a model oxide (goethite) along physico-chemical gradients representative of surface and subsurface estuaries. The simulations are carried out using a surface complexation model (SCM), which represents the main aqueous speciation and adsorption reactions of DIP, plus the ionic strength-dependent coulombic interactions in solution and at the mineral-solution interface. According to the model calculations, variations in pH and salinity alone are unlikely to explain the often reported production of DIP in surface estuaries. In particular, increased aqueous complexation of phosphate by Mg²⁺ and Ca²⁺ ions with increasing salinity is offset by the formation of ternary Mg-phosphate surface complexes and the drop in electrical potential at the mineral-water interface. However, when taking into account the downstream decrease in the abundance of sorption sites, the model correctly simulates the observed release of DIP in the Scheldt estuary. The sharp increase in pH accompanying the admixing of seawater to fresh groundwater should also cause desorption of phosphate from iron oxyhydroxides during seawater intrusion in coastal aquifers. As for surface estuaries, the model calculations indicate that significant DIP release additionally requires a reduction in the phosphate sorption site density. In anoxic aquifers, this can result from the supply of seawater sulfate and the subsequent reductive dissolution of iron oxyhydroxides coupled to microbial sulfate reduction.     

Goethite adsorption of Cu(II), Pb(II), Cd(II), and Zn(II) in the presence of sulfate: Properties of the ternary complex

Adsorption of Cu²⁺, Zn²⁺, Cd²⁺, and Pb²⁺ onto goethite is enhanced in the presence of sulfate. This effect, which has also been observed on ferrihydrite, is not predicted by the diffuse layer model (DLM) using adsorption constants derived from single sorbate systems. However, by including ternary surface complexes with the stoichiometry FeOHMSO₄, where FeOH is a surface adsorption site and M²⁺ is a cation, the effect of SO₄²⁻ on cation adsorption was accurately predicted for the range of cation, goethite and SO₄²⁻ concentrations studied. While the DLM does not provide direct molecular scale insights into adsorption reactions there are several properties of ternary complexes that are evident from examining trends in their formation constants. There is a linear relationship between ternary complex formation constants and cation adsorption constants, which is consistent with previous spectroscopic evidence indicating ternary complexes involve cation binding to the oxide surface. Comparing the data from this work to previous studies on ferrihydrite suggests that ternary complex formation on ferrihydrite involves complexes with the same or similar structure as those observed on goethite. In addition, it is evident that ternary complex formation constants are larger where there is a stronger metal-ligand interaction. This is also consistent with spectroscopic studies of goethite-M²⁺-SO₄²⁻ and phthalate systems showing surface species with metal-ligand bonding. Recommended values of ternary complex formation constants for use in SO₄-rich environments, such as acid mine drainage, are presented.     

Adsorption of Copper, Nickel, and Cadmium on Goethite in the Presence of Organic Ligands

Adsorption of copper, cadmium and nickel at low concentrations on goethite was studied in the presence of the simple organic ligands oxalate, salicylate, and pyromellitate. The experimental metal adsorption behavior was compared to calculations with a surface complexation model to evaluate the most important interactions. Oxalate mostly decreased Cu and Ni adsorption at high pH-values by competition between solution and surface complexation but had no effect on Cd adsorption. Cu adsorption in the presence of oxalate below pH 6 could best be described by defining a ternary complex of type A (surface-metal-ligand). Salicylate had only minor effects on metal adsorption. The adsorption of Cu in the presence of salicylate above pH 5 could be explained by a ternary complex of type A. Pyromellitate increased the adsorption of Cu and Cd in the acidic pH-range, likely by formation of ternary surface complexes of type B (surface-ligand-metal).     

Aridic crusts and vein mineralisations in the playa Areg el Makrzene, South Tunisia

The playa Areg el Makrzene is situated in the north of the escarpment of the Djebel Rehach in southern Tunisia. It is characterised by more than 70 spring mounds which are bound to faults in the Triassic sandstone, and by (sub-) recent calcareous and iron hydroxide precipitations. The artesian spring water contains high amounts of Na⁺, Ca²⁺, Mg²⁺ and Cl⁻, SO₄²⁻, and HCO₃, shows slightly alkaline character and a temperature of 25 °C. The spring mounds consist of porous travertine (calcite), goethite, gypsum and of Na–Mg evaporites and are up to 10 m high. Few metres away from the springs the amorphous iron hydroxides have altered to badly ordered goethite and ferrihydrite and finally to well ordered goethite. The muddy precipitate has altered to hard crusts (calcrete, ferricrete). The source of the precipitated material is discussed.

The faults in the sandstone are filled with (hydr-)oxides of iron and manganese, e.g. with goethite, hollandite and pyrolusite. The amount of Mn-oxides may reach 60 mass%.