Removal of estrone and 17beta-estradiol from water by adsorption

Endocrine disrupting chemicals (EDCs) are the focus of current environment concern, as they can cause adverse health effects in an intact organism, or its progeny, subsequent to endocrine function. The paper reports on the removal of estrone (E1) and 17beta-estradiol (E2) from water through the use of various adsorbents including granular activated carbon (GAC), chitin, chitosan, ion exchange resin and a carbonaceous adsorbent prepared from industrial waste. The results show that the kinetics of adsorption were adsorbent and compound-dependent, with equilibration being reached within 2 h for a waste-derived carbonaceous adsorbent to 71 h for an ion-exchange resin for E1, and within 7 h for the waste-derived carbonaceous adsorbent to 125 h for GAC for E2. Of all the adsorbents tested, the carbonaceous adsorbent showed the highest adsorption capacity, with a maximum adsorption constant of 87500 ml/g for E1 and 116000 ml/g for E2. The GAC also had a very high adsorption capacity for the two compounds, with a maximum adsorption constant of 9290 ml/g for E1 and 12200 ml/g for E2. The effects of some fundamental environmental parameters including adsorbent concentration, pH, salinity and the presence of humic acid and surfactant on adsorption were studied. The results show that adsorption capacity of activated carbon was decreased with an increase in adsorbent concentration and by the presence of surfactant and humic acid. The results have demonstrated excellent performance of a waste derived adsorbent in removing E1 and E2 from water, and indicated the potential of converting certain solid waste into useful adsorbents for pollution-control purposes.     

Removal of naphthalene from aqueous solution on chemically modified activated carbons

The aim of this work was to correlate the textural and chemical features of carbonaceous adsorbents with the adsorption capacity of naphthalene from aqueous phase, at the concentration in which this compound is usually found in wastewater from coke ovens. The study reveals that the adsorption capacity in different carbon materials depends not only on the textural characteristics of the material but also on the functionalities of the activated carbons. The micropores of the adsorbents, particularly those of narrower diameter, were found to be active sites for the retention of naphthalene. In contrast, the modification of the surface chemistry of the carbon materials led to a decrease in the adsorption capacities. Dispersive forces play an important role, and adsorbents with a higher non-polar character have proven to be more efficient for the naphthalene adsorption. This behaviour has been linked to the presence of specific interactions between the basal planes and the polyaromatic structure of the naphthalene molecule.     

Removal of antibiotics from water using sewage sludge- and waste oil sludge-derived adsorbents

Sewage sludge- and waste oil sludge-derived materials were tested as adsorbents of pharmaceuticals from diluted water solutions. Simultaneous retention of eleven antibiotics plus two anticonvulsants was examined via batch adsorption experiments. Virgin and exhausted adsorbents were examined via thermal and FTIR analyses to elucidate adsorption mechanisms. Maximum adsorption capacities for the 6 materials tested ranged from 80 to 300 mg/g, comparable to the adsorption capacities of antibiotics on various activated carbons (200-400 mg/g) reported in the literature. The performance was linked to surface reactivity, polarity and porosity. A large volume of pores similar in size to the adsorbate molecules with hydrophobic carbon-based origin of pore walls was indicated as an important factor promoting the separation process. Moreover, the polar surface of an inorganic phase in the adsorbents attracted the functional groups of target molecules. The presence of reactive alkali metals promoted reaction with acidic groups, formation of salts and their precipitation in the pore system.     

活性炭吸附水中酚类内分泌干扰物试验研究

考察了两种不同表面化学性质粉末活性炭（WP及其改性炭WPN）对松花江原水和砂滤水中六种加标酚类内分泌干扰物的去除情况。试验结果表明,活性炭对六种目标物的吸附能力与其憎水性（logKOW）有关,依次为：4-n—NP〉E1〉DES〉EE2〉E2〉BPA;活性炭吸附降低了水中的TOC与UV254值,同时也去除了水中大部分的内分泌干扰物,WP和WPN两种活性炭对江水和砂滤水中六种目标物的去除率分别为26．82％～85．97％和74．62％～96．64％,其中WPN的吸附效果相对较好。试验结果还表明,活性炭对酚类内分泌干扰物的吸附能力受水中有机物与活性炭物化性质的影响较大,通过一定的改性处理获得孔结构与表面化学性质均有利于去除水中有机污染物的活性炭,并将其用于给水的深度处理,对于提高活性炭的吸附能力、使用寿命及确保出水水质安全都具有重要意义。     

Simultaneous uptake of anionic surfactants and micellar-solubilized contaminants using anion-exchange resins

This research studied simultaneous uptake of anionic surfactants and micellar-solubilized organic contaminants by anion-exchange resins. Anionic surfactant molecules adsorbed onto the positively charged resin mainly through electrostatic attraction, while the micellar-solubilized contaminants were excluded from aqueous solutions once the remaining micelles could no longer solubilize them. Data suggest that the excess contaminants adsorbed onto the resin skeleton and admicelle layer formed on the resin surface through hydrophobic interactions and eventually partitioned into the resin gel phase matrix. In batch adsorption, the contaminant solubilization capacity did not decrease linearly with respect to surfactant concentration decrease due to the increased solution counterion activity during anion exchange, and caused "delayed" contaminant uptake relative to that of the surfactant. No such effect occurred in continuous column adsorption, where the surfactant and contaminant breakthrough occurred simultaneously. Surfactant head and tail group properties, along with resin structure and particle size significantly affected surfactant and contaminant uptake rates. Relative to recovering the surfactant, the high exchange potential of the anionic surfactant prevented effective surfactant desorption, even at high electrolyte concentration and in the presence of a cosolvent. The resin matrix also had high affinity for the partitioned contaminant, and the contaminant elution from the resin seemed to be controlled by equilibrium partitioning.     

Removal of perfluorooctane sulfonate from wastewater by anion exchange resins: Effects of resin properties and solution chemistry

Perfluorooctane sulfonate (PFOS) is a new persistent organic pollutant of substantial environmental concern, and its removal from industrial wastewater is critical to eliminate its release into water environment. In this paper, six anion exchange resins with different polymer matrix, porosity, and functional group were evaluated for PFOS removal from simulated wastewater. Resin matrix displayed significant effect on the sorption kinetics and capacity of PFOS, and the polyacrylic resins including IRA67 and IRA958 exhibited faster sorption and higher sorption capacity for PFOS than the polystyrene resins due to the hydrophilic matrix. Sorption isotherms illustrated that the sorption capacity of PFOS on IRA67 and IRA958 was up to 4-5 mmol/g, and the amount of PFOS sorbed on the resins was more than chloride released from resins, indicating that other interactions besides anion exchange were involved in the sorption. Solution pH had little impact on the sorption of PFOS on IRA958, but displayed significant effect on IRA67 at pH above 10 due to the deprotonation of amine groups. The coexisting sulfate and hexavalent chromium in wastewater interfered with the sorption of PFOS because of their competitive sorption on the exchange sites. The spent resins were successfully regenerated using the mixture of NaCl and methanol solution. This work provided an understanding of sorption behavior and mechanism of PFOS on different anion exchange resins, and should result in more effective applications of ion exchange for PFOS removal from industrial wastewater.     

Evaluation of Victorian low rank coal-based adsorbents for the removal of organic compounds from aqueous systems

Three activated carbons and two chars made from low rank coal were evaluated in terms of their ability to remove the organic compound 4-nitrophenol (4-NP) and natural organic matter (NOM) from aqueous systems. The adsorption equilibrium capacities of all adsorbents for 4-NP correlated with the micropore area of the adsorbents. Adsorption rates showed improved removal with decreasing particle size and higher carbon mass loadings. A pseudo first order model was used to fit the kinetic data, with a correlation coefficient of 0.995–0.999 for all systems.

The adsorption capacity for NOM, as measured by UV-absorbing DOC, correlated well with the pore volume and pore surface areas for pores with diameters in the range 2.7–21 nm. The trend in the adsorption capacities and removal rates of the adsorbents for NOM provided evidence that the pore size distribution is one of the most important physical characteristics of activated carbon for the adsorption of NOM.

The performance of activated low rank coal based materials was comparable to a high quality coconut-based commercial carbon in batch systems. Although the non-activated char adsorbents gave poor performance, they have potential for use in applications where poor performance can be outweighed by lower cost.     

Effect of linear alkylbenzene sulphonates (LAS) on the anaerobic digestion of sewage sludge

Batch anaerobic biodegradation tests with different alkylbenzene sulphonates (LAS) at increasing concentrations were performed in order to investigate the effect of LAS homologues on the anaerobic digestion process of sewage sludge. Addition of LAS homologues to the anaerobic digesters increased the biogas production at surfactant concentrations 5-10 g/kg dry sludge and gave rise to a partial or total inhibition of the methanogenic activity at higher surfactant loads. Therefore, at the usual LAS concentration range in sewage sludge, no adverse effects on the anaerobic digesters functioning of a wastewater treatment plant (WWTP) can be expected. The increase of biogas production at low surfactant concentrations was attributed to an increase of the bioavailability and subsequent biodegradation of organic pollutants associated with the sludge, promoted by the surfactant adsorption at the solid/liquid interface. When the available surfactant fraction in the aqueous phase instead of the nominal surfactant concentration was used to evaluate the toxicity of LAS homologues, a highly significant relationship between toxicity and alkyl chain length was obtained. Taking into account the homologue distribution of commercial LAS in the liquid phase of the anaerobic digesters of a WWTP, an EC(50) value of 14 mg/L can be considered for LAS toxicity on the anaerobic microorganisms.     

水中重金属离子吸附材料的研究现状与发展趋势

系统介绍了无机吸附材料（碳质类、矿物类、金属氧化物类）、有机高分子吸附材料（纤维素、壳聚糖、农林废弃物、离子交换树脂等）和复合型吸附材料（有机/有机型、无机/无机型、有机/无机型）等重金属离子吸附材料的物化特性和结构特点,对上述材料去除水体典型重金属离子的吸附容量、吸附机理、工程应用进展等进行了综述。阐述了纳米材料、离子选择性材料和可降解生物质材料等新型重金属离子吸附材料的研究现状及发展趋势。结果表明:开发价格低廉、吸附容量高、选择性高、可再生且环境友好的吸附材料是重金属离子吸附研究的重要方向;结合现代化检测技术和分析手段,探索吸附过程中吸附剂与重金属离子间相互作用的本质,对于拓展吸附机理和开发性能优良的吸附材料具有重要的理论和实际意义。     

Removal of water pollutants with activated carbons prepared from H3PO4 activation of lignin from kraft black liquors

Activated carbons with a high BET surface area and a well-developed porosity have been prepared from pyrolysis of H3PO4-impregnated lignin precipitated from kraft black liquors. Impregnation ratios within the range of 1-3 and activation temperatures of 623-873 K have been used, giving rise to carbons with different porous and surface chemical structure. Increasing the activation temperature and the impregnation ratio leads to a widening of the porous structure with a higher relative contribution of mesoporosity. The potential application of these carbons for the removal of water pollutants has been investigated by measuring their adsorption capacities for phenol, 2,4,5-trichlorophenol and Cr (VI) as representative of toxic contaminants found in industrial wastewaters. The results obtained compare well and even favorably with those reported in the literature for other activated carbons. An impregnation ratio and an activation temperature around 2 g H3PO4/g lignin and 700 K, respectively, are recommended as the best combination of operating conditions to prepare activated carbons for aqueous phase applications although at lower values of these two variables carbons with good adsorption capacities are also obtained.     

Anchorage of iron hydro(oxide) nanoparticles onto activated carbon to remove As(V) from water

The adsorption of arsenic (V) by granular iron hydro(oxides) has been proven to be a reliable technique. However, due to the low mechanical properties of this material, it is difficult to apply it in full scale water treatment. Hence, the aim of this research is to develop a methodology to anchor iron hydro(oxide) nanoparticles onto activated carbon, in which the iron hydro(oxide) nanoparticles will give the activated carbon an elevated active surface area for arsenic adsorption and also help avoid the blockage of the activated carbon pores. Three activated carbons were modified by employing the thermal hydrolysis of iron as the anchorage procedure. The effects of hydrolysis temperature (60-120 °C), hydrolysis time (4-16 h), and FeCl₃ concentration (0.4-3 mol Fe/L) were studied by the surface response methodology. The iron content of the modified samples ranged from 0.73 to 5.27%, with the higher end of the range pertaining to the carbons with high oxygen content. The materials containing smaller iron hydro(oxide) particles exhibited an enhanced arsenic adsorption capacity. The best adsorbent material reported an arsenic adsorption capacity of 4.56 mg As/g at 1.5 ppm As at equilibrium and pH 7.     

Batch and column adsorption of herbicide fluroxypyr on different types of activated carbons from water with varied degrees of hardness and alkalinity

There has been little research into the effects of the water hardness and alkalinity of surface waters on the adsorption of herbicides on activated carbons. The aim of this study was to determine the influence of these water characteristics on fluroxypyr adsorption on different activated carbons. At low fluroxypyr surface concentrations, the amount adsorbed from distilled water was related to the surface hydrophobicity. Surface area of carbons covered by fluroxypyr molecules ranged from 60 to 65%. Variations in fluroxypyr solubility with water hardness and alkalinity showed a salting-in effect. Calcium, magnesium and bicarbonate ions were adsorbed to a varied extent on the activated carbons. The presence of fluroxypyr in solution decreased their adsorption due to a competition effect. K_F from the Freundlich equation linearly increased with water hardness due to salt-screened electrostatic repulsions between charged fluroxypyr molecules. The amount adsorbed from distilled water was largest at high fluroxypyr solution concentrations, because there was no competition between inorganic ions and fluroxypyr molecules. The column breakthrough volume and the amount adsorbed at breakthrough were smaller in tap versus distilled water. Carbon consumption was lower with activated carbon cloth than with the use of granular activated carbon.     

Adsorption of Cr(III) on ozonised activated carbon. Importance of Cpi-cation interactions

The adsorption of Cr(III) in aqueous solution was investigated on a series of ozonised activated carbons, analysing the effect of oxygenated surface groups on the adsorption process. A study was carried out to determine the adsorption isotherms and the influence of the pH on the adsorption of this metal. The adsorption capacity and affinity of the adsorbent for Cr(III) increased with the increase in oxygenated acid groups on the surface of the activated carbon. These findings imply that electrostatic-type interactions predominate in the adsorption process, although the adsorption of Cr(III) on the original (basic) carbon indicates that other forces also participate in the adsorption process. Thus, the ionic exchange of protons in the -Cpi-H3O(+) interaction for Cr(III) accounts for the adsorption of cationic species in basic carbons with positive charge density. Study of the influence of pH on the adsorption of Cr(III) showed that, in each system, the maximum adsorption occurred when the charge of the carbon surface was opposite that of the species of Cr(III) present at the pH of the experiment. These results confirmed that electrostatic interactions predominate in the adsorption process.     

Effects of activated carbon characteristics on the simultaneous adsorption of aqueous organic micropollutants and natural organic matter

The overall objective of this research was to determine the effects of physical and chemical activated carbon characteristics on the simultaneous adsorption of trace organic contaminants and natural organic matter (NOM). A matrix of 12 activated carbon fibers (ACFs) with three activation levels and four surface chemistry levels (acid-washed, oxidized, hydrogen-treated, and ammonia-treated) was studied to systematically evaluate pore structure and surface chemistry phenomena. Also, three commercially available granular activated carbons (GACs) were tested. The relatively hydrophilic fuel additive methyl tertiary-butyl ether (MTBE) and the relatively hydrophobic solvent trichloroethene (TCE) served as micropollutant probes. A comparison of adsorption isotherm data collected in the presence and absence of NOM showed that percent reductions of single-solute TCE and MTBE adsorption capacities that resulted from the presence of co-adsorbing NOM were not strongly affected by the chemical characteristics of activated carbons. However, hydrophobic carbons were more effective adsorbents for both TCE and MTBE than hydrophilic carbons because enhanced water adsorption on the latter interfered with the adsorption of micropollutants from solutions containing NOM. With respect to pore structure, activated carbons should exhibit a large volume of micropores with widths that are about 1.5 times the kinetic diameter of the target adsorbate. Furthermore, an effective adsorbent should possess a micropore size distribution that extends to widths that are approximately twice the kinetic diameter of the target adsorbate to prevent pore blockage/constriction as a result of NOM adsorption.     

Adsorption characteristics of clay adsorbents – sepiolite,kaolin and synthetic talc – for removal of Reactive Yellow 138:1

Adsorption characteristics of three clay adsorbents – sepiolite, kaolin and synthetic talc – were investigated to determine their applicability to remove an anionic reactive dye – Reactive Yellow 138:1 – from a water stream. Results showed that synthetic talc had the highest maximum monolayer adsorption capacity of 10.07 mg/g, followed by kaolin (3.73 mg/g) and sepiolite (3.23 mg/g), for the removal of Reactive Yellow 138:1. Synthetic talc and sepiolite removed dyes from aqueous solutions mainly through physical adsorption depending on the surface area. By contrast, the adsorption mechanism of kaolin was strongly influenced by the anion exchange mechanism. Zeta potential analysis revealed that the adsorption capacity of clay adsorbents increased under acidic rather than alkaline conditions, owing to protonation of the clay surface. Moreover, synthetic talc was successfully regenerated by heating at more than 400°C, effectively restoring its original adsorption capacity.     

Adsorption of phenol and reactive dye from aqueous solution on activated carbons derived from solid wastes

Activated carbons were produced from several solid wastes, namely, waste PET, waste tires, refuse derived fuel and wastes generated during lactic acid fermentation from garbage. Activated carbons having various pore size distributions were obtained by the conventional steam-activation method and via the pre-treatment method (i.e., mixture of raw materials with a metal salt, carbonization and acid treatment prior to steam-activation) that was proposed by the authors. The liquid-phase adsorption characteristics of organic compounds from aqueous solution on the activated carbons were determined to confirm the applicability of these carbons, where phenol and a reactive dye, Black5, were employed as representative adsorbates. The hydrophobic surface of the carbons prepared was also confirmed by water vapor adsorption. The characteristics of a typical commercial activated carbon were also measured and compared. It was found that the activated carbons with plentiful mesopores prepared from PET and waste tires had quite high adsorption capacity for large molecules. Therefore they are useful for wastewater treatment, especially, for removal of bulky adsorbates.     

Magnetic powder MnO-Fe2O3 composite--a novel material for the removal of azo-dye from water

Fine powder adsorbents or catalysts often show better adsorptive or catalytic properties, but they encounter the difficulties of separation and recovery in application. In this study, four inexpensive magnetic powder MnO-Fe2O3 composites used as adsorbent-catalyst materials were prepared and characterized. These materials could be recovered efficiently by a magnetic separation method. Their adsorptive properties for the removal of an azo-dye, acid red B (ARB), from water and the regeneration of adsorbents containing ARB by catalytic combustion was studied. These powder adsorbents showed excellent adsorption towards ARB under acidic conditions. A very fast adsorption rate was observed and could be well described by a pseudo-second-order kinetics model. The adsorption capacity increased with increasing Fe content and surface area of the adsorbent, and the highest adsorption capacity of 105.3 mg/g was obtained at pH 3.5. The adsorption was not affected by the presence of Cl-, but was significantly affected by SO4(2-). The adsorbent containing ARB can be regenerated by catalytic combustion of adsorbed ARB at 400 degrees C in air. Laboratory experiments demonstrated that this material is reusable.     

Removal of THM precursors by coagulation or ion exchange

The removal of natural organic matter (NOM) from drinking water supplies can be achieved by different processes, among them coagulation and adsorption. Synthetic waters made from concentrates of humic substances from reservoir and river waters were tested in the laboratory for ease of removal of NOM by coagulation with cationic organic polymers and with alum, and by adsorption on anion exchangers. For polymers such as high molecular weight polydiallyldimethylammonium chloride (polyDADMAC) and cationic polyacrylamides of high charge, performance was nearly as effective as alum, with colour removals 86–100% of those obtained for alum. Ion exchange using the best commercially available resins designed for this purpose, a gel polystyrene and a macroporous acrylic resin, was more effective than alum treatment for two of the natural waters studied, but inferior for a third. The resins were overall superior to cationic polymers.

The NOM was separated into four fractions based on hydrophobic and hydrophilic properties. Alum was not as effective as ion exchange for the elimination of individual ionic NOM fractions. It was better than cationic polymers for removal of humic and fulvic acids, although polyDADMAC was as good for one water. For the removal of charged compounds alum then polyDADMAC were the best performers for that water. Unequivocal evidence was obtained that coagulants remove material that is not adsorbed by resins, and vice versa. A combination of coagulation with a cationic polymer and adsorption by an anion exchanger removed essentially all of the NOM. The preference of the coagulants was for the larger, more hydrophobic molecules, and of resins for smaller highly charged hydrophilic molecules. Each fraction had trihalomethane formation potentials in the range 11–24 μg/mg, except for one water that was more reactive. Hence, the actual amount of each fraction in the original water becomes a crucial factor.     

Manganese-oxide-coated alumina: a promising sorbent for defluoridation of water

In this study, adsorption potential of a new sorbent manganese-oxide-coated alumina (MOCA) was investigated for defluoridation of drinking water using batch and continuous mode experiments. The effects of different parameters such as pH, initial fluoride concentration and co-existing ions (usually present in groundwater sample) were studied to understand the adsorption behavior of the sorbent under various conditions. Optimum removal of fluoride ions occurred in a pH range of 4-7. Results of the present study indicate that fluoride adsorption rate and adsorption capacity of MOCA are far superior to that of activated alumina (AA), which was used as the base material for MOCA preparation. The MOCA can be effectively regenerated using 2.5% NaOH as eluent. The Langmuir equilibrium model was found to be suitable for describing the fluoride sorption on AA and MOCA. The maximum fluoride uptake capacity for MOCA and AA was found to be 2.85 and 1.08 mg g(-1), respectively. The kinetic results showed that the fluoride sorption to MOCA followed pseudo--second-order kinetics with a correlation coefficient greater than 0.98. The fluoride sorption capacity at breakthrough point for both the adsorbents was greatly influenced by bed depth. A bed depth service time (BDST) approach was adopted to describe the continuous flow system. The batch and column studies demonstrated the superiority of MOCA over AA in removing fluoride from the drinking water system.     

Factors affecting the adsorption capacity of dissolved organic matter onto activated carbon: modified isotherm analysis

Effects of aqueous phase Ca(II) concentrations and pH levels on the adsorption capacity of dissolved organic matters (DOMs) as well as the capacity dependency on the sources and types of DOMs and activated carbons (ACs) were examined. The Ca(II) effect was studied for three coal-based ACs having different pore size distributions (PSDs) and for three DOMs contained in three water samples. For each water sample, four working solutions prepared by adding different dosages of Ca(II) (0-1.5 mM) were used. For the water sample whose adsorption capacity was least affected by Ca(II), the effect of pH was subsequently examined for four water pH levels (pH = 5.5-10) and these three ACs. Isotherm data were analyzed in terms of a modified isotherm model selected from three models developed for normalizing isotherms of heterogeneous organic mixtures. The Ca(II) effect depended obviously on the DOMs used. For all three ACs, increasing Ca(II) greatly enhanced the adsorption capacity of a commercial humic acid. However, the capacity of the DOM in a naturally colored surface water source was much less affected and that of the DOM remaining after precoagulation was not affected. The DOM-Ca(II) interactions, rather than the AC-Ca(II) interactions, seemed to be the predominant mechanism that controlled the extent of the Ca(II)'s impact. Water pH greatly affected the adsorption of the surface water DOM remaining after precoagulation. This effect seemed to be attributed to pH's capability in changing ACs' charge characteristics reflected by zeta-potentials. The adsorption capacity increased as the water pH decreased and was well correlated as a function of pH and the volume of AC pores in sizes of 30-100 A. ACs having more pores in this size region generally exhibited larger adsorption capacities.