Adsorption des acides humiques sur charbon active en poudre. Influence du triphosphate de sodiumAdsorption of humic acids onto powdered activated carbon. The influence of sodium triphosphate

The use of activated carbon beds for the removal of natural humic and fulvic substances found in water supplies, has recently received considerable attention in water treatment operation (Lee et al., 1980; Le Cloirec et al., 1983). Moreover, the use of carbon adsorption for the reduction of haloform precursors (Anderson et al., 1981) and trihalomethanes produced by chlorination process, has contributed to a comprehensive investigation of adsorption characteristics of natural organic compounds (McCreary and Snoeyink, 1981). Many recent works showed the influence of adsorption system characteristics, such as pH, salt type, salt concentration and ionic heterogeneity in multicomponent adsorption systems, on the removal efficiency of humic and fulvic substances by activated carbon (McCreary and Snoeyink, 1980; Randtke and Jepsen, 1982; Weber et al., 1983). The purpose of this study is to examine the effect of a main component of domestic detergents, sodium triphosphate (STP), on the adsorptive capacities of powdered activated carbon (PAC) for commercially supplied humic acids, at different pH values in distilled water. Also, the effect of STP concentration and pH on the adsorption affinity of the PAC for humic acids, is discussed in relation with electrokinetic properties of carbon particles (zeta potential measurements).A first batch equilibrium study (Figs 1 and 2), showed an effective enhancement of adsorption capacity for humic acids as a function of STP concentration, in a non buffered media (pH of distilled water, close to 5.0). For example, visible absorption analysis of humic acids indicates an increase of 93% (500 mg l^?1 PAC) and 133% (1000 mg l^?1 PAC) in the carbon adsorption efficiency for a STP concentration from 0.2 to 1.0mM. A second batch equilibrium study (Figs 3 and 4) led to adsorption isotherms for humic acids in distilled water, as a function of STP concentration and initial pH value of the non buffered multicomponent system. Freundlich isotherms showed an increase in the adsorption capacity of the PAC for humic acids, with a decrease in pH and an increase in STP concentration. However, the adsorption capacity for humic acids is quite reduced at high pH values in presence of STP, in comparison with results obtained with distilled water.Electrokinetic measurements on PAC suspensions (Fig. 5) indicates that both humic acids and STP induce a negative variation of the zeta potential of carbon particles. In such a binary system, the zeta potential is a linear function of the pH; the negative surface charge of the carbon increasing with an elevation of pH (Fig. 6). Therefore, it appears that some adsorption of triphosphate polyanion from solution could occur, contributing then to the apparent negative surface charge of PAC particles.It has been previously showed that the type of anion in sodium salts, had little effect on the enhancement of adsorptive capacities of activated carbon for humic substances (Lafrance and Mazet, 1985), due to Na⁺ ions. However, adsorption of TP anions on the carbon surface may produce a source of repulsive charges, unfavourable to the co-adsorption of humic acids as the pH of the binary system reach more basic conditions. The influence of possible electrostatic interactions between adsorbates at the carbon surface, on the adsorption efficiency for humic acids, could then be studied by zeta potential measurements of PAC particles during the adsorption process.     

Removal of organic matter from water by PAC/UF system

The laboratory-scale ultrafiltration (UF) experiments were conducted to determine the effect of the presence of powdered activated carbon (PAC) on the UF process performance, in terms of flux decline and the possibilities of membranes cleaning during backwashing. Poly(vinylidene fluoride) membranes formed by the phase inversion technique were used in the UF experiments. A model solution was prepared as a mixture of humic acids (HA) and phenol in concentration of 10 and 1 mg l(-1), respectively. Commercial powdered activated carbons CWZ 11 and CWZ 30 (Gryfskand Sp. z o. o., Hajnówka, Poland) were used as the adsorbents. PAC dosage was in the range of 10-100 mg PAC l(-1). The process was carried out in the cross-flow system. It was found that PAC addition to the distilled water leads to a small drop in the permeate flux, regardless of PAC dose and its type. Although PAC particles are too large to block the membrane pores inside, they deposit on the membrane surface and partially can plug the surface pores. The experimental results demonstrate that the backwashing process applied in combined PAC/UF system was especially effective when PAC dosages were <20mg PAC l(-1). However, a similar permeate flux was maintained for all carbon dosages used and reached the value of about 1 m3 m(-2) d(-1). Moreover, no further drop in the permeate flux for PAC addition to the solution containing foulants (HA) was observed. Effectiveness of the removal of HA and phenol from the model solutions was also investigated. In the PAC/UF system HA were removed in about 90%, whereas the complete removal of phenol was achieved for PAC dosage equal to 100 mg l(-1).     

TiO2 nanoparticles aggregation and disaggregation in presence of alginate and Suwannee River humic acids. pH and concentration effects on nanoparticle stability

The behavior of manufactured TiO₂ nanoparticles is studied in a systematic way in presence of alginate and Suwannee River humic acids at variable concentrations. TiO₂ nanoparticles aggregation, disaggregation and stabilization are investigated using dynamic light scattering and electrophoretic experiments allowing the measurement of z-average hydrodynamic diameters and zeta potential values. Stability of the TiO₂ nanoparticles is discussed by considering three pH-dependent electrostatic scenarios. In the first scenario, when pH is below the TiO₂ nanoparticle point of zero charge, nanoparticles exhibit a positively charged surface whereas alginate and Suwannee River humic acids are negatively charged. Fast adsorption at the TiO₂ nanoparticles occurs, promotes surface charge neutralization and aggregation. By increasing further alginate and Suwannee River humic acids concentrations charge inversion and stabilization of TiO₂ nanoparticles are obtained. In the second electrostatic scenario, at the surface charge neutralization pH, TiO₂ nanoparticles are rapidly forming aggregates. Adsorption of alginate and Suwannee River humic acids on aggregates leads to their partial fragmentation. In the third electrostatic scenario, when nanoparticles, alginate and Suwannee River humic acids are negatively charged, only a small amount of Suwannee River humic acids is adsorbed on TiO₂ nanoparticles surface. It is found that the fate and behavior of individual and aggregated TiO₂ nanoparticles in presence of environmental compounds are mainly driven by the complex interplay between electrostatic attractive and repulsive interactions, steric and van der Waals interactions, as well as concentration ratio. Results also suggest that environmental aquatic concentration ranges of humic acids and biopolymers largely modify the stability of aggregated or dispersed TiO₂ nanoparticles.     

Fe3O4 nano-particles prepared by co-precipitation method using local sands as a raw material and their application for humic acid removal

Magnetic Fe₃O₄ nano-particles were prepared successfully from commonplace sands as a raw material. The nano-particles were synthesized by chemical co-precipitation of high purity iron separated from commonplace sands through acidic leaching. The characterization of the synthesized nano-particles was performed using X-ray diffraction, fourier transform infrared, scanning electron microscopy, transmission electron microscopy, and potential zeta. Finally, the nano-particles were used for adsorption of humic acid (HA) from aqueous solutions using batch adsorption technique. The effects of pH, adsorbent dosage, agitation time, initial HA concentration, and temperatures on HA adsorption were evaluated. The adsorption of HA onto nano-particles followed the Sips isotherm and pseudo-second order kinetics models. Thermodynamic parameters data indicated that the HA adsorption process was non-spontaneous and endothermic under the experimental conditions. The adsorption of HA from peat water (the real sample) using the nano-particles demonstrated that they were an adsorbent with great potential for the removal of HA from peat water.     

受典型除草剂污染原水的应急处理工艺研究

以水中阿特拉津和莠灭净浓度突增为背景,研究了混凝、PAC吸附和PAC吸附＋混凝等工艺对它们的去除效率,同时根据原水水质的变化和水厂的常用工艺,分别考察了混凝剂投加量、pH值、预氧化对混凝去除阿特拉津和莠灭净的影响,以及目标物初始浓度、天然有机物浓度和预氧化对PAC吸附的影响。结果表明,调节pH值及采取预氧化措施均能改善混凝对阿特拉津和莠灭净的去除效果,但其出水浓度仍不能达标;天然有机物浓度对PAC吸附的影响并非是简单的线性关系,同时投加氧化剂和PAC会相互削弱其作用,PAC吸附＋混凝才是去除阿特拉津和莠灭净最简单、有效的方法。     

Simultaneous colour and DON removal from sewage treatment plant effluent: Alum coagulation of melanoidin

The aim of this study was to detect and characterise melanoidin in sewage treatment plant (STP) effluent, and to study the ability of alum coagulation to remove the colour and dissolved organic nitrogen (DON) associated with melanoidin. The melanoidin is non-biodegradable due to the complex cyclic based structure and thus it directly contributes to effluent nitrogen concentrations from the sewage treatment plant (STP). Lowering of effluent total nitrogen limits and the link between colour and chlorinated disinfection by-products have therefore driven a need to understand the structure, properties and treatability of DON species found in STP effluent.The focus of this paper is the refractory coloured, organic nitrogen compound melanoidin. Wetalla STP effluent has relatively high colour (170 mg-PtCo L⁻¹) and DON (2.5 mg L⁻¹) for a biological nutrient removal STP, owing to an industrial supply of melanoidin containing molasses fermentation wastewater. Alum coagulation jar tests were performed on synthetic melanoidin solution, STP effluent containing melanoidin (Wetalla, Toowoomba, Australia) and STP effluent free of melanoidin (Merrimac, Gold Coast, Australia) to examine the treatability of melanoidin and its associated colour and DON content when present in STP effluent.The removal of melanoidin from STP effluent resulted in significant colour and DON reduction. An alum dose of 30 mg L⁻¹ as aluminium was sufficient to reach maximum removal of colour (75%), DON (42%) and dissolved organic carbon (DOC) (30%) present in melanoidin containing STP effluent. Alum was shown to preferentially remove DON with a molecular weight >10 kDa over small molecular weight DON. Fluorescence excitation-emission matrix examination of the humic compounds present in the STP effluent indicated that melanoidin type humic compounds were more readily removed by alum coagulation than other humic compounds.     

粉末活性炭对内吸磷的吸附性能研究

研究了粉末活性炭对內吸磷的吸附去除效果以及吸附时间、活性炭投加量和水质条件对吸附效果的影响.结果表明,当內吸磷质量浓度为0.30 mg/L,活性炭投加量为20 mg/L时,在去离子水中吸附60 min后,出水內吸磷为0.02 mg/L;在去离子水中的吸附效果优于原水,在实际应用中需根据原水水质适当调整活性炭投加量或吸附...     

Humic acid adsorption and surface charge effects on schwertmannite and goethite in acid sulphate waters

In acid conditions, as in acid mine drainage waters, iron oxide particles are positively charged, attracting negatively charged organic particles present in surrounding natural waters. Schwertmannite (Fe8O8(OH)6SO4) and goethite (alpha-FeOOH) are the most typical iron oxide minerals found in mine effluents. We studied schwertmannite formation in the presence of humic acid. Further, surface charge and adsorption of humic acid on synthetic schwertmannite and goethite surfaces in pH 2-9 and in humic acid concentrations of 0.1-100 mg/L C were examined. Schwertmannite did precipitate despite the presence of humic acid, although it contained more sulphate and had higher specific surface area than ordinary schwertmannite. Specific surface area weighted results showed that schwertmannite and goethite had similar humic acid adsorption capacities. Sulphate was released from schwertmannite surfaces with increasing pH, resulting in an increase in specific surface area. Presence of sulphate in solution decreased the surface charge of schwertmannite and goethite similarly, causing coagulation. In acid conditions (pH 2-3.5), according to the zeta potential, schwertmannite is expected to coagulate even in the presence of high concentrations of humic acid (< or = 100 mg/L C). However, at high humic acid concentrations (10-100 mg/L C) with moderate acid conditions (pH>3.5), both schwertmannite and goethite surfaces are strongly negatively charged (zeta potential < -30 mV) thus posing a risk for colloid stabilization and colloidal transport.     

Photocatalytic inactivation of E. coli in surface water using immobilised nanoparticle TiO2 films

Photocatalysis is a promising method for the disinfection of potable water in developing countries where solar irradiation can be employed, thus reducing the cost of treatment. In addition to microbial contamination, water normally contains suspended solids, dissolved inorganic ions and organic compounds (mainly humic substances) which may affect the efficacy of solar photocatalysis. In this work the photocatalytic and photolytic inactivation rates of Escherichia coli using immobilised nanoparticle TiO₂ films were found to be significantly lower in surface water samples in comparison to distilled water. The presence of nitrate and sulphate anions spiked into distilled water resulted in a decrease in the rate of photocatalytic disinfection. The presence of humic acid, at the concentration found in the surface water, was found to have a more pronounced affect, significantly decreasing the rate of disinfection. Adjusting the initial pH of the water did not markedly affect the photocatalytic disinfection rate, within the narrow range studied.     

粉末活性炭对水中呋喃丹的吸附性能研究

考察了粉末活性炭吸附去除水中呋喃丹的可行性,并采用Freundlich公式拟合去离子水和自来水条件下的吸附等温方程.结果表明,采用粉末活性炭可有效去除水中的呋喃丹,在去离子水条件下,呋喃丹初始质量浓度为0.035 mg/L,投炭量为20 mg/L,吸附时间为120 min时,呋喃丹的去除率大于98％.根据吸附等温方程计...     

应对突发氯苯污染的粉末炭吸附工艺实验研究

考察了模拟常规工艺对水中氯苯的去除效能,测定了粉末炭(PAC)对原水中氯苯的吸附等温线和吸附动力学曲线,并采用Freundlich吸附等温式和假二级动力学模型进行拟合.结果表明,常规工艺难以有效去除水中氯苯;PAC可快速地吸附水中氯苯,5min吸附量可达平衡吸附量的80％以上,30 min吸附量可达98％以上.建立了P...     

Concentration of viruses from water on bituminous coal

The potential of bituminous coal for adsorption of viruses, using poliovirus as a model, was investigated. Influence of pH of water on the adsorption of viruses on a coal bed with and without addition of cation (Al³⁺) indicated that poliovirus could be adsorbed efficiently at pH 5 in presence of AlCl₃ at a concentration of 0.0005 M. Studies on the effect of different concentrations of monovalent, divalent and trivalent cations showed that the trivalent cation was more effective and was required at a lower concentration than other cations tested. A coal bed of 1.5 g could adsorb as high as 204,000 PFU from water based on the absence of virus in the filtrate. Total organic carbon content (TOC, 21–51 mg 1⁻¹) of the water did not interfere in virus adsorption to coal. The results obtained indicated that a bituminous coal bed could be used as one of the methods for efficient concentration of viruses from water.     

Assessing PAC contribution to the NOM fouling control in PAC/UF systems

This paper investigates the powdered activated carbon (PAC) contribution to the fouling control by natural organic matter (NOM) in PAC/UF hybrid process, as well as the foulant behaviour of the PAC itself. Solutions of NOM surrogates (humic acids, AHA, and tannic acid, TA) and AOM/EOM (algogenic organic matter/extracellular organic matter) fractions from a Microcystis aeruginosa culture were permeated through an ultrafiltration (UF) hollow-fibre cellulose acetate membrane (100 kDa cut-off). The greatest impairment on flux and the poorest rejection were associated with polysaccharide-like EOM substances combined with mono and multivalent ions. PAC, either in the absence or in the presence of NOM, did not affect the permeate flux nor the reversible membrane fouling, regardless of the NOM characteristics (hydrophobicity and protein content) and water inorganics. However, PAC controlled the irreversible membrane fouling, minimising the chemical cleaning frequency. Furthermore, PAC enhanced AHA and TA rejections and the overall removal of AOM, although it was apparently ineffective for the highly hydrophilic EOM compounds.     

Removal of organic micropollutants by coagulation and adsorption

The factors which affect removal of organic micropollutants by coagulation, sedimentation, filtration and activated carbon adsorption will be reviewed. Removal of specific compounds by coagulation, sedimentation and filtration is often slight, unless the pollutants adsorb on particles or associate with humic substances which are then coagulated. By comparison, removal of humic substances by these processes can be substantial, depending upon the water chemistry and the process conditions. Activated carbon may be applied in both the powdered (PAC) and granular (GAC) form. PAC and GAC have been used successfully throughout the world to remove odorous compounds. PAC has been used to a much smaller extent for removal of other micropollutants, but there is much potential for improvement of the application procedure so that good results can be achieved. GAC is widely used to remove micropollutants other than odor in Europe but has not been extensively used for this purpose in North America. The compounds which can be removed by GAC are presented and process monitoring procedures are discussed. Factors which limit its use include incomplete knowledge about which compounds must be removed and what effluent concentrations are acceptable.     

Adsorption of trihalomethanes from water with carbon nanotubes

Commercial carbon nanotubes (CNTs) were purified by acid solution and were employed as adsorbents to study adsorption of trihalomethanes (THMs) from water. The properties of CNTs such as purity, structure and nature of the surface were greatly improved after acid treatment which made CNTs become more hydrophilic and suitable for adsorption of low molecular weight and relatively polar THM molecules. The adsorption of THMs onto CNTs fluctuates very little in the pH range 3-7, but decreases with pH value as pH exceeds 7. A comparative study between CNTs and powdered activated carbon (PAC) for adsorption of THMs from water was also conducted. The short time needed to reach equilibrium as well as the high adsorption capacity of CHCl3, which accounts for a significant portion of THMs in the chlorinated drinking water, suggests that CNTs possess highly potential applications for THMs removal from water.     

粉末炭去除饮用水中土霉味物质的影响因素研究

采用粉末活性炭（PAC）去除饮用水中2-甲基异莰醇（MIB）、2,4,6-三氯茴萫醚（TCA）、2-异丙基-3-甲氧基吡嗪（IPMP）和2-异丁基-3-甲氧基吡嗪（IBMP）等4种常见的土霉味物质,研究了PAC种类、PAC投加量、嗅味物质的初始浓度、余氯、水质等因素对PAC去除土霉味物质的影响。结果表明,PAC吸附对嗅味物质的去除主要发生在前1 h内;煤质PAC对MIB有更高的去除率;在一定的吸附时间和活性炭投加量下,PAC对痕量嗅味物质的去除率与其初始浓度无关;余氯和有机物的存在降低了PAC对嗅味物质的吸附容量,水质对去除嗅味物质也有很大的影响。     

粉末活性炭去除水中石油类污染物的试验研究

以0#柴油为研究对象,考察了粉末活性炭对水中石油类污染物的吸附性能.结果表明,采用粉末活性炭可有效去除水中的石油类污染物,当柴油初始质量浓度为3 mg/L,吸附时间为30 min,投炭量为20 mg/L时,纯水及原水条件下柴油的去除率均大于70％,且在最大投炭量(80 mg/L)条件下,粉末活性炭可以应对在纯水和原水条...     

粉末活性炭对马拉硫磷的吸附性能研究

以马拉硫磷作为突发性污染物,考察了粉末活性炭对其的吸附效果。试验结果表明,粉末活性炭对纯水和滤后水中的马拉硫磷均具有较好的去除效果,对前者的去除效果更为明显,去除率随活性炭投加量的增加而升高。当马拉硫磷浓度为1.25 mg/L,纯水、滤后水中的活性炭投加量分别为12.0和20 mg/L时,反应120 min后马拉硫磷剩余浓度均低于0.25 mg/L。对滤后水而言,药剂费用约为0.06～0.08元/m3。     

Weak and strong acids in the surface waters of the tovdal region in S. Norway

The concentrations of weak and strong acids in surface waters of the Tovdal region of southern Norway were measured during a spring snow-melt period. The determinations were made by the pH titration method due to Gran. The strong acid concentrations in Tovdal river water varied between 3 and 11 μeq 1⁻¹, while the weak acid concentrations were between 62 and 106 μeq 1⁻¹ and the contribution of the weak acids to the hydrogen ion concentration ranged between 10 and 60%. The pH of the river water varied from 4.9 to 5.0 and in the absence of excess strong acid, the weak acids would have produced a pH of 5.2–5.3. The concentration of weak acids and their contribution to the hydrogen ion concentration were least during the period of most rapid thaw.No direct evidence of the nature of the weak acids was obtained, but routine chemical analysis data suggested that inorganic species derived from aluminium and silicon accounted for 40–60 μeq 1⁻¹, while 20–50 μeq 1⁻¹ were attributable to humic and fulvic acids. The titration characteristics of the weak acids could be approximated closely by a polybasic acid with a first ionization constant in the range 10⁻⁶ to 5 × 10⁻⁷ and less well defined weaker ionizations.Measurements on old snow containing coniferous tree litter and on melt water from a rocky barren contained weak acid concentrations comparable to the riverwater, indicating that only slight contact with vegetable matter or the ground is required to obtain significant concentrations of weak acids.     

Removal of 2,4,6-trichlorophenol and natural organic matter from water supplies using PAC in floc-blanket reactors

The objective of this study was to evaluate the addition of powdered activated carbon (PAC) to upflow floc-blanket reactors for the adsorption of natural and synthetic organic chemicals. A 15.5-1. bench-scale floc-blanket reactor was operated with PAC addition for the adsorption of 2,4,6-trichlorophenol (TCP) and natural organic matter from one groundwater and two surface waters under laboratory and field conditions, respectively. Influent TCP concentrations ranged from 21 to 415 μg/l. The PAC doses ranged from 2 to 12 mg/l. While the hydraulic residence time in the floc-blanket reactor varied from 15 to 30 min, the carbon residence time ranged from 9 to 34 h. This is due to the high solids concentration in the floc blanket, which ranged from 1200 to 8700 mg/l. Comparison between the extent of TCP adsorption through the floc-blanket reactor and the equilibrium adsorption isotherms of TCP on PAC showed that the maximum adsorption capacity of PAC for TCP was utilized in the reactor. However, this study showed that the maximum adsorptive capacity of the carbon in a continuous process is dependent on the influent adsorbate concentration. This was in agreement with isotherm studies conducted with varying initial TCP concentration. The maximum PAC adsorption capacity for natural organic matter was also achieved in the floc-blanket reactor.