Predictions of binary sorption isotherms for the sorption of heavy metals by pine bark using single isotherm data

The adsorption of three heavy metal ions by pine bark was studied. The study was divided into two parts; single component adsorption of the metals Cu2+, Cd2+ and Ni2+ and bisolute adsorption of the three binary systems Cu2+-Cd2+, Cu2+-Ni2+ and Cd2+-Ni2+. Extended Langmuir model, extended Freundlich model. Sips model and ideal adsorption solution theory (IAST) models were used to predict the equilibrium uptake for Cu2+, Cd2+ and Ni2+ in the binary diluted solutions using the single adsorption constants. The experimental data of single isotherm adsorption process were found to follow Langmuir isotherm model with less accuracy than Freundlich and Sips models. Whereas, the predictions of bisolute adsorption isotherms of the mentioned three systems, Cu2+-Cd2+, Cu2+-Ni2+ and Cd2+-Ni2+, showed good agreement with experimental data when using Extended-Langmuir, Extended-Freundlich and IAST. However, the only good fit of the Sips model was with the Cu2+-Cd2+ system.     

Aquatic macrophytes potential for the simultaneous removal of heavy metals (Buenos Aires, Argentina)

Heavy metal removal from water has been approached by using different technologies. Phytotechnologies, with an increasing development during the last two decades, involve using plants for metal removal. Three autochthonous floating macrophytes, common in pampean shallow lakes (Argentina), Pista stratiotes, Spirodela intermedia and Lemna minor were used in laboratory experiences for the simultaneously removal of several heavy metals (Fe, Cu, Zn, Mn, Cr and Pb) resulting from anthropogenic activity, in order to simulate a naturally polluted environment. The experiences were performed for different concentrations of metals along 15 days. High metal removal percentages were obtained for the 3 species and metals. L. minor did not survive the conditions of the experiment. High correlation between the final water and the macrophytes metal concentration was obtained, deviations were due to PbCrO(4) precipitation. The rate of metal uptake was dependent on the metal concentration for the 3 species studied.     

4A沸石对复合污染水体中Pb2+、Cu2+和Cd2+的去除

采用静态吸附法以4A沸石为吸附剂研究其对复合污染水体中Pb2+、Cu2+和Cd2+的竞争吸附特性,并探讨了影响吸附的环境因素。实验表明,在室温条件下,溶液pH5～6,4A沸石15 mg对10 mL复合污染溶液(Pb2+、Cu2+和Cd2+浓度分别为100 mg/L)吸附20 min时,对溶液中3种重金属的吸附去除率均可达99.8%以上。反应过程中4A沸石对3种重金属的吸附速率大小为Pb2+>Cu2+>Cd2+。复合污染水体中4A沸石对Pb2+、Cu2+和Cd2+的吸附符合Langmuir和Fre-undlich等温吸附方程,相关系数分别为0.9981、0.9901、0.9916和0.9638、0.9194、0.9689。经计算,4A沸石对Pb2+、Cu2+和Cd2+的饱和吸附量分别为129.9 mg/g、107.5 mg/g和99.0 mg/g。4A沸石吸附重金属离子达到吸附平衡的时间较短,对溶液pH值的适应性较好。吸附后的4A沸石可以再生利用,对铅离子洗脱重复利用性较铜离子和镉离子强。     

皂化改性橘子皮生物吸附剂对重金属离子的吸附

以生物废料橘子皮(OP)为原料,经乙醇、氢氧化钠处理,得到改性橘子皮生物吸附剂SOP,将其用于对重金属离子Cu2+、Pb2+、Cd2+、Zn2+和Ni2+的吸附。研究了溶液pH、吸附时间和重金属离子初始浓度对SOP吸附性能的影响。结果表明,重金属离子在生物吸附剂上的吸附速率快,符合准二级动力学方程。SOP对重金属离子的吸附等温线符合Lang-muir模型,根据Langmuir模型计算SOP对Cu2+、Pb2+、Cd2+、Zn2+和Ni2+的饱和吸附量分别为56.82、152.4、66.27、33.90和23.02 mg/g,均高于改性前。常见阳离子的存在对重金属离子吸附的影响较小,改性后的橘子皮生物吸附剂可以再生重复使用4次以上,是性能良好的重金属离子吸附剂。     

Cadmium and chromium removal kinetics from solution by two aquatic macrophytes

The aim of this work was to determine chromium and cadmium bioaccumulation processes of two free-floating macrophytes commonly used in wetlands for water treatment: Salvinia herzogii and Pistia stratiotes. Metal removal from the solution involves two stages: a fast one and a slow one. The fast stage of the Cd uptake is significantly different for each species, while it is not significantly different in Cr uptake. The most important processes of Cd uptake are biological ones in S. herzogii and adsorption, chelation and ionic exchange are in P. stratiotes. The main processes of Cr uptake in both macrophytes are adsorption, chelation and ion exchange. The slow stage is different for each species and metal. Cr precipitation induced by roots occurs in P. stratiotes. Cr uptake through leaves is probably the main cause of the increase of Cr in the aerial parts of S. herzogii.     

A comparative study on metal sorption by brown seaweed

This study compared the sorption of Ag, Cd, Co, Cd, Mn, Ni, Pb and Zn by a Ca-treated Sargassum biomass at pH 5.0, under low and high ionic strength (IS) conditions. The sorption isotherms of As [As(V)] and Cr [Cr(III) and Cr(VI)] were also determined at low IS. The isotherm data for the eight cationic metals and Cr(III) were well fitted by Langmuir equations. Generally, the maximum metal uptake (Umax) followed: Cr(III) > Pb approximately Cu > Ag approximately Zn approximately Cd > Ni approximately Mn approximately Co > Cr(VI) > As(V) at low IS and Pb > Cu > Co > Mn approximately Cd > Zn approximately Ag > Ni at high IS. As(V) did not bind to the seaweed at pH 5.0. The results indicated that sorption of Pb was not affected by the increasing IS, though the percentage of free Pb ions in the water was greatly reduced as predicted by the speciation model. High IS lowered Umax by 10-36% (except Co and Pb), and lowered the affinity constant of the metal by 33-91% for all cationic metals, as compared to low IS. Moreover, the removal efficiency of the cationic metals and Cr decreased exponentially with initial metal concentrations and was lower at high IS. Ion-exchange was the mechanism responsible for the cationic metal sorption onto the seaweed, and Na ion interfered with the cationic metal binding through electrostatic interaction. In conclusion, this study showed the differential binding capacity of the Sargassm biomass for different metals and oxidation states and the differential effects of IS. According to the present results, Sargassum may be considered a good biosorbent for cationic metals (especially Pb) in both low and high-salt containing wastewater.     

Evaluation of pectin binding of heavy metal ions in aqueous solutions

Evaluation of adsorption performance of several industrially manufactured pectins towards some toxic heavy metals was carried out. Adsorption isotherms for divalent cations in simulant aqueous solutions were measured and corresponding distribution coefficients were calculated. The following selectivity sequences we found for pectins: Pb2+ > Cu2+ > Co2+ > Ni2+ > Zn2+ > Cd2+. It was shown that a beet pectin exhibits a high affinity for Pb2+ and Cu2+ ions, an apple pectin for Co2+ ion and a citrus pectin for Ni2+ ion. The binding properties of all pectins towards Zn2+ and Cd2+ ions are extremely poor. The quantitative data on adsorption performance of pectins suggest their applicability as food additives or remedies for efficient removal of Pb2+, Cu2+, Co2+, and Ni2+ ions from different biological systems, including human and animal organisms.     

可渗透反应复合电极法对土壤重金属的电动去除

将零价铁(Fe0)、沸石等活性材料附着在电极上形成可渗透反应层并构成可渗透反应复合电极,采用不同的复合电极对Cd2+、Ni 2+、Pb2+和Cu2+等4种阳离子型重金属污染土壤进行了电动力学修复。研究了不同可渗透反应复合电极对土壤pH的控制效果以及对重金属的去除作用,分析了迁移到复合电极中的重金属形态变化。结果表明,复合电极中添加酸、碱性沸石并适时更换,可有效中和、截留阴阳极电解产生的OH-和H+,避免或减缓土壤酸碱迁移带的形成,防止重金属离子的过早沉淀及土壤过度酸化,极大提高了重金属的去除率。复合电极中Fe0可将迁移进来的重金属离子进行还原稳定,实现重金属污染物的捕获与固定,与迁移到沸石复合电极中的4种重金属不稳定态相比,"Fe0+沸石"复合电极中重金属不稳定态分别下降了61.4、60.5、61.4、57.1百分点。结果还显示,阴极采用"Fe0+沸石"复合电极并适时进行更换,施加1.5V/cm的直流电压修复10d后,土壤中Cd、Ni、Pb、Cu的总去除率分别为44.5%、41.5%、33.5%和36.7%,且进一步延长修复时间和持续更换电极可获得更为理想的修复效果。     

组合式水生植物净化系统对Cu、Pb和Cd的去除与生物富集特征

选取再力花、美人蕉、水烛、旱伞草、梭鱼草、慈姑、菖蒲、水葫芦和大藻9种植物作为实验植物,构建成以高效净化重金属污染水体为主要功能的组合式水生植物高效净化系统（人工湿地＋生态浮床＋水生植物塘3个处理单元串联而成）,研究不同处理单元中水生植物对重金属Cu、Pb和cd的去除能力及富集特征。结果表明,该净化系统经过为期60d的连续运行,对Cu、Pb和Cd的去除率较为稳定,可分别达到Cu93．5％～96．1％、Ph94．5％～95．2％和Cd95．6％～97．4％,3种重金属出水浓度均可达到GB3838-2002Ⅲ类水排放要求;其中人工湿地单元对重金属去除贡献率最高,Cu、Pb和Cd分别为54．15％、33．61％和44．84％,其次为生态浮床处理单元,Cu、Pb和Cd的去除贡献率分别为38．61％、51．42％和38．56％,而水生植物塘主要起到深度处理作用,对Cu、Pb和cd的去除贡献率分别为7．24％、14．97％和16．6％。9种植物在系统运行期间,生长状况良好,且重金属累积量较高,尤其是生物塘系统中的水葫芦和大藻,实验期间其重金属生物富集系数（BCF）均在200以上。所选植物不同部位对3种重金属的吸收富集能力均表现为根最强。     

组合式水生植物净化系统对Cu、Pb和Cd的去除与生物富集特征

选取再力花、美人蕉、水烛、旱伞草、梭鱼草、慈姑、菖蒲、水葫芦和大薸9种植物作为实验植物,构建成以高效净化重金属污染水体为主要功能的组合式水生植物高效净化系统(人工湿地+生态浮床+水生植物塘3个处理单元串联而成),研究不同处理单元中水生植物对重金属Cu、Pb和Cd的去除能力及富集特征。结果表明,该净化系统经过为期60 d的连续运行,对Cu、Pb和Cd的去除率较为稳定,可分别达到Cu 93.5%~96.1%、Pb 94.5%~95.2%和Cd 95.6%~97.4%,3种重金属出水浓度均可达到GB3838-2002Ⅲ类水排放要求;其中人工湿地单元对重金属去除贡献率最高,Cu、Pb和Cd分别为54.15%、33.61%和44.84%,其次为生态浮床处理单元,Cu、Pb和Cd的去除贡献率分别为38.61%、51.42%和38.56%,而水生植物塘主要起到深度处理作用,对Cu、Pb和Cd的去除贡献率分别为7.24%、14.97%和16.6%。9种植物在系统运行期间,生长状况良好,且重金属累积量较高,尤其是生物塘系统中的水葫芦和大薸,实验期间其重金属生物富集系数(BCF)均在200以上。所选植物不同部位对3种重金属的吸收富集能力均表现为根最强。     

Physico-chemical characteristics and pollution level of Lake Nainital (U.P., India): role of macrophytes and phytoplankton in biomonitoring and phytoremediation of toxic metal ions

Lake Nainital is the sole source of drinking water for the local people and even to majority of tourists. In background of lake utility and its importance at national level, such study is essential which is focused on toxic metal pollution and current nutrient status of the lake and their magnification by algae and macrophytes. Study has shown that lake water is rich in nutrients which supports growth of many aquatic macrophytes and algal blooms. Besides, water is contaminated with metals like Cr, Cu, Fe, Mn, Ni, Pb and Zn. Concentration of some of them like Fe, Pb and Ni were higher than the recommended maximum permissible limits. Concentration of these metals were also found high in lake sediments. The level of metals amongst various components of lake varied considerably in different season. Plants and algae growing therein accumulated appreciable amount of metals and water roots of Salix being more efficient than others. High metal removing potential of these plants may be significant for biomonitoring studies and could be a useful phytoremediation technology to restore water quality by harvesting submerged and floating biomass inhabiting littoral zone of the lake.     

Competitive adsorption characteristics of Co2+, Ni2+, and Cr3+ by IRN-77 cation exchange resin in synthesized wastewater

Adsorption properties of Co2+, Ni2+, and Cr3+ on an Amberlite IRN-77 cation exchange resin were investigated in batch systems. Levels of adsorption rapidly approached an equilibrium state within 1 h. The adsorption characteristics of each metal onto the resin were accurately represented by Langmuir isotherms. Co2+ and Ni2+, which have an equivalent electrovalence, displayed similar levels of adsorption onto the resin when they coexisted in the solution. However, when Cr3+ was added to the solution it competitively replaced Co2+ and Ni2+ ions that had been previously adsorbed onto the resin, resulting in the desorption of these metals into the solution. The result was likely due to a higher adsorption affinity of Cr3+ relative to Co2+ and Ni2+. This implies that interactively competitive adsorption of multi-cations onto the resin should be thoroughly considered when contemplating the efficient operation of an ion exchange process in the treatment of industrial wastewater.     

Characterization of Cd-, Pb-, Zn-resistant endophytic Lasiodiplodia sp. MXSF31 from metal accumulating Portulaca oleracea and its potential in promoting the growth of rape in metal-contaminated soils

The aim of this study was to characterize the features of a Cd-, Pb-, and Zn-resistant endophytic fungus Lasiodiplodia sp. MXSF31 and to investigate the potential of MXSF31 to remove metals from contaminated water and soils. The endophytic fungus was isolated from the stem of Portulaca oleracea growing in metal-contaminated soils. The maximum biosorption capacities of MXSF31 were 3.0?×?10³, 1.1?×?10⁴, and 1.3?×?10⁴ mg kg^?1 for Cd, Pb, and Zn, respectively. The biosorption processes of Cd, Pb, and Zn by MXSF31 were well characterized with the pseudo-second-order kinetic model. The biosorption isotherm processes of Pb and Zn by the fungus were fitted better with the Langmuir model, while the biosorption processes of Cd was better fitted with the Freundlich model. The biosorption process of MXSF31 was attributed to the functional groups of hydroxyl, amino, carbonyl, and benzene ring on the cell wall. The active biomass of the strain removed more Cd, Pb, and Zn (4.6?×?10⁴, 5.6?×?10⁵, and 7.0?×?10⁴ mg kg^?1, respectively) than the dead biomass. The inoculation of MXSF31 increased the biomass of rape (Brassica napus L.), the translocation factor of Cd, and the extraction amount of Cd by rape in the Cd?+?Pb-contaminated soils. The results indicated that the endophytic fungus strain had the potential to remove heavy metals from water and soils contaminated by multiple heavy metals, and plants accumulating multiple metals might harbor diverse fungi suitable for bioremediation of contaminated media.     

Competitive sorption of heavy metal by soils. Isotherms and fractional factorial experiments

Competing ions strongly affect heavy metal sorption onto the solid surfaces of soil. This study evaluated competitive sorption of Cd, Cu, Ni, Pb and Zn on three soils: Calcixerollic Xerochrept, Paralithic Xerorthent and Lithic Haplumbrept. Monometal and competitive sorption isotherms were obtained at 25 degrees C. The individual effect of ions on retention of the others was ascertained by a fractional factorial analysis design. Most of the sorption isotherms belonged to type L subtype 2 in the classification of Giles. In competitive sorption the initial linear part was shorter and the knee sharper when compared with monometal sorption isotherms. Parameters related to sorptive capacity, such as Point B, Langmuir monolayer and Freundlich distribution coefficient, were higher in monometal than in competitive sorption, and in basic soils than in acidic soil. Calcium desorbed at different points of the sorption isotherms indicated that cationic exchange with Ca was the main retention mechanism in calcareous soils. For Pb, the ratio Ca desorbed/Pb sorbed was close to one; for Cu, Ni and Zn the ratio ranged from 1.20 to 1.37, probably due to partial dissolution of calcium carbonates by hydrolytic processes during retention. On the other hand, Cd had a ratio around 0.6 reflecting another additional retention mechanism, probably surface complexation. Fractional factorial design confirmed that the presence of the cations investigated reduced the amount of the five metals retained, but the presence of Cu and Pb in the system depressed Ni, Cd and Zn sorption more than the inverse. Cation mobility was enhanced when equilibrium concentration increased and the effect was higher in Ca-saturated soils.     

Biosurfactant technology for remediation of cadmium and lead contaminated soils

This research focuses on column experiments conducted to evaluate the potential of environmentally compatible rhamnolipid biosurfactant produced by Pseudomonas aeruginosa strain BS2 to remove heavy metals (Cd and Pb) from artificially contaminated soil. Results have shown that di-rhamnolipid removes not only the leachable or available fraction of Cd and Pb but also the bound metals as compared to tap water which removed the mobile fraction only. Washing of contaminated soil with tap water revealed that approximately 2.7% of Cd and 9.8% of Pb in contaminated soil was in freely available or weakly bound forms whereas washing with rhamnolipid removed 92% of Cd and 88% of Pb after 36 h of leaching. This indicated that di-rhamnolipid selectively favours mobilization of metals in the order of Cd>Pb. Biosurfactant specificity observed towards specific metal will help in preferential elution of specific contaminant using di-rhamnolipid. It was further observed that pH of the leachates collected from heavy metal contaminated soil column treated with di-rhamnolipid solution was low (6.60-6.78) as compared to that of leachates from heavy metal contaminated soil column treated with tap water (pH 6.90-7.25), which showed high dissolution of metal species from the contaminated soil and effective leaching of metals with treatment with biosurfactant. The microbial population of the contaminated soil was increased after removal of metals by biosurfactant indicating the decrease of toxicity of metals to soil microflora. This study shows that biosurfactant technology can be an effective and nondestructive method for bioremediation of cadmium and lead contaminated soil.     

氢氧化镁处理含镍废水的研究

考察了氢氧化镁用量、搅拌时间、温度及pH对处理效果的影响 ,初步探讨了吸附作用机理。结果表明 :氢氧化镁对镍离子具有较强的吸附性能 ,去除率可达 99%以上。吸附等温线符合Langmuir模式 ,饱和吸附量 17.5 7mg/g。含Cd2 +、Ni2 +和Pb2 +的电镀废水经氢氧化镁吸附后 ,出水达到国家排放标准。     

Effect of dissolved metal ions on PCE decomposition by gamma-rays

This study investigates the effect of initial tetrachloroethylene (PCE) concentration, irradiation dose and dissolved metal ions such as Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+ on removal of PCE by gamma irradiation. The amount of removed PCE decreased with increase in initial PCE concentration and increased with increase in irradiation dose. PCE removal reached a maximum in the presence of Fe3+, while Cu2+ strongly hindered PCE decomposition. Except for Cu2+, the amount of removed PCE in the presence of metal ions was linearly dependent on the standard reduction potential of the metal ions. The extraordinary inhibition of Cu2+ in PCE removal was caused by the action of Cu2+ as a strong *OH scavenger, that was directly confirmed by electron paramagnetic resonance spectroscopy.     

A comparative investigation on the biosorption of lead by filamentous fungal biomass

The removal of lead from aqueous solutions by adsorption on filamentous fungal biomass was studied. Batch biosorption experiments were performed to screen a series of selected fungal strains for effective lead removal at different metal and biomass concentrations. Biosorption of the Pb²⁺ ions was strongly affected by pH. The fungal biomass exhibited the highest lead adsorption capacity at pH 6. Isotherms for the biosorption of lead on fungal biomass were developed and the equilibrium data fitted well to the Langmuir isotherm model. At pH 6, the maximum lead biosorption capacity of Mucor rouxii estimated with the Langmuir model was 769 mg/g dry biomass, significantly higher than that of most microorganisms. Biomass of Mucor rouxii showed specific selectivity for Pb²⁺ over other metals ions such as Zn²⁺. Ni²⁺ and Cu²⁺. This fungal strain may be applied to develop potentially cost-effective biosorbent for removing lead from effluents. The technique of scanning electron microscopy coupled with X-ray dispersion analysis shows that Pb²⁺ has exchanged with K⁺ and Ca²⁺ on the cell wall of Mucor rouxii, thereby suggesting ion exchange as one of the dominant mechanisms of metal biosorption for this fungal strain.     

Sorption kinetics and leachability of heavy metal from the contaminated soil amended with immobilizing agent (humus soil and hydroxyapatite)

Release of heavy metals onto the soil as a result of agricultural and industrial activities may pose a serious threat to the environment. This study investigated the kinetics of sorption of heavy metals on the non-humus soil amended with (1:3) humus soil and 1% hydroxyapatite used for in situ immobilization and leachability of heavy metals from these soils. For this, a batch equilibrium experiment was performed to evaluate metal sorption in the presence of 0.05 M KNO(3) background electrolyte solutions. The Langmuir isotherms applied for sorption studies showed that the amount of metal sorbed on the amended soil decreased in the order of Pb(2+)>Zn(2+)>Cd(2+). The data suggested the possibility of immobilization of Pb due to sorption process and immobilization of Zn and Cd by other processes like co-precipitation and ion exchange. The sorption kinetics data showed the pseudo-second-order reaction kinetics rather than pseudo-first-order kinetics. Leachability study was performed at various pHs (ranging from 3 to 10). Leachability rate was slowest for the Pb(2+) followed by Zn(2+) and Cd(2+). Out of the metal adsorbed on the soil only 6.1-21.6% of Pb, 7.3-39% of Zn and 9.3-44.3% of Cd leached out from the amended soil.     

Metals in bulk deposition and surface waters at two upland locations in northern England

Concentrations of aluminium and minor metals (Mn, Ni, Cu, Zn, Sr, Cd, Ba, Pb) were measured in precipitation and surface water at two upland locations (Upper Duddon Valley, UDV; Great Dun Fell, GDF) in northern England for 1 year commencing April 1998. At both locations, the loads in bulk precipitation were at the lower ends of ranges reported for other rural and remote sites, for the period 1985-1995. The deposited metals were mostly in the dissolved form, and their concentrations tended to be greatest when rainfall volumes were low. The concentrations of Cu, Zn and Pb in deposition were correlated (r2 > or = 0.40) with concentrations of non-marine sulphate. Three streams, ranging in mean pH from 5.07 to 7.07, and with mean concentrations of dissolved organic carbon (DOC) < 1 mg l(-1). were monitored at UDV, and two pools (mean pH 4.89 and 6.83, mean DOC 22 and 15 mg l(-1)) at GDF. Aluminium and the minor metals were mainly in the dissolved form, and in the following ranges (means of 49-51 samples. microg l(-1)): Al 36-530. Mn 4.4-36, Ni 0.26-2.8, Cu 0.25-1.7, Zn 2.1-30, Cd 0.03-0.16, Ba 1.9-140, Pb 0.10-4.5. Concentrations were generally higher at GDF. Differences in metal concentrations between the two locations and between waters at each location, and temporal variations in individual waters, can be explained qualitatively in terms of sorption to solid-phase soil organic matter and mineral surfaces, complexation and transport by DOC, and chemical weathering. The UDV catchments are sinks for Pb and sources of Al, Mn, Sr, Cd and Ba. The GDF catchments are sources of Al, Mn, Ni, Zn, Sr, Cd and Ba. Other metals measured at the two locations are approximately in balance. Comparison of metal:silicon ratios in the surface waters with values for silicate rocks indicates enrichment of Ni and Cu, and substantial enrichment of Zn, Cd and Pb. These enrichments, together with high metal deposition in the past, make it likely that concentrations of the metals in the surface waters are governed by release from catchment pools of atmospherically-deposited metal. The catchments appear to be responding on a time scale of decades, possibly centuries, to changes in metal deposition. For the more acid waters at UDV, the calculated free-ion concentrations of Al are similar to published LC50 values for acute toxicity towards fish. The free-ion concentrations of Ni, Cu, Zn and Cd in all the surface waters are one-to-four orders of magnitude lower than reported LC50 values for fish.