Improvement of metal adsorption onto chitosan/Sargassum sp. composite sorbent by an innovative ion-imprint technology

Technology for immobilization of biomass has attracted a great interest due to the high sorption capacity of biomass for sequestration of toxic metals from industrial effluents. However, the currently practiced immobilization methods normally reduce the metal sorption capacities. In this study, an innovative ion-imprint technology was developed to overcome the drawback. Copper ion was first imprinted onto the functional groups of chitosan that formed a pellet-typed sorbent through the granulation with Sargassum sp.; the imprinted copper ion was chemically detached from the sorbent, leading to the formation of a novel copper ion-imprinted chitosan/Sargassum sp. (CICS) composite adsorbent. The copper sorption on CICS was found to be highly pH-dependent and the maximum uptake capacity was achieved at pH 4.7-5.5. The adsorption isotherm study showed the maximum sorption capacity of CICS of 1.08 mmol/g, much higher than the non-imprinted chitosan/Sargassum sp. sorbent (NICS) (0.49 mmol/g). The used sorbent was reusable after being regenerated through desorption. The FTIR and XPS studies revealed that the greater sorption of heavy metal was attributed to the large number of primary amine groups available on the surfaces of the ion-imprinted chitosan and the abundant carboxyl groups on Sargassum sp. Finally, an intraparticle surface diffusion controlled model well described the sorption history of the sorbents.     

Sorption of cadmium(II) and zinc(II) ions from aqueous solutions by cassava waste biomass (Manihot sculenta Cranz)

The sorption of two divalent metal ions, Cd(II) and Zn(II), onto untreated and differentially acid-treated cassava waste biomass over a wide range of reaction conditions was studied at 30°C. The metal ion removal from the spent biomass was also measured. The batch experiments show that pH 4.5–5.5 was the best range for the sorption of the metal ions for untreated and acid-treated biomass. Time-dependent experiments for the metal ions showed that for the two metals examined, binding to the cassava waste biomass was rapid and occurred within 30 min and completed within 1 h. High sorption capacities were observed for the two metals. The binding capacity experiments revealed the following amounts of metal ions bound per gram of biomass: 86.68 mg/g Cd, 55.82 mg/g Zn and 647.48 mg/g Cd, 559.74 mg/g Zn for untreated and acid-treated biomass, respectively. It was further found that the rate of sorption was particle-diffusion controlled, and the sorption rate coefficients were determined to be 2.30×10⁻¹ min⁻¹ (Cd²⁺), 4.0×10⁻³ min⁻¹ (Zn²⁺) and 1.09×10⁻¹ min⁻¹ (Cd²⁺), 3.67×10⁻² min⁻¹ (Zn²⁺) for 0.5 and 1.00 M differential acid treatment, respectively. Desorption studies showed that acid treatment inhibited effective recovery of metal ions already bound to the biomass as a result of stronger sulfhydryl-metal bonds formed. Less than 25% of both metals were desorbed as concentration of acid treating reagent increases. However, over 60% Cd and 40% Zn were recovered from untreated biomass during the desorption study. The results from these studies indicated that both untreated and acid-treated cassava waste biomass could be employed in the removal of toxic and valuable metals from industrial effluents.     

Uptake of heavy metals from synthetic aqueous solutions using modified PEI-silica gels

The decontamination of synthetic Pb(II), Zn(II), Cd(II), Ni(II) solutions was investigated, using silica gels chemically modified with poly(ethyleneimine) (PEI) as sorbents. Two families of sorbents, i.e. silica/PEI and crosslinked silica/PEI, were prepared and characterized. Then the removal of metal ions from synthetic aqueous solutions was studied by static tests. They revealed that the sorption capacities depend on the pH, the initial concentration and to some extent on the nature of the metal. The recovery of the metal cations from the saturated sorbents was possible with diluted acid, only for the crosslinked supports. In this case, the regeneration and reuse without sorption decrease, was demonstrated. The presence of other cations (as Na(+), Ca(2+)) and metals does not affect the sorption capacities.     

Removal of copper and nickel ions from aqueous solutions by grape stalks wastes

In the present work, the usefulness of grape stalks wastes generated in the wine production process has been investigated for the removal of copper and nickel ions from aqueous solutions. The sorption process was relatively fast and equilibrium was reached after about 60 min of contact. The influence of pH, sodium chloride and metal concentration on metal removal has been studied. Uptake showed a pH-dependent profile. Maximum sorption for both metals was found to occur at around pH 5.5-6.0. An increase of sodium chloride concentration caused a decrease in metal removal. Langmuir isotherms, at pH 6.0, for each metal were used to describe sorption equilibrium data. Maximum uptake obtained was 1.59x10(-4) mol of copper and 1.81x10(-4) mol of nickel per gram of dry sorbent. Sorption of copper and nickel on grape stalks released an equivalent amount of alkaline and alkaline earth metals (K+, Mg2+, Ca2+) and protons, indicating that ionic exchange is predominantly responsible for metal ion uptake. Fourier transform infrared (FTIR) spectrometry analysis indicated that lignin C-O bond might be involved in metal uptake. Equilibrium batch sorption studies were also performed using a two metal system containing (Cu(II)+Ni(II)). In the evaluation of the two metal sorption system performance, single isotherm curves had to be replaced by three-dimensional sorption isotherm surface. In order to describe the isotherm surface mathematically, the extended-Langmuir model was used. Nickel was found to be much more sensitive to the presence of copper than copper is to the presence of nickel.     

Biosorption of mercury and lead by dried Aspergillus niger Tiegh. isolated from estuarine sediments

The sorption of Hg and Pb from mono‐metal and bi‐metal solution under different concentrations (20ppm–80ppm) was studied using dried Aspergillus niger biomass. The biosorption of Hg and Pb from the mono‐metal solution was found to be much better than from the bi‐metal solution. The maximum sorption of heavy metals was observed at pH 5–6 and at temperature 25°C–26°C. Biosorption of heavy metals from mono‐metal and bi‐metal solutions followed the Langmuir and Freundlich isotherm. The role of different functional groups like amine, hydroxyl, carboxyl and the phosphate group was confirmed by FTIR. The adsorption of metal ions on the biomass surface and the possible ion exchange mechanism was confirmed using SEM‐EDAX studies. A. niger can be used as a good biosorption agent for removing Hg and Pb from aqueous solution when present individually or in combination.     

Bioaccumulation of copper(II) and nickel(II) by the non-adapted and adapted growing Candida sp

The effect of copper(II) and nickel(II) ions on the growth and bioaccumulation properties of non-adapted and adapted growing cells of a non-pathogenic Candida sp. has been tested under laboratory conditions as a function of initial pH and initial metal ion concentration. Optimum pH value for maximum metal ion accumulation was determined as 4.0 for both the metal ions. Although the copper(II) adapted Candida sp. was capable of removing of copper(II) with the maximum specific uptake capacity of 36.9 mg g-1 at 783.6 mg dm-3 initial copper(II) concentration, non-adapted Candida was only capable of bioaccumulating copper(II) with 23.1 mg g-1 maximum uptake capacity from aqueous solution at 578.7 mg dm-3 initial copper(II) concentration. The non-adapted and nickel(II) adapted Candida cells also showed the highest nickel(II) uptake capacities (46.8 and 30.8 mg g-1, respectively) at 321.5 and 300.6 mg dm-3 initial nickel(II) concentrations, respectively. For both the non-adapted and nickel(II) adapted Candida sp., the growth of cells was totally inhibited by 500 mg dm-3 of nickel(II) ions. The results also indicated that copper(II) adapted Candida sp. has been found to be more efficient to accumulate larger amounts of copper(II) than that of nickel(II) bioaccumulated by nickel(II) adapted Candida at higher initial metal ion concentrations without loosing its biological activity.     

Film-pore diffusion modeling for the sorption of metal ions from aqueous effluents onto peat

The sorption of three metal ions, namely, copper, nickel and lead onto sphagnum peat moss has been studied using an agitated batch sorber system. The equilibrium isotherms were determined and kinetic runs were performed over a range of concentrations for each metal ion. A film-pore diffusion mass transfer model has been developed based on a single effective diffusion coefficient for each system. Error analysis of the experimental and theoretical data indicated relatively large errors at low initial metal ion concentrations. Therefore the model was modified to introduce a surface coverage concentration dependent effective diffusivity to account for a contribution from surface diffusion.     

Cu(II) binding by dried biomass of red, green and brown macroalgae

Dried biomass of the marine macroalgae Fucus spiralis and Fucus vesiculosus (brown), Ulva spp. (comprising Ulva linza, Ulva compressa and Ulva intestinalis) and Ulva lactuca (green), Palmaria palmata and Polysiphonia lanosa (red) were studied in terms of their Cu(II) biosorption performance. This is the first study of its kind to compare Cu(II) uptake by these seaweeds in the South-East of Ireland. Potentiometric and conductimetric titrations revealed a variety of functionalities on the seaweed surface including carboxyl and amino groups, which are capable of metal binding. It was also found that, of the seaweeds investigated, F. vesiculosus contained the greatest number of acidic surface binding sites while Palmaria palmata contained the least. The metal uptake capacities of the seaweeds increased with increasing pH and kinetic behaviour followed a similar pattern for all seaweeds: a rapid initial sorption period followed by a longer equilibrium period. P. palmata reached equilibrium within 10min of exposure while F. vesiculosus required 60min. Correlation was found between the total number of acidic binding sites and the time taken to reach equilibrium. Fourier transform infra-red (FTIR) analysis of the seaweeds revealed the interaction of carboxyl, amino, sulphonate and hydroxyl groups on the seaweed surface with Cu(2+) ions while time course studies established the relative contribution of each of these groups in metal binding.     

Sorption and detoxification of chromium(VI) by aerobic granules functionalized with polyethylenimine

This study describes the modification of aerobic granules by grafting polyethylenimine (PEI) for simultaneous sorption and detoxification of Cr(VI). After modification, the uptake capacity of modified aerobic granules (MAG) showed about 401.5 mg/g at pH 5.5 and increased by 274% compared to the control. Adsorption experiments were carried out as a function of contact time, pH and concentration of Cr(VI). It was found that the equilibrium sorption can be attained within 3 h and the process obeys the Redlich-Peterson isotherm model. The adsorption process is a function of pH of the solution, with the greater adsorption at pH 5.2. The interaction characteristics between the Cr and MAG were elucidated by applying FTIR and XPS analyses. FTIR results showed that the -NH₂ groups in the sorbent are involved in the adsorption process. XPS results verified the presence of Cr(III) on the MAG surface in the pH range 1.5-8.5, suggesting that some Cr(VI) anions were reduced to Cr(III) during the sorption.     

Removal of Cu(II) and Cd(II) from aqueous solution by seafood processing waste sludge

Dried waste slurry generated in seafood processing factories has been shown to be an effective adsorbent for the removal of heavy metals from dilute solutions. Characterization of the sludge surface with scanning electron microscope and X-ray microanalyzer were carried out to evaluate the components on the sludge surface that are related to the adsorption of metal ions. Aluminum and calcium, as well as organic carbon are distributed on the surface of sludge. Alkalimetric titration was used to characterize the surface acidity of the sludge sample. The surface acidity constants, pKa1s and pKa2s, were 5.80 and 9.55, respectively. Batch as well as dynamic adsorption studies were conducted with 10(-5) to 5 x 10(-3) M Cu(II) and Cd(II). A surface complexation model with the diffuse layer model successfully predicted Cu(II) and Cd(II) removals in single metal solutions. Predictions of sorption in binary-adsorbate systems based on single-adsorbate data fits represented competitive sorption data reasonably well over a wide range of conditions. The breakthrough capacity found from column studies was different for each metal ion and the data reflect the order of metal affinity for the adsorbent material very well.     

Sorption of malachite green (a cationic dye) and heavy metals by dead biomass of Phormidesmis molle (cyanobacteria)‐dominated mat

The test mat biomass rapidly sorbed malachite green (MG; a cationic dye) and heavy metals from mono‐component, binary and ternary systems. In mono‐component system, the sorption of Cu, Cd and MG increased when pH was increased from 3 to 4. However, in binary and ternary systems sorption of metals and MG were not substantially influenced by pH within the range 3–5. The presence of Cu or MG in binary or ternary systems reduced the sorption of each other from the solution. However, Cd enhanced the sorption of MG from binary solution and vice versa. Moreover, the ability of mat biomass to rapidly sorb metal ions and malachite green from mono‐component, binary and ternary systems, together with easy harvesting of biomass due to self‐immobilized nature, make it a suitable sorbent for the treatment of wastewaters that concomitantly bear the both heavy metals and dyes as pollutants.     

Scavenging cadmium,copper, lead,nickel and zinc ions from aqueous solution by modified cellulosic sorbent

The adsorption of cadmium, copper, lead, nickel and zinc ions on maize Zea mays stalk meal was examined by equilibrium studies at 29°C. The amounts of the metal ions removed from solution depended on the metal ion type, the ionic size of the metals and were enhanced by EDTA (% N = 12.05) modification of the cellulosic sorbent. The sorption coefficient, K_d, of the metal ions between the adsorbent phase and the bulk aqueous phase was found. The sorption on the unmodified sorbent of lead ions from solutions containing zinc ions shows that lead ions are preferentially removed from solution.     

Cadmium(II) and zinc(II) adsorption by the aquatic moss Fontinalis antipyretica: effect of temperature, pH and water hardness

The biosorption of cadmium(II) and zinc(II) ions onto dried Fontinalis antipyretica, a widely spread aquatic moss, was studied under different values of temperature, initial pH and water hardness. The equilibrium was well described by Langmuir adsorption isotherms. Maximum biosorption capacity of cadmium was independent on temperature and averaged 28.0 mg g(-1) moss, whereas for zinc, capacity increased with temperature, from 11.5 mg g(-1) moss at 5 degrees C to 14.7 mg g(-1) moss at 30 degrees C. Optimum adsorption pH value was determined as 5.0 for both metal ions. Cadmium uptake was unaffected by the presence of calcium ions, but zinc sorption was improved when water hardness increased from 101.1 to 116.3 mg CaCO(3)l(-1). Inversely, as hardness increases, the competition with calcium ions strongly reduces the affinity of the biosorbent for zinc.     

Sorption of Zn(II), Pb(II), and Co(II) using natural sorbents: equilibrium and kinetic studies

Natural Jordanian sorbent (consisting of primary minerals, i.e., quartz and aluminosilicates and secondary minerals, i.e., calcite and dolomite) was shown to be effective for removing Zn(II), Pb(II) and Co(II) from aqueous solution. The major mineral constitutions of the sorbent are calcite and quartz. Dolomite was present as minor mineral and palygorskite was present as trace mineral. The sorbent has microporous structure with a modest surface area of 14.4 m(2)g(-1). pH(zpc) (pH of zero point charge) of the sorbent was estimated by alkaline-titration methods and a value of 9.5 was obtained. The sorption capacities of the metals were: 2.860, 0.320, 0.076 mmol cation g(-1) for Zn(II), Pb(II) and Co(II) at pH 6.5, 4.5 and 7.0, respectively. The shape of the experimental isotherm of Zn(II) was of a "L2" type, while that of Pb(II) and Co(II) was of a "L1" type according to Giles classification for isotherms. Sorption data of metals were described by Langmuir and Freundlich models over the entire concentration range. It was found that the mechanism of metal sorption was mainly due to precipitation of metal carbonate complexes. The overall sorption capacity decreased after acid treatment, as this decreased the extent of precipitation on calcite and dolomite. The effect of Zn(II) ions concentration on sorption kinetics was investigated. Kinetic data were accurately fitted to pseudo-first order and external diffusion models which indicated that sorption of Zn(II) occurred on the exterior surface of the sorbent and the contribution of internal diffusion mechanism was insignificant. Furthermore, the sorption rate of Zn(II) was found to be slow, where only 10-20% of the maximum capacity was utilized in the first 30 min of interaction.     

Sorption kinetics of Fe(II), Zn(II), Co(II), Ni(II), Cd(II), and Fe(II)/Me(II) onto hematite

The reactions of Fe(II) and other divalent metal ions including Zn, Co, Ni, and Cd on hematite were studied in single and competitive binary systems with high sorbate/sorbent ratios in 10 mM PIPES (pH 6.8) solution under strict anoxic conditions. Adsorbed Me(II) was defined as extractable by 0.5 N HCl within 20 h, and fixed Me(II) was defined as the additional amount that was extracted by 3.0 N HCl within 7 days. Binary systems contained Fe(II) plus a second metal ion. The extent of uptake of divalent metal ions by hematite was in order of Fe> or =Zn>Co> or =Ni>Cd. For all metals tested, there was an instantaneous adsorption followed by a relatively slow stage that continued for the next 1-5 days. This sequence occurred in both single and binary systems, and could have been due to a variety of sorption site types or due to slow conversion from outer- to inner-sphere surface complexes due to increasing surface charge. Sorption competition was observed between Fe(II) and the other metal ions. The displacement of Fe(II) by Me(II) was in order of Ni approximately Zn>Cd, and the displacement of Me(II) by Fe(II) was in order of Cd>Zn approximately Ni>Co. Fixed Fe(II) was in order of Fe+Co (20%)>Fe+Cd (6%)>Fe approximately Zn (4%)>Fe approximately Ni (4%) after 30 days. There was no fixation for the other metals in single or binary systems.     

The removal of nickel,copper and cadmium from aqueous solution using liver moss (Dumortiera hirsute Sw. nees)

The aim of this study was to investigate the use of liver moss (Dumortiera hirsute Sw. nees) as an alternative adsorbent for the removal of nickel, copper and cadmium from aqueous solution. The results showed that equilibrium contact time was 60?min and acidic pH was favourable for removal of metal ions. Higher initial metal ion concentrations led to lower removal. The data were fitted well both Langmuir and Freundlich isotherms. The monolayer adsorption capacities were 30.675, 35.971 and 53.476?mg/g for nickel, copper and cadmium, respectively. The presence of metal ions such as sodium, potassium and magnesium at concentration of 10?mM was found to have no significant effect on the removal of nickel, copper and cadmium. The removal of nickel, copper and cadmium was markedly inhibited, however, in the presence of calcium ion and heavy metal ions mixture in solutions. The kinetic data for removal processes were described by the pseudo-second-order model. The liver moss shows high potential as an economic and abundant material for the removal of metal ions from aqueous solution.     

The effects of strongly complexing ligands on the adsorptive partitioning of metal ions

This work investigated the effects of polyphosphate, a model ligand which forms strong complexes with metals, on metal sorption onto ferrihydrite. Adsorption experiments were conducted to study the partitioning of metal ions in systems containing a range of metal and ligand concentrations. The sorption of ligands, the associated sorption of charge and complexation of metals by ligands are important in controlling metal partitioning. In metal-free systems, the apparent maximum adsorption density is about 0.1 mol of polyphosphate per mol of Fe. The sorption of metals and/or metal-ligand complexes increases the maximum sorption density of ligands compared to systems where metal ions are not present. At total polyphosphate concentrations less than that needed to saturate the oxide surface, the presence of polyphosphate enhances the sorption of metals. When the concentration of polyphosphate exceeds that needed to saturate the oxide surface, the sorption of metals diminishes due to both the competition between dissolved and surface polyphosphate for metal ions and the dissolution of iron oxides.     

Removal of heavy metals from aqueous solution by nonliving Ulva seaweed as biosorbent

The growth of dense green seaweed mats of Ulva spp. is an increasing problem in estuaries and coasts worldwide. The enormous amount of Ulva biomass thus becomes a troublesome waste disposal problem. On the other hand, it has been revealed that nonliving seaweed biomass, particularly brown seaweeds, has a high capacity for assimilating heavy metals. In this study, the possibility of using Ulva seaweed biomass as a biosorbent for the removal of heavy metals was examined. After processing, the biomass material was very easy to separate from the aqueous solution using a mesh. The sorption capacity of Cd on Ulva biomass increased upon pretreatment with alkali solution. The outstanding function of the biosorbent was demonstrated at around pH 8. On the basis of the Langmuir isotherms of Cd, Zn and Cu using the alkali-pretreated biomass, the parameters q(m) and b were determined to be within the narrow range of 60-90 mg/g and 0.03-0.04 L/mg, respectively, for each metal. Given the q(m) and b values, Ulva seaweed is a good biosorbent material for removing heavy metals. In an experiment using artificial wastewater containing Cd, Zn, Cu, Cr and Ni, it was possible to remove each metal simultaneously using Ulva biomass. Adsorption by Ulva biomass is effective for the removal of heavy metals from wastewater.     

Myriophyllum alterniflorum DC., biomonitor of metal pollution and water quality. Sorption/accumulation capacities and photosynthetic pigments composition changes after copper and cadmium exposure

Watermilfoil genus Myriophyllum could be used in ecological surveys as in-situ biomonitors of metal pollution and water quality due to its ability to accumulate chemicals. The copper and cadmium sorption characteristics of Myriophyllum alterniflorum have been investigated. The Langmuir and Freundlich isotherms were used to model the metal sorption isotherms and the monolayer sorption capacities, as obtained by the Langmuir isotherm, were determined to be 13.9 mg/g and 11.1 mg/g for Cu2+ and Cd2+ respectively. Results have been compared with previous works on watermilfoils and are in accordance with those obtained on Myriophyllum spicatum. The sorption of the two metals was time-dependent and the kinetics fitted the pseudo-second-order equation well. The data were discussed in terms of ionic radii and HSAB concept. The phytotoxic effects assessed by classical (i.e. changes in biomass, node length) and photosynthetic pigments content endpoints have been investigated using chemometric techniques leading to an effect of cadmium onto photosynthetic pigments.     

碱激发水泥固化重金属和放射性金属分析

通过浸出毒性鉴别试验和长期浸出试验分析了碱激发水泥（AAC）对重金属和放射性金属的固化效果,并通过X射线衍射、红外光谱、扫描电镜-能谱等技术分析了重金属铜的加入对AAC产物微观结构的影响。AAC由水泥、硅灰、粉煤灰、磨细矿渣、偏高岭土和氢氧化钾制得。浸出毒性鉴别试验结果说明：所制备的AAC对重金属（铜、铅、镍、锌、镉）均具有较好的固化效果,固化效率在99.97％以上。加入的重金属铜进入到AAC产物中,影响到AAC产物中的O-Si-O键、Al-O-Si键和Si-O-Si键的周围环境,使其振动的频率发生变化,但没有引起AAC产物化学结构上的变化。长期浸出试验结果表明：AAC对放射性金属（锶、铯）的固化效果好于普通水泥,铯的浸出率显著高于同浸出龄期的锶的浸出率,说明铯比锶难以固定。研究表明：碱激发水泥对重金属和放射性金属有较好的固化效果,可以用来固化处理含有重金属和放射性金属的危险废物。