Biosorptive removal of arsenic from drinking water

A biomass derived from the plant Momordica charantia has been found to be very efficient in arsenic(III) adsorption. An attempt was made to use this biomass for arsenic(III) removal under different conditions. The parameters optimized were contact time (5-150 min), pH (2-11), concentration of adsorbent (1-50 g/l), concentration of adsorbate (0.1-100mg/l), etc. It was observed that the pH had a strong effect on biosorption capacity. The optimum pH obtained for arsenic adsorption was 9. The influence of common ions such as Ca(2+), Mg(2+), Cd(2+), Se(4+), Cl(-), SO(4)(2-), and HCO(3)(-), at concentrations varying from 5 to 1000 mg/l was investigated. To establish the most appropriate correlation for the equilibrium curves, isotherm studies were performed for As(III) ion using Freundlich and Langmuir adsorption isotherms. The pattern of adsorption fitted well with both models. The biomass of M. charantia was found to be effective for the removal of As(III) with 88% sorption efficiency at a concentration of 0.5mg/l of As(III) solution, and thus uptake capacity is 0.88 mg As(III)/gm of biomass. It appears that this biomass should be used as a palliative food item. Further it also appears that the dietary habits may play a role in the toxic effects of ingested arsenic.     

Specific Treatment Technologies for Removing Arsenic from Water

Arsenic (As) is a highly toxic metalloid found in ground and surface water. Arsenic contamination in drinking water leads to harmful effects on human health. To eliminate arsenic from drinking water, several technologies such as coagulation, adsorption, ion exchange, filtration, membrane processes, etc., have been used. In this study, three technologies were evaluated for arsenic removal. Results from batch kinetic experiments showed that iron coated sand (IOCS‐2) can remove more than 90 % of As from synthetic water. Experiments were conducted with three different pH values (6, 7, and 8) and an initial As concentration of 260 μg/L. A new material, developed in this study, namely iron coated sponge (IOCSp), was found to have a high capacity in removing both As (V) and As (III). Each gram of IOCSp adsorbed about 160 μg of As within a 9‐hour contact period of IOCSp with As solution. Low pressure nanofiltration removed more than 94 % of As from an influent containing 440 μg/L As. The applied pressure was varied from 85 to 500 kPa.     

Toxicity and bioremediation of As(III) and As(V) in the green microalgae Botryococcus braunii: A laboratory study

Worldwide threats of fuel shortages in the near future and climate change because of greenhouse gas emissions are posing severe challenges and therefore it is vital to search for sustainable ways of preventing the consequences. The dual use of microalgae for phycoremediation and biomass production for sustainable biofuel production is a viable choice. Phycoremediation of As(III) and As(V) ions using microalgae was investigated in a two-staged batch reactor. Accumulation and toxicity of inorganic arsenic forms (As(III) and As(V)) to green microalgae Botryococcus braunii depend on environmental factors. Dissolved oxygen and pH cycles did not significantly differ due to the absence or presence of arsenic (either As(III) or As(V)) ions in the culture. Monod model was utilized for representing the growth kinetics of microalgae in pure media containing various concentrations of nitrate ions. Maximum specific growth rate and saturation constant were found to be 0.14788 d^?1 and 0.00105 g/L, respectively. With the increase in concentration of phosphate in growth medium, the growth of microalgae increased. Media with NaCl (1.0 g/L) and NaHCO₃ (1 g/L) resulted in higher maximum biomass concentration. Effect of coexisting ions on phycoremediation of As(III) and As(V) ions using microalgae was studied.     

Fixed-bed biosorption of Cu2+ by polyacrylonitrile-immobilized dead cells of Saccharomyces cerevisiae

Dead cells of Saccharomyces cerevisiae 54 were immobilized by entrappment in polyacrylonitrile. The beads obtained were used to adsorb copper in an up-flow fixed-bed column. The effect of polymer content and cell loading were studied to optimize the porosity and the efficiency in copper removal of the biosorbent beads in a batch system. The optimal concentration of the polyacrylonitrile was assumed to be 12%(w/v) and a concentration of 0.5 g cell dry weight in 1 g polymer was most effective in adsorption of Cu²⁺. The adsorption capacity of this biosorbent was 27 mg Cu²⁺/g dry biomass at 200 mg/l initial concentration of copper ions. Adsorption of Cu²⁺ in a batch system was studied using different initial concentrations of the solute. The optimal conditions in the up-flow column of the following parameters were determined: flow rate, bed height, and initial concentration of Cu²⁺ of the solutions. Results of fixed-bed biosorption showed that breakthrough and saturation time appeared to increase with the bed height, but decrease with the flow rate and the initial concentration. The linearized form of the Thomas equation was used to describe dynamic adsorption of metal ions. As a result, the adsorption capacity of the batch system and the column system was compared. Desorption of copper ions was achieved by washing the column biomass with 0.1 M HCl at an eluent flow rate of 1 ml/min. The reusability of the immobilized biomass was tested in five consecutive adsorption-desorption cycles. The regenerated beads retained over 45% of their original adsorption capacity after five A/D cycles. This revised version was published online in August 2006 with corrections to the Cover Date.     

Removal of thallium from aqueous solutions by modified Aspergillus niger biomass

The present study involves an investigation of various treated fungal biomasses of Aspergillus niger for the removal of thallium from aqueous solutions. Batch pH and kinetic studies were carried out to examine the effects of pH and contact time on the adsorption process. Among various pH values studied, the optimum pH was found to be between 4 and 5. The equilibrium time for Tl adsorption was found to be 6h and the rate of Tl adsorption was rapid in the initial hours. Both Lagergren's pseudo first-order model and Ho's pseudo second-order model well described the reaction kinetics. Batch adsorption experiments conducted at room temperature (22+/-1 degrees C) showed that the adsorption pattern followed the Freundlich isotherm model. Column studies using iron oxide-coated immobilized fungal biomass showed lower adsorption capacities compared to batch studies.     

Application of Freundlich and Langmuir models to multistage purification process to remove heavy metal ions by using Schizomeris leibleinii

The adsorption of iron(III), lead(II) and cadmium(II) ions onto Schizomeris leibleinii, a green alga, was studied with respect to initial pH, temperature, initial metal ion and biomass concentration to determine the optimum adsorption conditions. Optimum initial pH for iron(III), lead(II) and cadmium(II) ions were 2.5, 4.5 and 5.0 at optimum temperature 30°C, respectively. The initial adsorption rates increased with increasing initial iron(III), lead(II) and cadmium(II) ion concentrations up to 100, 100 and 150 mg l⁻¹, respectively. The Freundlich and Langmuir adsorption isotherms were developed at various initial pH and temperature values. The adsorption of these metal ions to S. leibleinii was investigated in a two-stage mixed batch reactor. The residual metal ion concentrations (C_eq) at equilibrium at each stage for a given ‘quantity of dried algae (X₀)/volume of solution containing heavy metal ion (V₀)’ ratio were calculated using Freundlich and Langmuir isotherm constants. The experimental biosorption equilibrium data for iron(III), lead(II) and cadmium(II) ions were in good agreement with those calculated by both Freundlich and Langmuir models. The adsorbed iron(III), lead(II) and cadmium(II) ion concentrations increased with increasing X₀/V₀ ratios while the adsorbed metal quantities per unit mass of dried algae decreased.     

The characteristics of Escherichia coli adsorption of arsenic(III) from aqueous solution

The potential of using Escherichia coli (E. coli) as adsorbent for the adsorption of As(III) from aqueous solution was assessed. Various parameters like pH, initial concentration and temperature have been investigated. It is found that the adsorption of As(III) is pH dependent and the optimum value was 2.0. Kinetics studies revealed that the equilibrium of the adsorption of As(III) on to E. coli was obtained within 30 min and the process was followed with the pseudo-2nd-order kinetic model. The equilibrium adsorption data obtained at different temperatures were fitted better with Langmuir than Freundich isotherm. The adsorption capacity of E. coli for As(III) is increased with the increasing of temperature and the maximum adsorption capacity is 1.111 mg/g which obtained at 40°C. Potentiometric titration and Fourier transform infra-red spectroscopy were applied to reveal the mechanisms of the As(III) binding. Amino, amide, amine group and C–H of the alkane are determined to be involved in As(III) binding based on the results.     

The role of denitrification on arsenite oxidation and arsenic mobility in an anoxic sediment column model with activated alumina

Arsenite (As(III)) is the predominant arsenic (As) species in reducing environments. As(III) is less strongly adsorbed than As(V) at circumneutral pH conditions by common non‐iron metal oxides in sediments such as those of aluminum. Therefore, oxidation of As(III) to As(V) could contribute to an improved immobilization of As and thus help mitigate As contamination in groundwater. Microbial oxidation of As(III) is known to readily under aerobic conditions, however, the dissolved oxygen (O₂) concentration in groundwater may be limited due to the poor solubility of O₂ and its high chemical reactivity with reduced compounds. Nitrate (${\rm NO}_{3}^{{-} } $ ), can be considered as an alternative electron acceptor, which can support oxidation of As(III) to As(V) by denitrifying bacteria. In this study, two up‐flow sediment columns packed with activated alumina (AA) were utilized to demonstrate the role of denitrification on the oxidation of As(III) to As(V) and its contribution to improved As adsorption onto AA. One column was supplied with ${\rm NO}_{3}^{{-} } $ (C1) and its performance was compared with a control column lacking ${\rm NO}_{3}^{{-} } $ (C2). During most of the operation when the pH was in the circumneutral range (days 50–250), the release of arsenic was greater from C2 compared to C1. The effluent As concentrations started increasing on days 60 and 100 in C2 and C1, respectively. Complete breakthrough started on day 200 in C2; whereas in C1, complete breakthrough was never achieved. The effluent and solid phase As speciation was dominated by As(V) in C1, indicating the occurrence of As(III) oxidation due to ${\rm NO}_{3}^{{-} } $ ; whereas in C2, only As(III) was dominant. This study illustrates a bioremediation or natural attenuation process based on anoxic microbial ${\rm NO}_{3}^{{-} } $ ‐dependent oxidation of As(III) to more readily adsorbed As(V) as a means to enhance the immobilization of As on alumina oxide particles in subsurface environments. Biotechnol. Bioeng. 2010;107: 786–794. © 2010 Wiley Periodicals, Inc.     

Supplemental sodium phytate and microbial phytase influence iron availability in growing rats.

Five groups of individually housed albino rats (n = 7 each, initial average weight = 42 g) were fed diets based on corn starch and casein over a 4-week period. All diets were supplemented with 35 mg/kg of iron from FeSO4 x 7 H2O. Group I (control) was fed the basal diet free of phytic acid (PA) and phytase. By replacing corn starch by 7.5 g (groups II and IV) and 15 g phytic acid (groups III and V) from sodium phytate per kg diet, molar PA/iron ratios of 18 and 36 were obtained. In groups IV and V, 1000 U phytase from Aspergillus niger per kg diet were added. Food conversion efficiency ratio and growth rate as well as iron in plasma and spleen, hemoglobin, red blood cell count and erythrocyte zinc protoporphyrin were not influenced by the different dietary treatments. Dietary phytate reduced apparent iron absorption in groups II and III. Furthermore hematocrit, transferrin saturation and iron concentration in liver and femur were lowered in rats fed diets with PA, while total and latent iron-binding capacity of plasma increased. Microbial phytase supplementation (groups IV and V) partly counteracted the antinutritive effects of phytic acid on iron availability.     

Arsenic removal from the aqueous system using plant biomass: a bioremedial approach

Metal species released into the environment by technological activities tend to persist indefinitely, circulating and eventually accumulating throughout the food chain, thus becoming a serious threat to the environment. Environment pollution by toxic metals occurs globally through military, industrial, and agricultural processes and waste disposal. Bioremediation processes are the target of recent research and are considered low-cost, ecofriendly methods to alleviate the current problems of water decontamination, particularly for remote and rural areas. The present piece of work reports the unexploited sorption properties of the powdered seed of the plant Moringa oleifera (SMOS) for the removal of Arsenic [As(III) and As(V)] from aqueous solutions. Sorption studies, using standard practices, result in the standardization of optimum conditions such as biomass dosages (2.0 g), metal concentrations (25 ppm), contact time (60 min) and volume of the test solutions (200 ml) at pH 7.5, for As(III) and pH 2.5 for As(V). Maximum sorption for As(III) and As(V) species is 60.21 and 85.6%, respectively. Protein/Amino acid-Arsenic interactions are found to play an important role in the biosorption process using plant biomass SMOS.     

The removal of As(III) and As(V) from aqueous solutions by waste materials

The use of different waste materials such as Atlantic Cod fish scale, chicken fat, coconut fibre and charcoal in removing arsenic [As(III) and As(V)] from aqueous solutions was investigated. Initial experimental runs, conducted for both As(III) and As(V) with the aforementioned materials, demonstrated the potential of using Atlantic Cod fish scale in removing both species of arsenic from aqueous streams. Therefore, the biosorbent fish scale was selected for further investigations and various parameters such as residence time, adsorbent dose, initial concentration of adsorbate, grain size of the adsorbent and pH of the bulk phase were studied to establish optimum conditions. The maximum adsorption capacity was observed at pH value 4.0. The equilibrium adsorption data were interpreted by using both Freundlich and Langmuir models. Rapid small-scale column tests (RSSCT) were also performed to determine the breakthrough characteristics of the arsenic species with respect to packed biosorbent columns.     

Enhanced Adsorption of Trivalent Arsenic from Water by Functionalized Diatom Silica Shells

The potential of porous diatom silica shells as a naturally abundant low-cost sorbent for the removal of arsenic in aqueous solutions was investigated in a batch study. The objective of this work was to chemically modify the silica shells of a diatom Melosira sp. with bifunctional (thiol and amino) groups to effectively remove arsenic in its toxic As(III) form (arsenite) predominant in the aquatic environment. Sorption experiments with this novel sorbent were conducted under varying conditions of pH, time, dosage, and As(III) concentration. A maximum adsorption capacity of 10.99 mg g^-1 was achieved within 26 h for a solution containing 12 mg L^-1 As(III) at pH 4 and sorbent dosage of 2 g L^-1. The functionalized diatom silica shells had a surface morphological change which was accompanied by increased pore size at the expense of reduced specific surface area and total pore volume. As(III) adsorption was best fitted with the Langmuir-Freundlich model, and the adsorption kinetic data using pore surface diffusion model showed that both the external (film) and internal (intraparticle) diffusion can be rate-determining for As(III) adsorption. Fourier transform infrared spectroscopy (FTIR) indicated that the thiol and amino groups potentially responsible for As(III) adsorption were grafted on the surface of diatom silica shells. X-ray photoelectron spectroscopy (XPS) further verified that this unique sorbent proceeded via a chemisorption mechanism through the exchange between oxygen-containing groups of neutral As(III) and thiol groups, and through the surface complexation between As(III) and protonated nitrogen and hydroxyl groups. Results indicate that this functionalized bioadsorbent with a high As(III) adsorption capacity holds promise for the treatment of As(III) containing wastewater.     

用固定化弗劳地柠檬酸杆菌XP05从溶液中回收铂

比较了5种固定弗劳地柠檬酸杆菌XP05菌体的方法,其中明胶海藻酸钠包埋法为固定菌体的最佳方法。扫描电子显微镜观察表明,XP05菌体较均匀地分布于包埋基质中。固定化XP05菌体吸附Pt^4＋受吸附时间、固定化菌体浓度、溶液的pH值和Pt^4＋起始浓度的影响。吸附作用是一个快速的过程;吸附Pt^4＋的最适pH值为1.5;在50～250 mg P^4＋/L范围内,吸附量与Pt^4＋起始浓度成线性关系,吸附过程符合Langmuir和Freundlich吸附等温模型。在Pt^4＋起始浓度250 mg/L、固定化菌体2.0 g/L、pH 1.5和30℃条件下,振荡吸附60 min, 吸附量为35.3 mg/g。0.5 mol/L HCl能使吸附在固定化菌体上的Pt解吸98.7%。从废铂催化剂处理液回收铂的结果表明,在Pt^4＋起始浓度111.8 mg/L、固定化菌体4.0 g/L、pH 1.5和30℃条件下,振荡吸附60 min, 吸附量为20.9 mg/g。在填充床反应器中,在Pt^4＋起始浓度50 mg/L、流速1.2 ml/min、固定化菌体1.86 g的条件下,饱和吸附量达24.7 mg/g; 固定化XP05菌体经4次吸附解吸循环后吸附率仍达78％。     

Adsorption of Cr(VI) and As(V) ions by modified magnetic chitosan chelating resin

Cross-linked magnetic chitosan anthranilic acid glutaraldehyde Schiff's base (CAGS) was prepared for adsorption of both As(V) and Cr(VI) ions and their determination by ICP-OES. Prepared cross-linked magnetic CAGS was investigated by means of SEM, FTIR, wide angle X-ray diffraction (WAXRD) and TGA analysis. The adsorption properties of cross-linked magnetic CAGS resin toward both As(V) and Cr(VI) were evaluated. Various factors affecting the uptake behavior such as pH, temperature, contact time, initial concentration of metal ions, effect of other ions and desorption were studied. The equilibrium was achieved after about 110 min and 120 min for As(V) and Cr(VI), respectively at pH = 2. The adsorption kinetics followed the mechanism of the pseudo-second order equation for all systems studied, evidencing chemical sorption as the rate-limiting step of adsorption mechanism and not involving a mass transfer in solution. The equilibrium data were analyzed using the Langmuir, Freundlich, and Tempkin isotherm models. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 58.48 and 62.42 mg/g for both Cr(VI) and As(V), respectively. Cross-linked magnetic CAGS displayed higher adsorption capacity for Cr(VI). The adsorption capacity of the metal ions increased with increasing temperature under optimum conditions in case of Cr(VI), but decreased in case of As(V). The metal ion-loaded cross-linked magnetic CAGS were regenerated with an efficiency of greater than 88% using 0.2 M sodium hydroxide (NaOH).     

Synthesis and characterization of iron(llI) chelating analogues of siderophores on organic solid supports

A series of iron(III)-selective chelating resins have been modeled after the structural features of the naturally occurring siderophore compounds with hydroxamate, catecholate and salicylate iron binding groups. Amberlite IRC-50 was derivatized via an acid chloride intermediate to produce poly(hydroxamic acid) (IRC-50 PHA/N-H and IRC-50 PHA/N- CH₃), poly(catecholate) (IRC-50 PEDA 2,3-DHBAD and IRC-50 PEDA 3,4-DHBA) and poly(salicylate) (IRC-50 PEDA 2-HBAD) chelating resins with enhanced iron(III) binding capacity. The poly(hydroxamic acid) IRC-50 PHA/N-CH₃ was produced in 57% yield, the highest conversion yet reported for such derivatizations. This is the first report of a catechol or salicylate derivatization of Amberlite IRC-50. The highest overall iron(III) binding capacities yet reported for poly(hydroxamic acid) modifications of commercially available polymer supports were obtained for IRC-50 PHA/N-H (1.75 mmol Fe/g dry resin) and IRC-50 PHA/N-CH₃ (1.52 mmol Fe/g dry resin). IRC-50 PHA/N-H was also found to be an effective iron chelator when tested at ambient environmental conditions. Selectivity for iron- (III) was also determined by measuring Fe³⁺ binding capacity in the presence of Ca²⁺. UVVis spectroscopy with photoacoustic detection was used to assign the coordination environment of iron(III) in these chelating resins as bis-(FeL₂) and tris-(FeL₃) chelates. As an alternative synthetic approach, a poly(amidoxime) (PAO) chelating resin was synthesized by polymerization of appropriate monomers. Comparison between the two synthetic approaches showed that PAO bound a greater amount of iron(III) at flow-through column conditions, while IRC-50 PHA/N-H exhibited a greater iron(III) binding capacity at batch equilibration conditions.     

Removal of heavy metals from stainless steel effluents by waste biomass from Brazilian alcoholic beverage production

The capacity of waste biomasses from sugar-cane aguardente, a traditional Brazilian spirit, for metal biosorption was assessed. Free biomass and biomass immobilized onto chitin and Dowex (ion-exchange resin) were utilized to remove chromium, iron and nickel from both synthetic solutions and stainless steel effluents. The best performance in terms of metal sorbed was observed in with free biomass, with the following adsorption capacity: 70% chromium, 50% iron and 20% nickel at pH 4.0.     

Removal of selenium and arsenic by animal biopolymers

The animal biopolymers prepared from hen eggshell membrane and broiler chicken feathers, which are byproducts of the poultry-processing industry, were evaluated for the removal of the oxyanions selenium [Se(IV) and Se(VI)] and arsenic [As(III) and As(V)] from aqueous solutions. The biopolymers were found to be effective at removing Se(VI) from solution. Optimal Se(IV) and Se(VI) removal was achieved at pH 2.5–3.5. At an initial Se concentration of 100 mg/L (1.3 m M), the eggshell membrane removed approx 90% Se(VI) from the solution. Arsenic was removed less effectively than Se, but the chemical modification of biopolymer carboxyl groups dramatically enhanced the As(V) sorption capacity. Se(VI) and As(V) sorption isotherms were developed at optimal conditions and sorption equilibrium data fitted the Langmuir isotherm model. The maximum uptakes by the Langmuir model were about 37.0 mg/g and 20.7 mg/g of Se(VI) and 24.2 mg/g and 21.7 mg/g of As(V) for eggshell membrane and chicken feathers, respectively.     

Cadmium adsorption by non-living biomass of the semi-macroscopic brown alga,Ectocarpus siliculosus,grown in axenic mass culture and localisation of the adsorbed Cd by transmission electron microscopy

Non-living, freeze-dried material of the brown algaEctocarpus siliculosus (Phaeophyceae) demonstrated high equilibrium uptake of Cd from aqueous solutions (Fehrmann & Pohl, 1993). The alga was grown in 250-L photobioreactors under various growth conditions (light, salinity and nutrient concentrations) in order to obtain larger quantities of biomass and to improve its Cd adsorption capacity. To derive further knowledge on the biosorbant phenomenon different adsorption parameters such as pH for the sorption process and kinetics of Cd adsorption were tested. The maximum adsorption capacity of the freeze-dried biomass exceeded 41 mg Cd per g biomass. After repeated addition of low Cd concentrations the maximum adsorption capacity was lower (31.4 mg Cd per g biomass). In comparison with other adsorbing materials (activated carbon, silica gel, siliceous earth)E. siliculosus showed significantly higher adsorption capacity. Desorption of deposited Cd with 0.1 M HCl resulted in no changes of the adsorption capacity through five subsequent adsorption-/desorption-cycles. Hence, driedE. siliculosus appears to be an efficient material for the elimination of Cd from industrial waste water.Transmission electron microscopic investigations showed an electron dense area in the outer surface layers of the cell wall after Cd adsorption indicating the most likely location of Cd fixation.Author for correspondence     

Arsenic removal from the aqueous system using plant biomass: a bioremedial approach

Metal species released into the environment by technological activities tend to persist indefinitely, circulating and eventually accumulating throughout the food chain, thus becoming a serious threat to the environment. Environment pollution by toxic metals occurs globally through military, industrial, and agricultural processes and waste disposal. Bioremediation processes are the target of recent research and are considered low-cost, ecofriendly methods to alleviate the current problems of water decontamination, particularly for remote and rural areas. The present piece of work reports the unexploited sorption properties of the powdered seed of the plant Moringa oleifera (SMOS) for the removal of Arsenic [As(III) and As(V)] from aqueous solutions. Sorption studies, using standard practices, result in the standardization of optimum conditions such as biomass dosages (2.0 g), metal concentrations (25 ppm), contact time (60 min) and volume of the test solutions (200 ml) at pH 7.5, for As(III) and pH 2.5 for As(V). Maximum sorption for As(III) and As(V) species is 60.21 and 85.6%, respectively. Protein/Amino acid–Arsenic interactions are found to play an important role in the biosorption process using plant biomass SMOS.