Synthetic Metal Solutions Research Articles

A molecular extraction process for vanadium based on tandem selective complexation and precipitation

Recycling vanadium from alternative sources is essential due to its expanding demand, depletion in natural sources, and environmental issues with terrestrial mining. Here, we present a complexation-precipitation method to selectively recover pentavalent vanadium ions, V(V), from complex metal ion mixtures, using an acid-stable metal binding agent, the cyclic imidedioxime, naphthalimidedioxime (H2CIDIII). H2CIDIII showed high extraction capacity and fast binding towards V(V) with crystal structures showing a 1:1 M:L dimer, [V2(O)3(C12H6N3O2)2]2−, 1, and 1:2 M:L non-oxido, [V(C12H6N3O2)2] ̶ complex, 2. Complexation selectivity studies showed only 1 and 2 were anionic, allowing facile separation of the V(V) complexes by pH-controlled precipitation, removing the need for solid support. The tandem complexation-precipitation technique achieved high recovery selectivity for V(V) with a selectivity coefficient above 3 × 105 from synthetic mixed metal solutions and real oil sand tailings. Zebrafish toxicity assay confirmed the non-toxicity of 1 and 2, highlighting H2CIDIII’s potential for practical and large-scale V(V) recovery.

Photothermal air gap membrane distillation for the removal of heavy metal ions from wastewater

As the world population grows, pure water becomes increasingly scarce, making wastewater treatment necessary. However, the processes currently used to treat industrial wastewater are generally energy-intensive, highlighting the need to develop environmentally friendly wastewater treatment technologies. To address this issue, a photothermal air–gap membrane distillation system was developed and tested for the first time to remove heavy metal ions from wastewater. Activated carbon particles at different concentrations were used in the prepared polyvinylidene fluoride membranes as components for solar energy recovery. Zinc, one of the most common heavy metals in industrial wastewater in the United Arab Emirates, was used as a model contaminant in this study. The results showed that the use of Activated Carbon particles to modify Polyvinylidene fluoride membranes can significantly improve solar absorption (97%) and porosity (60.6%), resulting in a permeate flux of 0.32 L/m2h and a rejection of 97% of Zn ions. Additionally, the optimized membrane was tested using a synthetic heavy metal solution and showed high rejection rates for most of the tested heavy metals (Zn2+, Fe3+, Cu2+, Cr3+, and Ni2+), which can be potentially used in the industrial heavy metal removal process. The developed photothermal water treatment system can provide a highly efficient and scalable water treatment process.

Thermodynamic and kinetic models for the removal of copper and cadmium using industrial effluents by mixed adsorbent

The potential of Activated Charcoal and bone Charcoal as a low cost material for the removal of copper and cadmium from synthetic metal solution was studied. A number of experiments were performed in order to determine the potential capacity of the adsorbent in terms of thermo Dynamic equilibrium from the batch data. The Positive values of change in Enthalpy show that the process is endothermic in nature for Cd (II) and the negative values of Change in Enthalpy shows that the process is exothermic in nature for Cu (II). The standard Gibb’s free energy values are positive which means that the process is not spontaneous in nature. The negative values of ΔS show that there is decrease in randomness at the solid/solution interface during the adsorption of copper. The study revealed that mixed adsorbent prepared by blending the activated charcoal and bone charcoal in 1: 1 ratio has more potential to act as an adsorbent for the removal of Cu and Cd from aqueous solution. The optimum temperature was found to be 40°C for both the metals. The higher correlation coefficient R2(0.9824) value shown that cadmium ions were well fitted the thermodynamic model comparing copper ions. The batch adsorption studies have been carried out for 2 hrs considering all the 6 parameters by optimizing each of them. The data obtained for optimized parameters were studied through fitting of kinetic models such as Pseudo-first order and Pseudo second order models for both Copper and Cadmium along with Correlation or regression coefficient (R2) values.

Kinetic Studies of Heavy Metal Removal from Industrial Wastewater by Using Natural Zeolite

The present work involves the study of the removal of Cu2+, Fe3+, Pb2+ and Zn2+ from synthetic metal solutions using natural zeolite. Laboratory experiments were used to investigate the efficiency of adsorbents in the uptake of heavy metals from industrial wastewater. The kinetic study was used to identify the effect of parameters that affect the rate of adsorption and evaluated their impact on the efficiency of the zeolite in the removal of heavy metals from industrial wastewater. Natural zeolite (clinoptilolite) as adsorbent contacted with multi-component synthetic solutions containing Cu2+, Fe3+, Pb2+ and Zn2+ ions without any pre-modifications and every hour 15 ml of the samples were filtered and taken for metal ion concentration analysis using the ICP-OES. The pH values were monitored and adjusted regularly. The results showed that the capacity of the adsorbents for the removal of heavy metals increased with a greater mass of absorbent, increased initial solution pH, increased agitation speed and higher solution concentration.

Removing heavy metals from landfill leachate using electrospun polyelectrolyte fiber mat-laminated ultrafiltration membrane

This study investigated the removal of selected heavy metals from landfill leachate by electrospun polyacrylic acid (PAA)/polyallylamine hydrochloride (PAH)-laminated ultrafiltration (UF) membranes (PAA/PAH-UF). The effect of leachate matrix on metal removal by the PAA/PAH-UF membrane was also examined. In synthetic metal solutions, the PAA/PAH-UF membrane exhibited 38–85% higher removal efficiency when compared to the unmodified membrane. This could be attributed to complexation of the metal ions with the carboxylate ions (–COO-) from the PAA/PAH fiber mats. Heavy metal removal was generally higher (up to approximately 18%) in landfill leachates than the laboratory-prepared solutions, likely resulting from the fouling of PAA/PAH fiber mat and the UF membrane substrate and the metal-organic complexation. The higher metal ion removal efficiencies (up to 20%) by the PAA/PAH-UF membranes in the presence of Suwannee River natural organic matter (SRNOM) were associated with the higher concentrations (50 and 100 mg/L) of SRNOM. When compared to the lower concentration (10 mg/L), metal removal increased (up to 30%) at higher concentrations (50 and 100 mg/L), with the influence of SRNOM being the most pronounced for Cu, followed by Cd and Pb. The enhanced metal removal, in the presence of SRNOM, can be attributed to metal complexation with SRNOM functional groups in addition to the rich functional groups from the PAA/PAH fiber mats. The trivial difference in flux decline of the PAA/PAH-UF membrane compared to the unmodified membrane may be outweighed by the marked enhancement in heavy metal removal when functionalizing the membrane with PAA/PAH fiber mats.

Removal of toxic metals using a novel PHA resin-fixed bed column performance study

The performance and efficiency of a fixed bed column loaded with a three-dimensionally crosslinked polyhydroxamic acid resin is studied with glass column. Experiments were carried out with synthetic metal solutions containing Cu(II), Sr(II), Gd(III) individually and with mixed solution containing Cu(II), Sr(II), Gd(III) and U(VI) to establish the efficiency of the fixed bed resin for a mixed solution. The “S” shaped break through curve was generated and percentage saturation of the bed was estimated. The percentage saturation at 10% breakthrough volume was found to be 68.3% for Cu(II) and Sr(II) 71.3% and 65.6% for Gd(III).

Separation of Cu (II) Ions by Hydroxamic Acid Functionalized Poly (Methyl Methacrylate) Grafted Cellophane Membranes

Hydroxamic acid functionalized Poly (methyl methacrylate) grafted cellophane ions exchanger membranes have been used for Cu (II) ions separation from synthetic metal solutions. Factors affecting the adsorption process namely copper ions concentration, adsorption time, adsorption temperature, and grafting percentage have been studied. It was found that the Cu+2 uptakes increase by increasing the grafting percentage. The maximum uptake amount of Cu+2 ions obtained with membranes of grafting percentage 58%. However, the recovery of the adsorbed Cu+2 ions has not been affected by variation of the grafting percentage. Equilibrium has been obtained after 60 minutes of adsorption while the temperature was found of neglectable effect. Fourier transforms infrared analysis and thermal gravimetric analysis provided evidences of the adsorption processes. Moreover, the kinetics and isotherms of the adsorption process have been monitored. The membranes show a very good applicability and reusability where very slow reduction of the adsorption and regeneration processes has been detected after ten cycles.

Removal of heavy metals from water using electrospun polyelectrolyte complex fiber mats

This study investigated the removal of heavy metals from water using electrospun polyelectrolyte (PE) complex fibers of polyacrylic acid (PAA) and polyallylamine hydrochloride (PAH). PE fiber mats were fabricated under various electrospinning operating conditions to optimize fiber size and stability in aqueous solution. The stable fiber mats were evaluated for their efficiency in removing heavy metals in synthetic metal solutions. The effect of water matrix on heavy metal removal using the PAA/PAH fiber mats was probed by comparing metal removals in the presence and absence of natural organic matter (NOM). The fiber mats exhibited approximately 63 %, 42 %, and 21 % removals of lead (Pb), cadmium (Cd), and copper (Cu), respectively in synthetic metal solutions at pH 3.4. Furthermore, approximately 70 %, 98 %, and 92 % removals of Pb, Cd, and Cu, respectively were observed at a higher pH (7.4). The heavy metal removal by the PAA/PAH complex fiber mats may be attributed to the association of the metal ions with carboxylate ions from the fibers. The presence of NOM in the metal-spiked solutions resulted in higher removal of metals by the fiber mats. This can be attributed to the availability of NOM-derived carboxylic acid groups, which resulted in increased metal-carboxylate complexations. This study implies that water matrix plays an important role that must be evaluated when removing metals using PE complex fibers.

The use of natural zeolite to remove heavy metals Cu (II), Pb (II) and Cd (II), from industrial wastewater

In this study, the adsorption behavior of Cu2+, Pb2+ and Cd2+ from synthetic metal solutions using natural zeolites was studied in order to investigate the efficiency of adsorbents of heavy metals ...

Induction of non-protein thiols and phytochelatins by cadmium in Eichhornia crassipes

Impact of root Cd concentration on production of cysteine, non-protein thiols (NP-SH), glutathione (GSH), reduced glutathione (GSSG), and phytochelatins (PCs) in Eichhornia crassipes exposed to different dilutions of brass and electroplating industry effluent (25%, 50%, and 75%), and synthetic metal solutions of Cd alone (1, 2.5, and 3.5 ppm) and with Cr (1 ppm Cd + 1 ppm Cr, 2.5 ppm Cd + 3 ppm Cr, and 3.5 ppm Cd + 4 ppm Cr) was assessed in a 45 days study. Different treatments were used to understand and compare differential antioxidant defense response of plant under practical drainage (effluent) and experimental synthetic solutions. The production of NP-SH and cysteine was maximum under 2.5 ppm Cd + 3 ppm Cr treatments i.e., 1.78 µmol/g fw and 288 nmol/g fw, respectively. The content of GSH declined whereas that of GSSG increased progressively with exposure duration in all treatments. HPLC chromatograms revealed that the concentrations of PC2, PC3, and PC4 (248, 250, and 288 nmol-SH equiv.g−1 fw, respectively) were maximum under 1 ppm Cd, 1 ppm Cd + 1 ppm Cr, and 2.5 ppm Cd + 3 ppm Cr treatments, respectively. PC2, PC3, and PC4 concentrations increased with Cd accumulation in the range 812–1354 µg/g dry wt, 1354–2032 µg/g dry wt and 2032–3200 µg/g dry wt, respectively. Thus, the study establishes a direct proportionality relationship between concentration/length of phytochelatins and root Cd concentrations, upto threshold limits, in E. crassipes.

Elucidation of preferential elimination of Cr(VI) via bioinspired adsorbents: a comparative assessment

The present study investigates uptake of Cr(VI) from synthetic metal solution by superheated steam-activated biochar (SABC) made from roots of Colocasia esculenta and synthetic zeolite (ZRHA) prepared from rice husk ash under the influence of pH (1–7), adsorbent dose (1–100 mg/L), initial Cr(VI) concentration (5–190 mg/L), temperature (15–55 °C), agitation speed (100–170 rpm) for a contact time of 30–1440 min. ZRHA and SABC were able to remove metal ions from a stock solution of 90 and 110 mg/L of Cr(VI) with a removal of 85.89% and 94.8%, respectively. Metal ion adsorption onto zeolite ZRHA followed monolayer adsorption, whereas biochar SABC employed multilayer adsorption. Kinetic studies suggested that adsorption of Cr(VI) ions could follow both physisorption and chemisorption depending on the adsorbent used. The two-compartment dynamic model study revealed Cr(VI) adhesion followed a slow phase of adsorption which suggested intraparticle diffusion to be a prominent rate-limiting factor for both cases. The thermodynamic study claimed that Cr(VI) adsorption was a temperature dependent phenomenon. Instrumental studies by TEM, SEM, EDX and FT-IR also advocated their part on Cr(VI) removal. Also, crystallinity of both the adsorbents was determined from their XRD analysis. Thus, the current study promotes both ZRHA and SABC to be a promising adsorbent for Cr(VI) removal from contaminated aqueous solution.

DETERMINATION OF ADSORPTION KINETICS OF COCONUT HUSK ADSORBENT FOR HEAVY METALS REMOVAL USING LANGMUIR AND FREUNDLICH ISOTHERM EXPRESSIONS

Adsorption of heavy metal cationic ions (Cr, Pb, and Cu) onto coconut husk carbon (CHC) adsorbent has been studied using batch-adsorption method. The study was carried out to investigate the adsorption kinetic and adsorption isotherm of the coconut husk adsorbent for the removal of heavy metals in waste liquid effluent. The influence of pH, contact time, adsorbent dose, and adsorbent concentration, and temperature on the adsorption process was also studied. Results indicated an initial increase in adsorption rate, and optimal removal of heavy metal was reached within 70 minutes, further increase in contact time and temperature show significant change in equilibrium concentration. Also, further increase in adsorbent dosage revealed significant change in the sorption capacity of the CHC. The adsorption isotherms could be fitted well by both Langmuir and Freundlich models. The RI (equilibrium parameter) value in the present investigation was less than 1 (one) which indicates that the adsorption of the heavy metals ions on the CHC is favorable. The value of n for this study which indicates the degree of non-linearity between solution concentration and adsorption were 0.31–0.39, this result indicated that the adsorption of heavy metals onto the CHC is a chemical sorption. After treatment of synthetic heavy metal solution with the CHC, the adsorption isotherm model analysis revealed that the adsorption capacity (b) of CHC for the heavy metal were 89 mg/L (Cr), 125.5 mg/L (Pb), and 129.7 mg/L (Cu). Conclusively, the results indicate that the freely abundant agricultural waste-coconut husk can be treated for heavy metal adsorption but it’s not economically viable because it’s not renewable due to the chemisorption nature of the adsorption process.

Biosorption of Cr(III) from aqueous solution using an agricultural by-product jute stick powder: Equilibrium and kinetic studies

The adsorption capacity of chromium(III) from synthetic waste water solution by a low cost biomaterial, Jute Stick Powder (JSP)was examined. A series of batch experiments were conducted at different pH values, adsorbent dosage and initial chromium concentration to investigate the effects of these experimental conditions. To analyze the metal adsorption on to the JSP, most common adsorption isotherm models were applied. To study the reaction rate, the kinetic and diffusion models were also applied. The morphological structure and variation of functional groups in the JSP before and after adsorption was examined by scanning electron microscope (SEM) and Fourier transform infrared spectrometry (FT-IR). Maximum chromium removal capacities of JSP was 84.34%with corresponding equilibrium uptake 8.4 mg/g from 50 mg/L of synthetic metal solution in 60 minutes of contact time at pH = 6.0 and 28 °C with continuous stirring at 180 rpm. The percent sorption of the biomass decreased with increasing concentration of metal ion but increased with decreasing pH, increasing contact time and adsorbent doses. Data for this study indicated a good correspondence with both isotherms of Langmuir and Freundlich isotherm. The analysis of kinetic indicated that Chromium was consistent with the second-order kinetic adsorption model. The rate of removal of Cr(III) ions from aqueous solution by JSP was found rapid initially within 5-30 minutes and reached in equilibrium in about 40 minutes. The investigation revealed that JSP, a low cost agricultural byproduct, was a potential adsorbent for removal of heavy metal ions from aqueous solution.

Robust superhydrophobic electrospun membrane fabricated by combination of electrospinning and electrospraying techniques for air gap membrane distillation

Membrane pore wetting is the main problem hindering long term stability of permeate flux quality in membrane distillation (MD) applications. A superhydrophobic membrane with micro and nanostructured surface features can offer a unique solution to resolve this issue. Thus, a modified electrospun membrane was fabricated using a combination of electrospinning and electrospraying. The membrane surface hydrophobicity was enhanced by constructing a beaded structure from spraying a mixture of non-fluorinated alumina (Al2O3) nanoparticles (NPs) mixed with low concentration of PVDF polymer on an electrospun base membrane made from PVDF. The results revealed that a rough surface with a hierarchical structure can be constructed, which could not only enhance the membrane hydrophobicity, but also further enhance the permeate efficiency by improving parameters such as flux and rejection. Additionally, the membrane hydrophobicity could be further tuned by controlling the bead spinning volume. Our study shows that the modified membrane with 7.8 μm beads layer thickness has boosted the liquid entry pressure (LEP) by 61% from 15.5 psi and the water contact angle to 154°. The performance of modified membranes with different spraying volume (1–5 ml) along with the neat electrospun and commercial membranes were examined in an air gap membrane distillation (AGMD) application for 5 h using a 2.5 wt% of synthetic heavy metal solution as a wastewater model. Then, the optimized superhydrophobic membrane with 2 ml spinning volume (ES15–2) was further tested in comparison with the commercial membrane during long-term operations (30 h) using 3.5 wt% of mixed heavy metals. The flux was 18.67 LMH (l m−2 h−1) for modified membrane (ES15–2) compare with 12.62 LMH for commercial PVDF membrane during 30 h of long-term operation with feed and coolant temperature at 60 °C, 20 °C, respectively. The present superhydrophobic membrane fabricated by a combined electrospinning/electrospray method shows high potential for MD applications.

Screening and selection of indigenous metal tolerant fungal isolates for heavy metal removal

Abstract Heavy metal removal efficiency of indigenously present metal tolerant fungal isolates obtained from a scrap dumpsite was assessed in this study. Four fungal isolates were selected based on their ability to grow in multi-metal supplemented media. Minimum inhibition concentrations of these four isolates were determined against individual metals; lead (II) (50–400 mgL−1), cadmium (II) (50–400 mgL−1), arsenic (III) (10–100 mgL−1) and mercury (II) (10–100 mgL−1). Their ability to remove metals from synthetic aqueous medium was tested and the heavy metal–fungi combination which showed the highest removal efficiency was selected. Live biomass of the selected isolate dispensed in lead solution with concentrations of 50 mgL−1, 100 mgL−1 and 150 mgL−1 showed a removal of 92.27%, 92.73% and 89.36% respectively at the end of the 40th h. Scanning Electron Microscopy with Electron Dispersive X-ray (SEM-EDX) of the treated biomass confirmed the biosorptive ability of the isolate for lead when compared with the control biomass. Fourier Transforms Infra-red (FTIR) Spectroscopy showed the probable involvement of amide, carboxylic acid, hydroxyl and isocyanate groups in the adsorption of lead from the synthetic metal solution.

Equilibrium and kinetic studies on biosorption potential of charophyte biomass to remove heavy metals from synthetic metal solution and municipal wastewater

ABSTRACTThe risk of heavy metal contamination in domestic water causes serious health and environmental problems. Biosorption has been considered as an efficient and alternative way for treatment of heavy metal–contaminated wastewater. The potentials of dried charophytes, Chara aculeolata and Nitella opaca, to biosorb lead (Pb), cadmium (Cd), and zinc (Zn) from synthetic solutions and municipal wastewater were investigated. The efficiency of metal removal was studied under varied conditions in different sorbent dosages, pH, and contact times. Biosorption isotherm and kinetics were used to clarify heavy metal preference and biosorption mechanism. C. aculeolata and N. opaca performed well in the biosorption of all three metal ions, with preference towards Pb, followed by Cd and Zn, in the single-metal solutions. Pb adsorption onto algal biomass followed first-order rate kinetics (N. opaca) and intraparticle diffusion (C. aculeolata and N. opaca). These results indicated physical adsorption process between Pb ions and both algal biomasses. Cd and Zn biosorption kinetics fitted the second-order rate model, indicating chemical adsorption between metal ions and both algae. The experimental data of three-metal biosorption fitted well to Langmuir isotherm model, suggesting that the metal ion adsorption occurred in a monolayer pattern on a homogeneous surface. C. aculeolata exhibited slightly higher maximum uptake of Pb, Cd, and Zn (105.3 mgPb/g, 23.0 mgCd/g, 15.2 mgZn/g) than did N. opaca (104.2 mgPb/g, 20.5 mgCd/g, 13.4 mgZn/g). In multi-metal solutions, antagonistic effect by metal competition was observed. The ability of charophytes to remove Pb and Zn was high in real municipal water (81–100%). Thus, the charophytic biomass may be considered for the treatment of metal contamination in municipal wastewater.

Sewage sludge as barrier material for heavy metals in waste landfill

Abstract Heavy metal pollutants in the leachate of waste landfill are a potential threat to the environment. In this study, the feasibility of using municipal sewage sludge as barrier material for the containment of heavy metal pollutants from solid waste landfills was evaluated by compaction test and hydraulic conductivity test concerning compaction property, impermeability and heavy metal retardation. Results of the compaction test showed that the maximum dry density of 0.79 g·cm−3 was achieved at the optimum water content of about 60%. The hydraulic conductivities of compacted sewage sludge permeated with synthetic heavy metal solutions were in the range of 1.3×10−8 – 6.2×10−9 cm·s−1, less than 1.0 ×10−7cm·s−1 recommended by regulations for barrier materials. Chemical analyses on the effluent from the hydraulic conductivity tests indicated that the two target heavy metals, Zn and Cd in the permeants were all retarded by compacted sewage sludge, which might be attributed to the precipitation and adsorption of heavy metal ions. The results of this study suggest that specially prepared material from sewage sludge could be used as a barrier for waste landfills for its low permeability and strong retardation to heavy metal pollutants.

Thermodynamic and Hydro Dynamic Modeling Studies Using Mixed Adsorbent Prepared from Activated Charcoal and Bone Charcoal for the Removal of Copper and Cadmium

and bone Charcoal as a low cost material for the removal of copper and cadmium from synthetic metal solution was studied. A number of experiments were performed in order to determine the potential capacity of the adsorbent in terms of thermo Dynamic equilibrium from the batch data and Hydro dynamic study from the column data equilibrium experiments. The Positive values of change in Enthalpy show that the process is endothermic in nature for Cd (II) and the negative values of Change in Enthalpy shows that the process is exothermic in nature for Cu (II). The standard Gibb’s free energy values are positive which means that the process is not spontaneous in nature. The negative values of ΔS show that there is decrease in randomness at the solid/solution interface during the adsorption of copper. The basic hydrodynamic parameters of the packed bed are analyzed. The influence of different parameters such as liquid velocity, particles size and void age on mass transfer in packed beds is represented. The data for mass transfer in the investigated system are shown using Sherwood number (Sh), Schmidt number (Sc), mass transfer coefficient (K) and Colburn factor (JD) as a function of Reynolds number (Re) for particles and for column. The plot between Reynolds number (Re) and the ratio of Sh/ Sc are represented at different flow rates. Therefore in the present investigation it was summarized that large flow rates and smaller bed heights rendered the minimum possible resistance for the transfer of metal ions from liquid phase to packed bed. The study revealed that mixed adsorbent prepared by blending the activated charcoal and bone charcoal in 1: 1 ratio has more potential to act as an adsorbent for the removal of Cu and Cd from aqueous solution.

Selective recovery of Pd(II) from extremely acidic solution using ion-imprinted chitosan fiber: Adsorption performance and mechanisms

A novel, selective and acid-resisting chitosan fiber adsorbent was prepared by the ion-imprinting technique using Pd(II) and epichlorohydrin as the template and two-step crosslinking agent, respectively. The resulting ion-imprinted chitosan fibers (IIF) were used to selectively adsorb Pd(II) under extremely acidic synthetic metal solutions. The adsorption and selectivity performances of IIF including kinetics, isotherms, pH effects, and regeneration were investigated. Pd(II) rapidly adsorbed on the IIF within 100min, achieving the adsorption equilibrium. The isotherm results showed that the maximum Pd(II) uptake on the IIF was maintained as 324.6–326.4mgg−1 in solutions containing single and multiple metals, whereas the Pd(II) uptake on non-imprinted fibers (NIF) decreased from 313.7 to 235.3mgg−1 in solution containing multiple metals. Higher selectivity coefficients values were obtained from the adsorption on the IIF, indicating a better Pd(II) selectivity. The amine group, supposedly the predominant adsorption site for Pd(II), was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The pH value played a significant role on the mechanism of the selective adsorption in the extremely acidic conditions. Furthermore, the stabilized performance for three cycles of sorption/desorption shows a potential for further large-scale applications.

Enzyme-based glucose delivery: a possible tool for biosorbent preparation for heavy metal removal from polluted environments

This study was performed to examine the influence of the controlled glucose supply technology, EnBase(®) Flo, on growth and heavy metals uptake capacity of two Bacillus strains isolated from food industry wastewater. Bacillus sp. growth on EnBase Flo (mineral salt complex medium containing starch-derived polymer as substrate) was examined in 24 deep well plates, controlling the glucose amount release by adding two amyloglucosidase concentrations (3 and 6 UL(-1)). Adsorption of the heavy metals Zn(2+), Cd(2+) and Pb(2+) was assessed in a single component system using synthetic metal solutions and as a function of the initial concentration of adsorbate, equilibrium time and removal efficiency. The Langmuir and Freundlich adsorption models were used for the mathematical description of the biosorption equilibrium and isotherm constants. A pseudo second-order model was applied to describe the uptake rate for two isolates. The EnBase(®) Flo technology improved the cells growth over ten times after 24 h of fed-batch cultivation. The EnBase(®) Flo technology improved the Cd(2+) and Pb(2+) uptake capacity of the bacterial strains by approximately 55 and 44 %, respectively. The biosorption of each metal was fairly rapid (within 30 min), which could be an advantage for large scale treatment of contaminated sites. This initial study may be a basis for future developments to apply EnBase Flo for the biomass production used further as biosorbent for heavy metal removal from aqueous solutions.