A comparative study on heavy metal biosorption characteristics of some algae

The biosorption of copper(II), nickel(II) and chromium(VI) from aqueous solutions on dried (Chlorella vulgaris, Scenedesmus obliquus and Synechocystis sp.) algae were tested under laboratory conditions as a function of pH, initial metal ion and biomass concentrations. Optimum adsorption pH values of copper(II), nickel(II) and chromium(VI) were determined as 5.0, 4.5 and 2.0. respectively, for all three algae. At the optimal conditions, metal ion uptake increased with initial metal ion concentration up to 250 mg l⁻¹. Experimental results also showed the influence of the alga concentration on the metal uptake for all the species. Both the Freundlich and Langmuir adsorption models were suitable for describing the short-term biosorption of copper(II), nickel(II) and chromium(VI) by all the algal species.     

Bioaccumulation of copper(II), lead(II) and chromium(VI) by growing Aspergillus niger

The effect of copper(II), lead(II) and chromium(VI) ions on the growth and bioaccumulation properties of Aspergillus niger was investigated as a function of initial pH and initial metal ion concentration. The optimum pH values for growth and metal ion accumulation were determined as 5.0, 4.5 and 3.5 for copper(II), lead(II) and chromium(VI) ions, respectively. Although all metal ion concentrations caused an inhibition effect on the growth of A. niger, it was capable of removing of copper(II) and lead(II) with a maximum specific uptake capacity of 15.6 and 34.4 mg g⁻¹ at 100 mg dm⁻³ initial copper(II) and lead(II) concentration, respectively. Growth of A. niger was highly effected by chromium(VI) ions and inhibited by 75 mg dm⁻³ initial chromium(VI) concentration since some inhibition occurred at lower concentrations.     

The use ofZoogloea ramigera in waste water treatment containing Cr(VI) and Cd(II) ions

Summary Optimum fermentation conditions forZ. ramigera were determined and various parameters which affected adsorption rates of chromium and cadmium ions onZ. ramigera were investigated. At 25°C the optimum adsorption pH of Cr(VI) and Cd(II) ions were 2.0 and 6.0 respectively. The adsorption rate of chromium and cadmium ion increased by increasing initial metal ion concentration up to 75 and 50 ppm respectively: at higher initial metal ion concentrations, the adsorption rates decreased.     

Study of the biosorption of different heavy metal ions onto Kraft lignin

The ability of Kraft lignin, a waste product of paper production, for removing copper, zinc, cadmium and chromium ions from water was investigated. The studies were conducted by a batch method to determine equilibrium parameters. The adsorbed heavy metal ions followed the order: Cr(VI) ? Cd(II) > Cu(II) > Zn(II). The influence of other ions such as Ni(II), Cd(II) and Pb(II), on Cu(II) adsorption by Kraft lignin was evaluated. Obtained results support the idea that adsorption behaviour of heavy metal ions have to be perceived from the aspect of possible influence of interfering ion species.     

Heavy metals removal by the microalga Scenedesmus incrassatulus in continuous cultures

The microalga Scenedesmus incrassatulus was grown under continuous regime in the presence of chromium(VI), cadmium(II) and copper(II), as single metal species and as mixtures of two or three metals, in a laboratory scale system. We used an artificial wastewater with low free ion activities (as determined by MINEQL+) due to the presence of EDTA (a strong chelating agent) but with total concentrations not suitable for acceptable environments. Chromium(VI) and cadmium(II) had positive interaction that increased the removal percentages of both these metals; we could not, however, detect any interaction with copper(II). S. incrassatulus was able to remove all the tested metals to some extent (25-78%), but bivalent metals were not removed as efficiently as reported in batch cultures, probably due to the high pH values there recorded. Chromium(VI) was more efficiently removed in continuous cultures than in batch culture, because the uptake of chromate could be favored by actively growing algae.     

Comparative studies on the adsorption of Cr(VI) ions on to various sorbents

The adsorption of Cr(VI) ions onto various sorbents (chitin, chitosan, ion exchangers; Purolite CT-275 (Purolite I), Purolite MN-500 (Purolite II) and Amberlite XAD-7) was investigated. Batch adsorption experiments were carried out as a function of pH, agitation period and concentration of Cr(VI) ions. The optimum pH for Cr(VI) adsorption was found as 3.0 for chitin and chitosan. The Cr(VI) uptake by ion exchangers was not very sensitive to changes in the pH of the adsorption medium. The maximum chromium sorption occurred at approximately 50 min for chitin, 40 min for Purolite II and 30 min for chitosan, Purolite I and Amberlite XAD-7. The suitability of the Freundlich and Langmuir adsorption models were also investigated for each chromium-sorbent system. Adsorption isothermal data could be accurately interpreted by the Langmuir equation for chitosan, chitin, Purolite I and Purolite II and by the Freundlich equation for chitosan, chitin and Amberlite XAD-7. The chromium(VI) ions could be removed from the sorbents rapidly by treatment with an aqueous EDTA solution and at the same time the sorbent regenerated and also could be used again to adsorb by heavy metal ions. The results showed that, chitosan, which is a readily available, economic sorbent, was found suitable for removing chromium from aqueous solution.     

Comparative study of Cd(II) and Cr(VI) biosorption on Staphylococcus xylosus and Pseudomonas sp. in single and binary mixtures

Biosorption of Cd(II) and Cr(VI) ions in single solutions using Staphylococcus xylosus and Pseudomonas sp., and their selectivity in binary mixtures was investigated. Langmuir and Freundlich models were applied to describe metal biosorption and the influence of pH, biomass concentration and contact time was determined. Maximum uptake capacity of cadmium was estimated to 250 and 278 mg g(-1), whereas that of chromium to 143 and 95 mg g(-1) for S. xylosus and Pseudomonas sp., respectively. In binary mixtures with Cd(II) ions as the dominant species, there is a profound selectivity for cadmium biosorption, reaching 96% and 89% for Pseudomonas sp. and S. xylosus, respectively, at 10 mg l(-1) Cd(II) and 5 mg l(-1) Cr(VI). Interesting, when chromium (VI) ions are the dominant species, there is selectivity towards chromium around 92% with S. xylosus only.     

Biosorption of Chromium,Copper, and Nickel Ions by Tamarindus Indica Fruit Nut Testa

Biosorption of chromium, copper, and nickel from aqueous solution by Tamarindus indica fruit nut testa (TFNT) in its pristine and acid-treated forms was studied under equilibrium and column-flow conditions. TFNT, a tannin-containing material, was characterized by energy dispersion x-ray fluorescence (EDXRF) and Fourier transform infrared (FTIR) spectral techniques and surface analysis. The effect of experimental variable parameters such as pH, concentration of metal ions, amount of adsorbent, and contact time on adsorption was investigated. Batch isothermal equilibrium data were analyzed on the basis of Langmuir and Freundlich adsorption isotherms. The kinetics of the adsorption process were studied in terms of Lagergren first-order kinetic model. The monolayer adsorption capacities of pristine and acid-treated forms of tamarind seed coat were found to be 44.8 and 77.5 mg/g for Cr(VI), 55.8 and 99.0 mg/g for Ni(II), and 84.7 and 85.4 mg/g for Cu(II) ions, respectively. The column-flow adsorption data were used to obtain breakthrough curves. The biosorbent loaded with the metal ions was regenerated using 1.0 M HCl and the regenerated bed was used for subsequent adsorption-desorption cycle.     

Removal of chromium from industrial waste by using eucalyptus bark

Several low cost biomaterials such as baggase, charred rice husk, activated charcoal and eucalyptus bark (EB) were tested for removal of chromium. All the experiments were carried out in batch process with laboratory prepared samples and wastewater obtained from metal finishing section of auto ancillary unit. The adsorbent, which had highest chromium(VI) removal was EB. Influences of chromium concentration, pH, contact time on removal of chromium from effluent was investigated. The adsorption data were fitted well by Freundlich isotherm. The kinetic data were analyzed by using a first order Lagergren kinetic. The Gibbs free energy was obtained for each system and was found to be -1.879 kJ mol(-1) for Cr(VI) and -3.885 kJ mol(-1) for Cr(III) for removal from industrial effluent. The negative value of deltaG0 indicates the feasibility and spontaneous nature of adsorption. The maximum removal of Cr(VI) was observed at pH 2. Adsorption capacity was found to be 45 mg/g of adsorbent, at Cr(VI) concentration in the effluent being 250 mg/l. A waste water sample containing Cr(VI), Cr(III), Mg, and Ca obtained from industrial unit showed satisfactory removal of chromium. The results indicate that eucalyptus bark can be used for the removal of chromium.     

Tolerance of a ruminant ciliate <Emphasis Type="Italic">Entodinium caudatum</Emphasis> against mercury,copper and chromium

The effects of three heavy metal cations, mercury (II), copper (II), and chromium (VI), on the growth of the rumen ciliate Entodinium caudatum in vitro culture was studied. The E. caudatum culture was challenged by HgCl₂, CuCl₂, and K₂Cr₂O₇ for a period of 4 days. The tested concentrations of mercury (II) and copper (II) were 1, 5, 10, 20, 50 mg/L and 2, 10, 20, 40 mg/L for chromium (VI) at single dose with either untreated or inhibited bacterial co-culture population. Effective metal concentrations required to reduce ciliate growth by 50% (EC₅₀) for mercury (II), copper (II), and chromium (VI) either with untreated or inhibited bacterial co-culture population after 24 h of metal application were 24, 20, and 21 or 15, 20, and 19 mg/L, respectively. After 4 days of metal application, corresponding EC₅₀ values for mercury (II), copper (II), and chromium (VI) were 16, 20, and 17 (with untreated bacterial population) or not determinable, 20, and 15 mg/L, respectively (with inhibited bacterial population). Increased sensitivity of E. caudatum to tested heavy metals with inhibited bacterial co-culture population indicate that the ciliate resistance to the heavy metal tested depends on detoxification abilities of rumen bacterial population.     

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.     

Biosorption of chromium(VI) from aqueous solution by cone biomass of Pinus sylvestris

Biosorption of chromium(VI) on to cone biomass of Pinus sylvestris was studied with variation in the parameters of pH, initial metal ion concentration and agitation speed. The biosorption of Cr(VI) was increased when pH of the solution was decreased from 7.0 to 1.0. The maximum chromium biosorption occurred at 150 rpm agitation. An increase in chromium/biomass ratio caused a decrease in the biosorption efficiency. The adsorption constants were found from the Freundlich isotherm at 25 degrees C. The cone biomass, which is a readily available biosorbent, was found suitable for removing chromium from aqueous solution.     

Removal characteristics of metal ions using degreased coffee beans: adsorption equilibrium of cadmium(II)

The feasibility of using coffee beans after being dripped and degreased (DCB) as an adsorbent for base metals such as copper(II), zinc(II), lead(II), iron(III) and cadmium(II) were examined. The compositions of the DCB were characterized by Fourier transform infrared spectroscopy, scanning electronic micrograph and fluorescent X-ray. It was found that DCB contain sulfur and calcium from the analysis using fluorescent X-ray. The plant cell wall in DCB has the porous structure from the scanning electron microscopy (SEM) analysis, and the specific surface area was determined to be 1.2 m2/g using the specific surface area analyzer. Batch adsorption experiments on DCB were carried out at various pHs in order to elucidate the selectivity of metal ions. All metals were adsorbed at low pH region (3.0-5.0). Of particular interest was the adsorption characteristics of cadmium(II) on DCB. The adsorption isotherm for cadmium(II) at pH 8 fitted with a Langmuir equation to yield an adsorption equilibrium constant of 55.2 mmol dm(-3) and an adsorption capacity of 5.98 x 10(-2) mmol g(-1). The desorption of cadmium(II) was easily achieved over 90% by a single batchwise treatment with an aqueous solution of hydrochloric acid or nitric acid at more than 0.01 mol dm(-3). These results suggested that DCB behaves as a cation exchanger.     

Biosorption of chromium(VI) by spent cyanobacterial biomass from a hydrogen fermentor using Box-Behnken model

The study explores utilization of waste cyanobacterial biomass of Nostoc linckia from a lab-scale hydrogen fermentor for the biosorption of Cr(VI) from aqueous solution. The biomass immobilized in alginate beads was used for removal of the metal in batch mode optimizing the process conditions adopting response surface methodology (RSM). Kinetic studies were done to get useful information on the rate of chromium adsorption onto the cyanobacterial biomass, which was found to follow pseudo second-order model. Four important process parameters including initial metal concentration (10-100 mg/L), pH (2-6), temperature (25-45 °C) and cyanobacterial dose (0.1-2.0 g) were optimized to obtain the best response of Cr(VI) removal using the statistical Box-Behnken design. The response surface data indicated maximum Cr(VI) biosorption at pH 2-4 with different initial concentrations of the metal in the aqueous solution. The biosorbent could remove 80-90% chromium from solutions with initial metal concentration of 10-55 mg/L. Involvement of the surface characteristics of the biomass was studied through its scanning electron micrographs and Fourier transform infrared (FTIR) analysis.     

Adsorption of heavy metal ions from aqueous solutions by activated carbon prepared from apricot stone

Apricot stones were carbonised and activated after treatment with sulphuric acid (1:1) at 200 degrees C for 24 h. The ability of the activated carbon to remove Ni(II), Co(II), Cd(II), Cu(II), Pb(II), Cr(III) and Cr(VI) ions from aqueous solutions by adsorption was investigated. Batch adsorption experiments were conducted to observe the effect of pH (1-6) on the activated carbon. The adsorptions of these metals were found to be dependent on solution pH. Highest adsorption occurred at 1-2 for Cr(VI) and 3-6 for the rest of the metal ions, respectively. Adsorption capacities for the metal ions were obtained in the descending order of Cr(VI) > Cd(II) > Co(II) > Cr(III) > Ni(II) > Cu(II) > Pb(II) for the activated carbon prepared from apricot stone (ASAC).     

Biosorption of hexavalent chromium from aqueous solution by a tropical basidiomycete BDT-14 (DSM 15396)

Summary A tropical white-rot basidiomycete, BDT-14 (DSM 15396) was investigated for its chromium (VI) biosorption potential from an aqueous solution. Pre-treatment of fungal biomass with acid resulted in 100% metal adsorption compared to only 26.64% adsorption without any pre-treatment. Chromium adsorption was a rapid process at early exposure resulting in 60% chromium removal within the first 2 h of exposure. An increase in biomass showed an increase in the total metal ions adsorption but a decrease in specific uptake of metal ions. The concentrations of chromium had a pronounced effect on the rate of adsorption. The adsorption efficiency was 100% when the initial Cr (VI) concentration was 100 mg l⁻¹ with 1,000 mg biomass. Only 47.5% adsorption was observed with 500 mg l⁻¹ Cr (VI) concentration. The adsorption data fit well with the Langmuir and Freundlich isotherm models. Comprehensive characterization of parameters indicates BDT−14 biomass as a promising material for Cr (VI) adsorption.     

The adsorption of copper(II) ions on to dehydrated wheat bran (DWB): determination of the equilibrium and thermodynamic parameters

The adsorption of copper(II) ions on to dehydrated wheat bran (DWB), a by-product of the flour process, was investigated as a function of initial pH, temperature, initial metal ion concentration and adsorbent dosage. The optimum adsorption conditions were initial pH 5.0, initial copper concentration 100 mg l⁻¹, temperature 60 °C and adsorbent dosage 0.1 g. The adsorption equilibrium was described well by the Langmuir isotherm model with maximum adsorption capacity of 51.5 mg g⁻¹ of copper(II) ions on DWB. The observation of an increase in adsorption with increasing temperature leads to the result that the adsorption of copper(II) ions on DWB is endothermic in nature. The thermodynamic parameters such as enthalpy, free energy and entropy changes were calculated and these values show that the copper(II)-DWB adsorption process was favoured at high temperatures.     

Patterns of tolerance to heavy metals among methane-utilizing bacteria

The susceptibility of obligate methane-utilizing bacteria, including 14 reference strains and 175 environmental isolates, to five readily available heavy metal pollutants was determined. The chloride salts of Hg(II), Cd(II), Cu(II), Cr(III) and Zn(II) were tested in a system free from organic matter. Methane-utilizers appeared to have relatively discrete metal tolerance patterns with resistances to all metals varying with isolation site. Methanotrophs proved to be quite sensitive to mercury and cadmium but relatively resistant to copper, chromium and zinc     

Biosurfactant Mediated Remediation Process Evaluation on a Mixture of Heavy Metal Spiked Topsoil Using Soil Column and Batch Washing Methods

This study investigated the effects of biosurfactant produced by a mangrove isolate on a heavy metal spiked soil remediation using two different methods of biosurfactant addition (pretreatment and direct application) at different concentrations (0.5%–5%) for 10 days employing column and batch method of washings. The FT-IR spectral and biochemical analysis confirmed the chemical nature of biosurfactant as a glycolipid. Pre-addition of biosurfactant at 0.5% concentrations and further incubation for a month resulted in better chromium removal than the direct biosurfactant washing method. A maximum recovery of lead (99.77%), nickel (98.23%), copper (99.62%), and cadmium (99.71%) were achieved with column washing method at 1% biosurfactant concentration. Release of 26% soluble fractions of nickel (pre-addition with biosurfactant) and 40% copper (direct application) were achieved by column washing method at 1.0% concentration of biosurfactant. A total of 0.034 mg/10 g of lead, 0.157 mg/10 g of nickel, 0.022 mg/10 g of copper, 0.025 mg/10 g of cadmium, and 0.538 mg/10 g of chromium were found to remain in the spiked soil after column washing with 1.0% biosurfactant solution. However, pre-addition of 0.5% biosurfactant treatment helps in maximum removal of chromium metal leaving a residual concentration of 0.426 mg/10 g of soil, suggesting effective removal at very low concentration. The average extraction concentration of metals in batch washings was between 93–100%, irrespective of the concentration of biosurfactant studied. In this study, the percentage removal of copper, cadmium, chromium, nickel, and lead from spiked soils by column washing was comparatively lower than batch washing.