Heavy metals biosorption from aqueous solution by simple eucaryotic organisms

Biosorption of cadmium and chromium (III) ions by means of selected yeast species has been estimated. Kinetics and equilibrium measurements have shown the reliable efficiency of both metals removal for Candida tropicalis. The influence of pH and ionic strength on biosorption process has been examined as well. For both metals the adsorption isotherms have been presented. The equilibrium of chromium (III) sorption has appeared compatible to Langmiur model and the maximum sorption capacity has been determined.     

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.     

The treatment of chromium tanning wastewater using natural marl

Abstract

The technical feasibility of removing chromium(III) from contaminated tannery wastewater by adsorption on naturally available marl, referred to as HEWAR in Palestine, has been investigated by batch experiments. The effects of various parameters on the percentage relative adsorption concentration were carried out by UV-vis spectrophotometry. Percentage relative concentration curves showed an increase with time until approaching a plateau (adsorption capacity). The adsorption capacity increased with the marl-to-liquid ratio, providing complete removal of chromium above 0.003g mL^?1 accomplished within 7 hours, while the marl particles were kept in suspension by stirring. The adsorption capacity increased with pH above 5.0, and decreased below this value. One sample of marl can be used for adsorbing chromium from various batches of wastewater until the adsorption sites are full.     

Biosorption of chromium (Cr(III)/Cr(VI)) on the residual microalga Nannochloris oculata after lipid extraction for biodiesel production

In order to increase the economic feasibility of biodiesel production from microalgae, the residual biomass after biodiesel production can be utilized as biosorbent for heavy metal removal. In this study, biosorption of chromium by residual Nannochloris oculata after lipid extraction was investigated. Increased surface area of N. oculata was observed after lipid extraction. Cr(III) removal increased as the pH increased from 2 to 6, while Cr(VI) removal was highest at pH 2 and it decreased with the increase in pH. Cr(VI) was reduced to Cr(III) in the presence of biomass under acidic conditions; X-ray photoelectron spectroscopy revealed that the converted Cr(III) was bound to the biomass. Chromium removal was significantly enhanced at high chromium concentrations, which indicates that surface reactions may occur at high chromium/biomass ratios. FTIR study indicated that phosphate and carboxyl functional groups of the biomass were mainly responsible for chromium binding.     

Short-term batch studies on biological removal of chromium from synthetic wastewater using activated sludge biomass

Biological treatment of Cr(VI)-containing wastewater has drawn much attention recently as a method to treat environmental Cr(VI) contamination. The activated sludge method, due to its convenient operation and easy-to-scale-up, has been widely applied to treat municipal wastewater and some industrial wastewaters. In order to develop a suitable technique using activated sludge as the biomass to continuously remove Cr(VI) from wastewater, this paper investigated in short-term batch experiments the environmental elements affecting chromium biological removal from synthetic wastewater. The dissolved oxygen (DO), Cr(VI) initial concentration, biomass density, temperature, glucose content in the influent and contact time were observed to strongly influence chromium removal. It was found that the chromium removal efficiency decreased with the increase of DO and Cr(VI) initial concentration as well as glucose content in the feed, but increases in temperature and contact time improved the chromium removal efficiency. Although raising biomass concentration resulted in an increased chromium removal efficiency under both anaerobic and aerobic conditions, its influence on specific chromium removal was not significant.     

Heavy metals (Cd, Pb, Zn, Ni, Cu and Cr(III)) removal from water in Malaysia: post treatment by high quality limestone

This paper presents the results of research on heavy metals removal from water by filtration using low cost coarse media which could be used as an alternative approach to remove heavy metals from water or selected wastewater. A series of batch studies were conducted using different particle media (particle size 2.36-4.75 mm) shaken with different heavy metal solutions at various pH values to see the removal behaviour for each metal. Each solution of cadmium (Cd), lead (Pb), zinc (Zn), nickel (Ni), copper (Cu) and chromium (Cr(III)) with a concentration of 2 mg/L was shaken with the media. At a final pH of 8.5, limestone has significantly removed more than 90% of most metals followed by 80% and 65% removals using crushed bricks and gravel, respectively. The removal by aeration and settlement methods without solid media was less than 30%. Results indicated that the removal of heavy metals was influenced by the media and not directly by the pH. Investigations on the removal behaviour of these metals indicated that rough solid media with the presence of carbonate were beneficial for the removal process. Adsorption and precipitation as metals oxide and probably as metals carbonate were among the two mechanisms that contributed to the removal of metals from solution.     

Chromium removal from a real tanning effluent by autochthonous and allochthonous fungi

Heavy metals represent an important ecological and health hazard due to their toxic effects and their accumulation throughout the food chain. Conventional techniques commonly applied to recover chromium from tanning wastewaters have several disadvantages whereas biosorption has good metal removal performance from large volume of effluents. To date most studies about chromium biosorption have been performed on simulated effluents bypassing the problems due to organic or inorganic ligands present in real industrial wastewaters that may sequestrate the Cr(III) ions. In the present study a tanning effluent was characterized from a mycological point of view and different fungal biomasses were tested for the removal of Cr(III) from the same tanning effluent in which, after the conventional treatments, Cr(III) amount was very low but not enough to guarantee the good quality of the receptor water river. The experiments gave rise to promising results with a percentage of removed Cr(III) up to 40%. Moreover, to elucidate the mechanisms involved in biosorption process, the same biomasses were tested for Cr(III) removal from synthetic aqueous solutions at different Cr(III) concentrations.     

Hexavalent chromium removal from aqueous solutions by a novel powder prepared from Colocasia esculenta leaves

In this study, batch removal of hexavalent chromium from aqueous solutions by powdered Colocasia esculenta leaves was investigated. Batch experiments were conducted to study the effects of adsorption of Cr(VI) at different pH values, initial concentrations, agitation speeds, temperatures, and contact times. The biosorbent was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectrometer analysis. The biosorptive capacity of the adsorbent was dependent on the pH of the chromium solution in which maximum removal was observed at pH 2. The adsorption equilibrium data were evaluated for various adsorption isotherm models, kinetic models, and thermodynamics. The equilibrium data fitted well with Freundlich and Halsey models. The adsorption capacity calculated was 47.62 mg/g at pH 2. The adsorption kinetic data were best described by pseudo-second-order kinetic model. Thus, Colocasia esculenta leaves can be considered as one of the efficient and cheap biosorbents for hexavalent chromium removal from aqueous solutions.     

Characteristics of molybdate-impregnated chitosan beads (MICB) in terms of arsenic removal from water and the application of a MICB-packed column to remove arsenic from wastewater

The removal of arsenic (As) species, such as As(III) and As(V), from water by molybdate-impregnated chitosan beads (MICB) in both batch and continuous operations was studied. The effects of pH, temperature, coexisting ions, and arsenic concentrations were studied in batch tests. Studies on the kinetic adsorption of MICB, the recovery of arsenic by the desorption solution, and the reuse of MICB were also carried out. The practicality and efficiency of an MCIB-packed column on arsenic removal were evaluated in a continuous system on industrial arsenic-containing wastewater discharged during the manufacture of GaAs supports. The results indicate that MICB favor the adsorption of both As(V) and As(III). The optimal pH value for As(III) and As(V) removal was 5. The adsorption of arsenic on the MICB is most likely an exothermic reaction. The effect of coexisting ions was varied and depended on their concentrations and species. The optimal desorption solution for arsenic recovery was 1M H2SO4, which resulted in a 95% efficiency for As(III) and 99% for As(V). In the continuous tests, the MICB-packed column exhibited excellent arsenic removal from wastewater without any pretreatment. These results provide strong evidence of the potential of MICB for removing As from industrial wastewaters.     

Isolation of a novel chromium(III) binding protein from bovine liver tissue after chromium(VI) exposure

In the ongoing investigation into the biological importance and toxicity issues surrounding the bioinorganic chemistry of chromium, the accepted literature procedure for the isolation of the biological form of chromium, low molecular weight chromium binding protein (LMWCr) or chromodulin, was investigated for its specificity. When chromium(VI) is added to bovine liver homogenate, results presented here indicate at least four chromium(III) binding peptides and proteins are produced and that the process is non-specific for the isolation of LMWCr. A novel trivalent chromium containing protein (1) has been isolated to purity and initial characterization is reported here. Chromium(III) identification was determined by optical spectroscopy and diphenylcarbazide testing. This chromium binding protein has a molecular weight of 15.6kDa, which was determined from both gel-electrophoresis and mass spectrometry. The protein is comprised primarily of Asx, Glx, His, Gly/Thr, Ala, and Lys in a 1.00:2.51:0.37:2.09:0.39:1.17 ratio and is anionic at pH 7.4. In addition, the protein binds approximately 2.5 chromium(III) ions per molecule.     

Adsorption of chromium(III) on lignin

In order to assess the possibility of using lignin to remove Cr(III) from waters, the adsorption of Cr(III) on lignin isolated from black liquor, a waste product of the paper industry, was investigated. The influences of pH, lignin dosage, contact time, ionic strength, Cr(III) concentration and other metals were investigated. The Cr(III) adsorption was strongly dependent on pH and adsorbent dosage, but independent of ionic strength and other metal ions. The adsorption kinetic data can be described well with pseudo-second-order model and the equilibrium data can be well fitted using Langmuir two-surface model with a maximum adsorption capacity of 17.97 mg/g. Cr(III) adsorption on lignin was mainly through the ion-exchange mechanism and formed inner-sphere complexes with lignin. Successful application in removing Cr(III) was achieved by using a real wastewater sample. This study indicates that lignin has the potential to become an effective and economical adsorbent for the removal of Cr(III) from wastewaters.     

Removal of hexavalent chromium by fungal biomass of <Emphasis Type="Italic">Mucor racemosus</Emphasis>: influencing factors and removal mechanism

This study reported the hexavalent chromium removal by untreated Mucor racemosus biomass and the possible mechanism of Cr (VI) removal to the biomass. The optimum pH, biomass dose, initial Cr (VI) concentration and contact time were investigated thoroughly to optimize the removal condition. The metal removal by the biomass was strongly affected by pH and the optimum pH ranged from 0.5 to 1.0. The residual total Cr was determined. It was found that dichromate reduction occurred at a low very low pH value. At biomass dose 6 g/l, almost all the Cr (VI) ions were removed in the optimum condition. Higher removal percentage was observed at lower initial concentrations of Cr (VI) ions, while the removal capacity of the biomass linearly depended on the initial Cr (VI) concentration. More than half of Cr (VI) ions were diminished within 1 h of contact and removal process reached a relative equilibrium in approximately 8 h. Almost all of the Cr (VI) ions were removed in 24 h when initial concentrations were below 100 mg/l. The equilibrium data were fitted in to the Langmuir and the Freundlich isotherm models and the correlated coefficients were gained from the models. A Fourier transform infrared spectra was employed to elucidate clearly the possible biosorption mechanism as well.     

Biological removal of carcinogenic chromium(VI) using mixed Pseudomonas strains

The contamination of soil and wastewaters with Cr(VI) is a major problem. It has been suggested that microbial methods for Cr(VI) reduction are better than chemical methods, as they do not add other ions or toxic chemicals to the environment. In this study an aerobic reduction of Cr(VI) to Cr(III) by employing mixed Pseudomonas cultures isolated from a marshy land has been reported. The role of chromium concentration, temperature, pH and additives on the microbial reduction of Cr(VI) has been investigated. NADH was found to enhance the rate of reduction of Cr(VI). Complete reduction of chromium(VI) has been possible even at chromium(VI) concentrations of 300 ppm. Ions like SO(4)(2-) and poly-phenols inhibited the metabolic activity relating to Cr(VI) reduction. Under optimal conditions 100 mg/L of Cr(VI) was completely reduced within 180 min.     

Speciation and Environmental Fate of Chromium in Rivers Contaminated with Tannery Effluents

Redox and size speciation of chromium in rivers contaminated with tannery wastewater was carried out to provide insight into its transport and removal mechanisms. Total chromium was determined with Inductively Coupled Plasma‐Mass Spectrometry and Cr (VI) with Catalytic Adsorption Stripping Voltammetry. For the size speciation, particles were retained with a cartridge filter (cut‐off 1.2 μm) and the total filterable fraction was further fractionated with Tangential Flow Filtration to determine the concentrations of chromium associated with the High Molecular Weight Colloidal (HMWC), Low Molecular Weight Colloidal (LMWC) and Truly Dissolved (TD) fractions. Two fluvial systems of similar sizes, but located in contrasting climatic zones, were selected for comparison: the Sebou‐Fez system in Morocco and Dunajec River‐Czorsztyn Reservoir system in Poland. Particulate Cr dominated in the Sebou‐Fez system (about 90 %); while in the Dunajec‐Czorsztyn system, it represented only 17–53 % of the total chromium in raw water. Still, the partition coefficients [K_d] were of the same magnitude. Chromium (III) was the only form detected in Sebou‐Fez, whereas in Dunajec‐Czorsztyn Cr (VI) was also present with its proportion increasing downstream from the input of tannery wastewater due to the preferential removal of Cr (III). In the filtered water in Morocco a large fraction of Cr occurred in the HMWC fraction (50–70 %) at the two most contaminated sites, while the LMWC and TD forms prevailed at the non‐contaminated sites in the Sebou River. At a very high concentration, in the water in the proximity of tanneries (well above the theoretical saturation level) Cr precipitated as polynuclear Cr‐hydroxide. In Dunajec‐Czorsztyn, the partition of Cr (III) was approximately equal between the HMWC, LMWC and TD fractions, in contrast to Cr (VI) which occurred almost exclusively in the TD fraction. In both systems, Cr (III) was rapidly removed from the water to the sediments. The confluence of the Sebou with the Fez and the Czorsztyn reservoir trapped efficiently Cr (III) preventing its spreading over long distances. Cr (VI) showed conservative behavior and bypassed the Czorsztyn Reservoir. This study provides a first set of data on the partitioning of Cr (III) and Cr (VI) between the particulate, the colloidal and truly dissolved fractions in fluvial systems contaminated with tannery effluents. It also suggests that, in these systems, truly dissolved Cr (III) can be adequately modeled from the total filterable concentrations.     

Highly enhanced adsorption for decontamination of lead ions from battery wastewaters using chitosan functionalized with xanthate

Decontamination of lead ions from aqueous media has been investigated using cross linked xanthated chitosan (CMC) as an adsorbent. Various physico-chemical parameters such as contact time, amount of adsorbent, concentration of adsorbate were optimized to simulate the best conditions which can be used to decontaminate lead from aqueous media using CMC as an adsorbent. The atomic absorption spectrometric technique was used to determine the distribution of lead. Maximum adsorption was observed at both pH 4 and 5. The adsorption data followed both Freundlich and Langmuir isotherms. Langmuir isotherm gave a saturated capacity of 322.6+/-1.2mg/g at pH 4. From the FTIR spectra analysis, it was concluded that xanthate and amino group participate in the adsorption process. The developed procedure was successfully applied for the removal of lead ions from real battery wastewater samples.     

Pseudomonas aeruginosa immobilized multiwalled carbon nanotubes as biosorbent for heavy metal ions

Pseudomonas aeruginosa immobilized multiwalled carbon nanotubes has been used as biosorbent for the solid phase extraction of some heavy metal ions in environmental samples. Cobalt(II), cadmium(II), lead(II), manganese(II), chromium(III) and nickel(II) ions have been selected as analytes for the presented study, due to their important negative and positive roles in human life. In order to investigate quantitative biosorption conditions of the analytes, the influences of pH of the aqueous solution, eluent type, eluent volume, samples volume, etc. were examined. The effects of alkaline, earth alkaline and some transitions metals on the biosorption of analyte ions on P. aeruginosa immobilized multiwalled carbon nanotubes were also investigated. The presented biosorption procedure was applied to the determination of analytes in tomato leaves, bovine liver, boiled wheat, canned fish, black tea, lichen and natural water samples.     

Lime enhanced chromium removal in advanced integrated wastewater pond system

The removal of trivalent chromium from a combined tannery effluent in horizontal settling tanks and subsequent Advanced Integrated Wastewater Pond System (AIWPS) reactors was investigated. The raw combined effluent from Modjo tannery had pH in the range of 11.2-12. At this pH, a trivalent chromium removal of 46-72% was obtained in the horizontal settling tanks after a one-day detention time. Trivalent chromium precipitated as chromium hydroxide, Cr(OH)3. 58-95% Cr(III) was removed in the advanced facultative pond (AFP) where the water column pH of 7.2-8.4 was close to pH 8, which is the optimum precipitation pH for trivalent chromium. Chromium removals in the secondary facultative pond (SFP) and maturation pond (MP) were 30-50% and 6-16%, respectively. With Cr(III) concentration of 0.2-0.8 mg/l in the final treated effluent, the AIWPS preceded by horizontal settling tanks produced effluent that could easily meet most of the current Cr(III) discharge limits to receive water bodies.     

Competitive biosorption of phenol and chromium(VI) from binary mixtures onto dried anaerobic activated sludge

The ability of dried anaerobic activated sludge to adsorb phenol and chromium(VI) ions, both singly and in combination, was investigated in a batch system. The effects of initial pH and single- and dual-component concentrations on the equilibrium uptakes were investigated. The optimum initial biosorption pH for both chromium(VI) ions and phenol was determined as 1.0. Multi-component biosorption studies were also performed at this initial pH value. It was observed that the equilibrium uptakes of phenol and chromium(VI) ions were changed due to the presence of other component. Adsorption isotherms were developed for both single- and dual-component systems at pH 1.0, and expressed by the mono- and multi-component Langmuir, Freundlich and Redlich–Peterson adsorption models and model parameters were estimated by the non-linear regression. It was seen that the mono-component adsorption equilibrium data fitted very well to the non-competitive Freundlich and Redlich–Peterson models for both the components while the modified Freundlich model adequately predicted the multi-component adsorption equilibrium data at moderate ranges of concentration. The results suggested that the cells of dried anaerobic activated sludge bacteria may find promising applications for simultaneous removal and separation of phenol and chromium(VI) ions from aqueous effluents.     

The action of chromium(III) in fixation of animal tissues

Summary Chromic salts have been studied as fixatives of mammalian tissues for light microscopy, and the binding of the metal has been examined histochemically. Tissues bind chromium(III) from aqueous solutions less acid than pH 2.5; the metal attaches mainly to collagen and basement membranes. Solutions containing chromium(III) as the only active ingredient cannot be used as fixatives because they destroy cytoplasm and cause great structural distortion. When mixed with other fixative agents, however, chromic salts can bring about considerable improvement in structural preservation. In aqueous mixtures more acid than pH 2, and in aqueous-methanolic solutions in the pH range 4.0–5.3, a chromic salt provides only a nonspecific osmotic effect: little or no metal is bound to the tissue, and an aluminium or a sodium salt can be effectively substituted. In less acid (pH 2.3–3.2) aqueous mixtures, the beneficial action of chromium(III) cannot be imitated by aluminium or sodium ions.Chromium(III) forms coordinate bonds that cross-link ionized carboxyl groups of macromolecules. The reaction occurs so slowly that such cross-links can internally strengthen a tissue only after the structure has been stabilized by rapidly acting fixative agents. Thus, a valuable future use of chromic salts may be in a post-fixation treatment to protect specimens against the adverse effects of embedding in paraffin wax. Chromium(III) might also be useful for enhancing the opacity of collagen fibrils in electron microscopy.Address until 30 June 1986: Department of Anatomy and Cell Biology, University of Sheffield, Sheffield, S10 2TN, UK     

Start-up procedures and analysis of heavy metals inhibition on methanogenic activity in EGSB reactor

The effectiveness of operating an industrial UASB reactor, treating wastewater from the beer industry, with flows containing heavy metals was evaluated. A pilot-scale UASB reactor, already used to simulate the industrial reactor, was unsuccessfully employed. An easy start-up was obtained arranging it as an EGSB reactor. Considerations about this modification are reported. The effects of Cu(II), Ni(II) and Cr(III) ions on the anaerobic activity were analyzed by measurements of methane production rate and COD removal. The employed biomass was the sludge of the industrial UASB reactor, while a solution of ethanol and sodium acetate with COD of 3000 mg/L and a heavy metal concentration of 50 mg/L were continuously fed. Experimental results proved higher biomass sensitivity for copper and much slighter for nickel and chromium. Moreover, copper inhibition has been demonstrated to be less significant if a metal-free feed was provided to the system before copper addition.