Chromium Sorption Research Articles

Treatment of chromium(vi) waste by the non‐living biomass of water hyacinth roots

The potential of the biomass of non‐living water hyacinth roots Eichhornia crassipes, as a biosorbent for Cr(VI) from synthetic solution and electroplating waste was investigated under batch conditions. Various factors affecting sorption of chromium were studied. They include effect of pH, initial concentration, dosage, agitation rate, temperature and the presence of other anions. The optimum pH for the sorption was found to be 2.0 and sorption decreased rapidly as the pH of the solution was increased. Data obtained from sorption isotherms conformed to Langmuir sorption model which implied a monolayer coverage and the maximum sorption capacities of Cr(VI) were 8.93 and 8.92 mg/g for synthetic solution and electroplating waste respectively. A continuous flow study showed that water hyacinth root was effective in removing Cr(VI) from electroplating waste.

Chromium (VI) sorption on quaternized rice hulls

The sorption of Cr(VI) from synthetic solution and electroplating waste by quaternized rice hulls was investigated under laboratory conditions to assess its potential in removing Cr(VI). The results show that quaternized rice hulls provided higher sorption capacity and a more workable pH range as compared to the untreated rice hulls. From the Langmuir isotherm the maximum sorption capacity of Cr(VI) was 32.3 mg/g at pH 4.82 at 25° C. Column studies showed that Cr(VI) and Cu(ll) from electroplating waste could be successfully removed or reduced using a combination of untreated and quaternized rice hulls. The effect of different anions on the sorption capacity of quarternized rice hulls was discussed.

Chromium(III) Removal by Epoxy-Cross-Linked Poly(ethylenimine) Used as Gel-Coat on Silica. 1. Sorption Characteristics

Poly(ethylenimine) has been gel-coated on high surface area silica and insolubilized by cross-linking with a low molecular weight diepoxide (epoxy equivalent 180 g). The resulting granular sorbent shows several times higher sorption than the commercial chelating resin Chelex-100 in chromium(III) sorption from sulfate solution, the respective saturation capacities being 3.2 and 0.95 mmol of Cr(III)/g of dry resin. The sorption of Cr(III) from its chloride solution is less on both the resins, the saturation levels being 0.62 and 0.78 mmol/g of dry resin, respectively. The sorption of Cr(III)/Cl{sup {minus}} on both these sorbents is, however, enhanced significantly by NaCl, the effect being more marked for the gel-coated resin, which shows more than 100% increase in Cr(III) sorption from 0.5 M NaCl solution containing Cr(III) in low concentrations. Both the gel-coated PEI and Chelex-100 show fast kinetics, the t{sub 1/2} values in Cr(III) sorption being 45 and 30 s, respectively. However, the Cr(III) sorbed on Chelex-100 cannot be stripped at ambient temperature even with concentrated HCl while, in contrast, the gel-coated PEI is stripped very easily, the t{sub 1/2} value in 4 N HCl being only 25 s.

Removal of Lead and Chromium by Activated Slag—A Blast-Furnace Waste

The blast-furnace waste generated in steel plants has been converted into a low-cost adsorbent. The resulting activated slag has been characterized and used for the removal of lead and chromium. The effect of pH, sorbent dosage, adsorbate concentrations, presence of other metal ions, temperature, and contact time on the sorption of lead and chromium were studied in batch experiments. Kinetic studies were undertaken to have an idea of the mechanistic aspects of the process. The uptake of lead is found to be greater than that of chromium. Adsorption on activated slag follows both Freundlich and Langmuir models. In addition, a series of fixed-bed experiments were performed in an attempt to simulate industrial conditions. The bed-depth-service-time (BDST) model proposed by Hutchins was successfully applied to the sorptive removal of lead. Some experiments were also performed with a view to recover Pb²\u+ and chemically regenerate the spent slag columns in situ.

Sorption of Trivalent Chromium from Tannery Waste by Moss

The sorption of Cr(III) from synthetic solution and tannery waste using moss, Calymperes delessertii Besch, was conducted under laboratory conditions to assess its potential in removing Cr(III). Parameters investigated include pH, contact time, initial concentration and sorbent dosage. Results obtained from isotherm studies show that the sorption of Cr(III) by moss followed the Langmuir isotherm and the maximum sorption capacities were 15.4 and 13.7 mg g−1 for synthetic solution and tannery waste respectively.

Study of sorption of chromium(VI) ions by fibre anion-exchangers

Sorption of chromium(VI) ions by fibre anion-exchangers containing pyridine, imidazole, hydrazidine, and aliphatic amino groups was investigated. It was shown that the basicity of the sorbents has almost no effect on their selectivity in absorption of chromium ions from solutions. The fibres with pyridine and imidazole groups have higher distribution coefficients, and their capacity for chromium ions is 130 and 120 mg/g, respectively. Sorption of chromium(VI) ions by the fibre sorbent with pyridine groups also corresponds to a mixed diffusion mechanism in dynamic conditions and the internal diffusion coefficient is 3.10−10 cm2/sec. Fibres with low-basicity pyridine groups are resistant to the oxidizing effect of chromium(VI) ions and their exchange capacity is preserved in repeated sorption-desorption cycles. Conversion of pyridine groups to the form of a strong base decreases the chemical stability of the sorbent in absorption of chromium(VI) ions from solutions.

Effect of deacetylation on sorption of dyes and chromium on chitin

Deacetylated chitins (10.7-67.2fl ) were prepared by alkaline hydrolysis to determine an optimal degree of deacetylation (DD) which can effectively remove four dyes and chromium ions from textile effluent. Sorption isotherms were carried by varying the treatment time, pH, and initial concentration of dyes or chromium ions. Experimental results were analyzed in three ways: (1) equilibrium sorption capacity and sorption rate constant, (2) Langmuir isotherms, and (3) separation factor. Results indicated that except for the chitin with a 67.2% DD, rate and capacity of the dye sorption on the chitin increased with the increase of the DD in chitin for each pH but decreased with the increase of pH for each deacetylated chitin. This was mainly due to the increase of-NH 3 + groups in chitin with a high DD and the low pH of the system. On the contrary, dye desorption from the deacetylated chitin was highly effective at 80°C and pH ≥ 10, which could facilitate the reduction of-NH 3 + ions and the increase of electrostatic repulsion. The number of chromium ions sorbed on the chitin also increased with the increase of the DD at a specific time. Therefore, by controlling the DD of the deacetylated chitin maximum efficiency can be achieved in the removal of dyes and metal ions from textile effluent.

Trivalent chromium sorption on alginate beads

The applicability of trivalent chromium removal from aqueous solutions using calcium alginate beads was studied. The equilibrium isotherms were plotted at two temperatures. The relationship between the chromium sorbed and the calcium released was determined as well as the effect of alginate amount and initial pH on the equilibrium results. Chromium sorption kinetics were evaluated as a function of chromium initial concentration and temperature. Transport properties of trivalent chromium on alginate beads were characterised by calculating chromium diffusion coefficients—the Linear Absorption Model and the Shrinking Core Model were assayed. Trivalent chromium removal from aqueous solutions, that made chromium alginate beads by directly dispensing the sodium alginate solution on chromium solutions, was also tested. Finally, a methodology for trivalent chromium removal with alginate is proposed. This method includes two steps: in the first, chromium is removed by using it as an agent for alginate bead formation (for chromium concentrations above 400 mg l −1); afterwards, the obtained solution is placed in contact with previously formed alginate beads for removal of the remaining chromium.

Removal of chromium (III) from aqueous solution using chrome sludge.

The toxicity of chromium to aquatic organisms, mammals and humans has been well documented. At high levels it is reported to be carcinogenic and mutagenic. The main contributing source of chromium to the aquatic environment is from the untreated effluents of tannery, dye, paint, electroplating and textile industries. Various methods for the removal or reduction of chromium from such effluents have been reported. These include reduction followed by precipitation and ion-exchange. These methods are generally expensive. Recently, the use of natural mineral mixtures, hulls and bran and natural fibers for the removal of chromium has been reported. These materials have considerable economical importance because of their low cost and abundant availability. Chrome sludge, a waste material of chrome electroplating processes, has no known commercial value. It is generally stored for indeterminable periods in the vicinity of the plant awaiting treatment or appropriate disposal. In the present study, the sorption of chromium (III) from aqueous solution on chrome sludge was investigated. 6 refs., 6 figs., 1 tab.

A bench-scale study on chromium recovery from tanning wastewater

In order to recover chromium, wastewaters from the chrome-tanning process in two Thai tanneries were coagulated with magnesium oxide or sodium carbonate at various dosages. Different types of polymer were also tried to improve the settleability of the chromium sludge which, in turn, was redissolved by sulfuric acid. The produced chromium III sulfate (Cr2(SO4)3) solution was sufficiently concentrated for direct reuse in the tanning step. The settling pattern of the chromium sludge was also observed and optimum sedimentation periods ranging from 1 to 17 hours were suggested. Under no tanning-additive (a chemical to improve chromium sorption onto hides) circumstances, the discharged wastewater contained 5-11 g Cr2O3/l and the most promising coagulant was MgO at a dose of twice the stoichiometric value and an optimum pH of 7-8. The resulting chromium precipitate or sludge was quite dense (21% solids) and possessed a good settling velocity (234 mm/h), making the decantation process very easy, whereas the corresponding acid requirement for the dissolution process was 1.5 times the stoichiometric value. On the other hand, in the tanning-additive situation, the chromium concentration in the drain was reduced to 3-6 g Cr2O3/l. Magnesium oxide was shown to be also the best coagulant but the dose was two times higher than that of the first circumstance, ie., four times that of stoichiometric requirement.

Clay minerals as sorbents for nuclear reactor activation products

A comparison is presented of cobalt and chromium uptake on different clays. It is shown that clay minerals are good adsorbents for cobalt and chromium in waste effluents. The sorption of cobalt and chromium on the clays studied was by ion exchange and surface complex formation, respectively. In addition, the percentage of either cobalt or chromium removed in a mixed solution environment is higher than the individual adsorption in single-component experiments. This proves a synergistic mechanism. The optimum uptake of each metal ion from mixed species was achieved by montmorillonite clay in the calcium form.

Biosorption of hexavalent chromium by yeasts

Different species of yeast exhibit noticeable differences in their ability to sorb Cr(VI). The sorption ability of dehydrated cells is considerably higher than that of intact cells and optimal sorption of chromium takes place at physiological (30°C) or elevated (45°C) temperatures.

A bench-scale study on chromium recovery from tanning wastewater

In order to recover chromium, wastewaters from the chrome-tanning process in two Thai tanneries were coagulated with magnesium oxide or sodium carbonate at various dosages. Different types of polymer were also tried to improve the settleabiity of the chromium sludge which, in turn, was redissolved by sulfuric acid. The produced chromium III sulfate (Cr2(SO4)3) solution was sufficiently concentrated for direct reuse in the tanning step. The settling pattern of the chromium sludge was also observed and optimum sedimentation periods ranging from 1 to 17 hours were suggested. Under no tanning-additive (a chemical to improve chromium sorption onto hides) circumstances, the discharged wastewater contained 5–11 g Cr2O3/l and the most promising coagulant was MgO at a dose of twice the stoichiometric value and an optimum pH of 7–8. The resulting chromium precipitate or sludge was quite dense (21% solids) and possessed a good settling velocity (234 mm/h), making the decantation process very easy, whereas the corresponding acid requirement for the dissolution process was 1.5 times the stoichiometric value. On the other hand, in the tanning-additive situation, the chromium concentration in the drain was reduced to 3–6 g Cr2O3/l. Magnesium oxide was shown to be also the best coagulant but the dose was two times higher than that of the first circumstance, ie., four times that of stoichiometric requirement.

Long-term intracellular chromium partitioning with subsurface bacteria

Subsurface bacteria were used to study the kinetics of chromate uptake and the internal distribution of the chromium that is taken up by these cells using two equilibration periods (1 and 50 days). Cells that were exposed to chromate for 50 days (to simulate in-situ conditions) were able to sequester up to 200% more chromium per unit mass of cells than were cells that were exposed for only 1 day. Chromium distributions showed an increase in chromium sorption by the cell wall, by the membrane and ribosome, and by the soluble fraction after a 50-day equilibration period compared to after 1 day of equilibration. Killed cell controls suggest that active transport of chromate is the method of intracellular accumulation during the 50-day equilibration period.

Surface and Charge Characteristics of the Oxide/Solution Interface Towards Chromium(VI) Sorption

The interfacial properties of zirconium oxide, titanium oxide and bismuth oxide have been studied under various experimental conditions. The oxides were characterized by means of their pH titration curves, intrinsic dissociation constants [pKai*(intr.), i = 1, 2) and point of zero charge (pHpzc) in varying concentrations of KNO3 and Na2CrO4 solutions. The pHpzc values of all the oxide samples tended to shift to higher pH values in the presence of Na2CrO4 solution and remain the same in the presence of KNO3 solution. A mechanism for the sorption process is proposed proceeding through an exchange with surface OH– or H2O groups and is interpreted as a case of specific adsorption.

Chromium sorption by phlogopite and biotite in acidic solutions at 25°C: Insights from X-ray photoelectron spectroscopy and electron microscopy

Large single crystals of biotite and near endmember phlogopite were reacted with acidic Cr(VI)-and Cr(III)-bearing solutions, at 24–27°C and 1 atm. After reaction of the micas with Cr(VI) solutions, XPS analyses of biotite and phlogopite edges indicated little or no chromium on phlogopite but elevated concentrations of chromium on biotite. The binding energies for Cr2 p are consistent with a Cr(III) species. XPS and SEM of biotites reacted with Cr(VI) solutions indicate that chromium is strongly sorbed by the edges of mica books relative to the basal plane. In fact, much of the chromium associated with the basal plane is sorbed by steps and micron-sized biotite flakes, or, in other words, by layer edges. TEM and SEM of biotite basal planes and edges show no Cr-rich precipitates. After reaction of the micas with a Cr(III) solution at pH = 3, XPS shows similar concentrations of a Cr(III) species on both biotite and phlogopite, and on the edges and basal planes. These results stand in strong contrast to the results from Cr(VI) solutions. XPS indicates that near-surface iron in biotite is more oxidized after reaction with Cr(VI)-bearing relative to Cr(III)-bearing solutions. A comparison of biotites and phlogopites from the Cr(VI) and Cr(III) experiments provides convincing evidence for coupled sorption and reduction of Cr(VI) aq at the biotite edge-fluid interface. Experiments with additions of potassium and sodium perchlorate confirm the importance of potassium in the heterogeneous coupled cation-electron transfer reaction. Initial observations indicate that biotite concentrated Cr(III) more strongly in Cr(VI) solutions than in the Cr(III) solution, at pH = 3 and ionic strength ≈ 10 −3 M, despite the fact that there were orders-of-magnitude more Cr(III) aq in the Cr(III) solution than in the Cr(VI) solutions.

Mechanisms of chromium(III) sorption on silica. 1. Chromium(III) surface structure derived by extended x-ray absorption fine structure spectroscopy

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMechanisms of chromium(III) sorption on silica. 1. Chromium(III) surface structure derived by extended x-ray absorption fine structure spectroscopyScott E. Fendorf, Gerry M. Lamble, Michael G. Stapleton, Michael J. Kelley, and Donald L. SparksCite this: Environ. Sci. Technol. 1994, 28, 2, 284–289Publication Date (Print):February 1, 1994Publication History Published online1 May 2002Published inissue 1 February 1994https://doi.org/10.1021/es00051a015RIGHTS & PERMISSIONSArticle Views683Altmetric-Citations127LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (728 KB) Get e-Alerts Get e-Alerts

Mechanisms of chromium(III) sorption on silica. 2. Effect of reaction conditions

Metal ion retention on solids present in soils and waters decreases the risk of these contaminants as they are removed from the mobile aqueous phase. Determining the stability of the sorbed metal ions and the reaction conditions which influence the structure of the sorbate are necessary to evaluate the environmental risk of the sorbed moieties. In this study, a multitude of molecular level experimental techniques, including diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and high-resolution transmission electron microscopy (HRTEM), were employed to ascertain the Cr(III) surface structure on amorphous SiO 2 (silica) and reaction conditions (pH, solution Cr concentrations, and surface coverage) that affect the sorption mechanism

Chromium removal in tannery wastewaters “polishing” by Pinus sylvestris bark

The possibility of using ground, dried and classified Pinus sylvestris bark for trivalent chromium removal in tannery wastewater “polishing” was studied. Tests were carried out with synthesized solutions whose chromium concentrations (5 and 20 mg/l) were similar to those found in some effluents of Portuguese tannery industries after physico-chemical treatment. Bark concentrations of 1 and 2 g/l were used (higher concentrations would have no practical value) and chromium removals ⩾ 90% were achieved in a 4.5–5.0 pH range. Agitation was accomplished by means of both air bubbling and vibrating plate. Slight differences occurred. Bark wetting was achieved either by simple bark/solution contact or vacuum application. No marked differences were observed. From an industrial point of view air bubbling agitation and simple bark/solution contact certainly look more interesting. The presence of other ions decreased the chromium removal though this decrease was never greater than about 20%. Pretreatments of bark were carried out and, in some cases, an increase of about 6–11% in the chromium sorption capacity of bark was observed.

Biosorption of metals by a waste biomass

AbstractThe binding of several metals by waste biomass of Streptomyces noursei was investigated. With respect to the binding capacity, the following order was observed: Ag > Cr > Pb > Cu > Zn > Cd > Co > =Ni. The sorption of metal ions increased with the increasing initial concentration of metal. The adsorption equilibrium of copper, lead and chromium sorption, and silver sorption at low concentration can be described by the Freundlich and Langmuir models. The possibilities for desorbing the metals from loaded biomass and the repeated use of biomass were investigated. The influence of various ions in water on metal sorption was tested. The metal capacity and selectivity of metal binding by biomass are important qualities for practical use.