Chromium Sorption Research Articles

Adsorption of chromium (VI) from aqueous solution by sugar beet bagasse‐based activated charcoal

Chromium (VI) is known to be potentially carcinogenic and mutagenic in humans. A low‐cost industrial solid bioadsorbent, bagasse‐based activated charcoal (BAC), has been investigated for removal of chromium from aqueous solution. All the experiments were carried out in batch process with laboratory‐prepared samples to study the effects of adsorbent dose, contact time, pH and initial concentration of Cr(VI). The removal of chromium ion was found to be highly dependent on the pH of the solution, adsorbent dose and contact time. Also the equilibrium adsorption was analyzed by the Freundlich and Langmuir isotherm models. It was found that the Freundlich isotherm model best described the sorption of chromium by sugar beet bagasse‐based activated charcoal (r2 > 0.9927). Experimental data of kinetic studies were fitted to pseudo‐first‐order, pseudo‐second‐order and modified pseudo‐first‐order models. The results showed pseudo‐second order kinetics was best fitted to the collected data (r2 > 0.9893). Optimum conditions for adsorption were determined at pH 2 and a contact time of 180 minutes (92.7% removal). These retention capacities suggest that BAC can provide a simple, effective, and cheap method for removing Cr(VI) ions from effluents and water resources.

Investigations of Chromium(III) and (VI) Ions Sorption οn SIR by using Photoacoustic and DRS Methods

Chromium is a major pollutant for the environment, usually as a result of some industrial pollution. Chromium is used in various industries such as metallurgical (steel, ferrous and nonferrous alloys), refractories (chrome and chrome-magnesite), and chemical (pigments, electroplating, tanning). For this reason, significant amounts of chromium pass into the environment and cause adverse ecological effects. In the present paper the investigations of solvent impregnated resin preparation was conducted. Photoacoustic and diffuse reflectance spectra were recorded for the prepared solvent impregnated resin. Photoacoustic spectra in the infrared area allow distinguishing the differences between the sorbent applied before and after the impregnation process. Impregnation of resin is a result of physical sorption of Aliquat 336 on macroporous Amberlite XAD 16.

Chromium (III) sorption from aqueous solutions using activated carbon prepared from cashew nut shells

Activated carbon prepared from cashew nut shells using potassium hydroxide activation at 850°C in N2 and CO2 atmosphere was used as an adsorbent for the removal of chromium ions from aqueous solutions. The adsorption of Cr(III) ions on activated carbon was studied. The effect of experimental parameters such as, pH of initial concentration of Cr(III) solutions, contact time, dosage of adsorbent and initial concentration of Cr(III) solutions was investigated. The Freundlich and Langmuir isotherm fitted well to data of Cr(III) adsorption. Cr(III) uptake capacity was 13.93 mg/g which was calculated from the Langmuir isotherm. Key words: Activated carbon, cashew nut shell, trivalent chromium (Cr(III)), adsorption.

Removal of chromium(III) by cation exchange resin, Indion 790 for tannery waste treatment

Extraction of chromium(III) from a model solution and from a tannery waste solution was studied by ion exchange using Indion 790 resin which is a macro-porous strongly acidic cation exchange resin of sulfonated polystyrene group. The resin was found to be selective for the sorption of chromium(III) in the pH range 0.5–3.5 from a model solution containing 500 ppm Cr(III). Beyond pH 3.5 extraction of chromium(III) drastically decreased from 92% to 76%. Sorption of chromium(III) on Indion 790 followed the Freundlich isotherm with a high Freundlich constant value ( K f = 8.57) confirming strong chemical interaction of the metal ion with the resin. Desorption of chromium(III) from the loaded resin increased with the increase in concentration of eluant (5–20% H 2SO 4). With 20% sulfuric acid solution 89% Cr(III) was eluted in two stages. The bench scale results were also validated in continuous mode in a fixed bed column and for the recovery of chromium(III) from a tannery solution.

Sorption of chromium (III) from aqueous solution using bentonitic clay

A local clay from Jebel Chakir (northwest of Tunis, Tunisia, North Africa) has been characterized. The mineralogical and chemical compositions of the materials were determined by X-ray diffraction (XRD), infrared spectroscopy (IR) and by the inductively coupled plasma technique (ICP). The cation exchange capacities (CEC) as well as the surface area were determined using the adsorption isotherm obtained with methylene blue. The specific surface area (SE) was calculated by applying the BET equation to the nitrogen adsorption isotherm at 77 K. The results show that the material is a smectite with a small proportion of kaolinite. The CEC and SE values for the natural fraction are 50 meq /100 g, 48.95 m2 /g respectively for the fired clay; and 77 meq /100 g and 76.78 m2/g for the Na-purified fired clay fraction. The adsorption properties of the natural clay and the Na-purified clay in a chromium rich aqueous solution have been studied by the batch technique. The amount of adsorbed chromium ions, Q, was determined for the adsorption systems as a function of the contact time, the pH, the sorbent, and the metal ion concentration. The results show that the uptake of Cr (III) at pH 4, by the purified clay is very rapid. The quantity removed from the solution reached a maximum value 15 min after mixing, and 1 h for the natural clay although the latter removes greater quantities of Cr (III) ions compared to the Na-purified clay. The amounts sorbed by the natural clay were about 117.5 mg of chromium per gram of clay and 61.4 per gram with the Na-purified clay. Moreover, the results show that the adsorption behaviour of both clays depended highly on the pH. The adsorption increased with the pH of the suspension in the range [3–5.3]. The pH was limited to values equal or less than 5.3 because of the precipitation of the hydroxide chromium at higher pH. The experimental data points have been fitted to the Langmuir and Frendlich models. They are well fitted to the linearized Freundlich isotherm for the natural clay and Langmuir model for the Na-purified clay.

Biosorption of chromium (III) by orange ( Citrus cinensis) waste: Batch and continuous studies

The present study explores the ability of orange waste biomass to remove Cr (III) from aqueous solutions. Batch kinetic and isotherm studies were carried out on a laboratory scale to evaluate the adsorption capacity of orange waste. The effects of particle size, adsorbent dose and solution pH on Cr (III) removal were also studied. The results showed that the higher the adsorbent dosage and the pH, the higher the percentage of metal removal. No significant influence of particle size on sorption capacity was observed in the experimental conditions studied. A kinetic study revealed that the adsorption of Cr (III) onto orange waste was a gradual process and equilibrium was reached within 3 days. A pseudo-second order model was the most appropriate to describe the kinetic experimental data. Equilibrium assays displayed a maximum sorption capacity ranging from 0.57 mmol/g to 1.44 mmol/g when the pH increased from 3 to 5, according to the Sips model, which along with the Redlich–Peterson equation, is very suitable for correlating equilibrium data. The use of the studied adsorbent in the removal of chromium in continuous mode was successful and the breakthrough curves were adequately represented by BDST model. Due to the slow kinetics of chromium sorption onto orange waste, the sorption capacity in batch assays was higher than that in continuous assays.

Adsorption of Cd(II), Cr(III) and Mn(II) on natural sepiolite

Heavy metals such as cadmium, chromium and manganese are toxic priority pollutants that commonly interfere with the beneficial use of wastewater for irrigation and industrial applications. The sorption of cadmium, chromium and manganese from aqueous solutions onto natural sepiolite has been studied. The efficiency of sepiolite as an adsorbent for the removal of these heavy metals from aqueous solutions has been determined. The adsorption was carried out using a batch method. Adsorption data have been interpreted in terms of Langmuir and Freundlich equations. The results were provided strong support for the adsorption of heavy metals into sepiolite. For investigation of exchange equilibria different amounts of sepiolite were contacted with a fixed volume of a heavy metal bearing solutions. Because the uptake of these heavy metals is mainly dominated by the pH of the liquid phase the pH value was varied between pH 0–3 and 0.5–5 g in each series of samples. The initial and final concentrations of heavy metals were determined by means of atomic absorption spectrophotometry. All the operations were conducted at room temperature (20±1°C). Exchange equilibria have been evaluated for sepiolite by means of the surface complex formation theory. For evaluation of equilibrium parameters the generalized separation factors were calculated from experimental data and plotted vs. the respective dimensionless sepiolite loadings. The experiments demonstrated that Cr 3+ and Cd 2+ ions were more efficiently adsorbed than Mn 2+ ions by sepiolite.

Kinetics of hexavalent chromium sorption on amino-functionalized macroporous glycidyl methacrylate copolymer

Two samples of macroporous crosslinked poly(glycidyl methacrylate- co-ethylene glycol dimethacrylate), poly(GMA- co-EGDMA), with different porosity parameters were synthesized by suspension copolymerization and functionalized with ethylene diamine and diethylene triamine. The kinetics of Cr(VI) sorption by amino-functionalized poly(GMA- co-EGDMA) was investigated under non-competitive conditions. Competitive kinetics was studied from following multicomponent solutions: Cu(II) and Cr(VI); Cu(II), Co(II), Cd(II) and Ni(II); Cr(VI), Cu(II), Co(II) and Cd(II) solutions. Two kinetic models (the pseudo-first and pseudo-second-order) were used to determine the best-fit equation for the metals sorption by poly(GMA- co-EGDMA)-en and poly(GMA- co-EGDMA)-deta.

Chromium (III) uptake by agro-waste biosorbents: Chemical characterization, sorption–desorption studies, and mechanism

Within their complex structure, agro-waste materials such as sorghum straw (SS), oats straw (OS) and agave bagasse (AB) have functional groups (i.e. carboxyl and phenolic) that play a major role in metals sorption. The advantages of these materials include availability, low-cost, and a reasonable metal sorption capacity. These agro-waste materials were chemically characterized by acid-base titrations and ATR-FTIR analyses in order to determine their functional groups, equilibrium constants, and surface charge distribution. Batch experiments were conducted at pH 3 and 4, at 25 °C and 35 °C to determine the biosorbents chromium (III) sorption capacity. Partially saturated biosorbents were desorbed with HNO 3, NaOH, and EDTA at different concentrations and temperatures (25 °C, 35 °C, and 55 °C). Finally, the chromium (III) sorption mechanism was discussed. Agro-waste materials functional groups are associated, in part, to carboxyl and hydroxyl groups: these oxygen-containing sites play an important role in the chromium (III) removal. The maximum chromium (III) sorption capacity was 6.96, 12.97, and 11.44 mg/g at pH 4 for acid-washed SS, OS, and AB, respectively. The chromium (III) sorption capacity decreased at pH 3 because H + ions competed for the same functional groups. On the other hand, an increase in temperature enhanced both the biosorbents chromium (III) sorption capacity and their desorption by EDTA. The most probable chromium (III) sorption mechanisms were ion exchange and complexation. The agro-waste materials studied herein efficiently remove chromium (III) from aqueous solution and, most importantly, EDTA can efficiently desorb Cr (III) from agro-waste materials at 55 °C.

Selective recovery of Cr and Cu in leachate from chromated copper arsenate treated wood using chelating and acidic ion exchange resins

The purpose of this study was to selectively remove chromium and copper from CCA-treated wood acid leachates (initial concentrations of 447–651 mg As l −1, 374–453 mg Cu l −1 and 335–622 mg Cr l −1) using ion exchange resins and precipitation techniques. Batch experiments revealed that the chelating resin Dowex M4195 had a high copper selectivity in the presence of chromium while the Amberlite IR120 resin had a high chromium sorption capacity. Combining M4195 and IR120 resins in four successive columns, made with Plexiglas tube, led to 96% copper extraction and 68% chromium extraction. NH 4OH (4 M) efficiently eluted copper from the chelating resin while H 2SO 4 (10% v/v) was used for IR120 resin elution. Copper and chromium recovery by elution reached 94% and 81%, respectively. Successive sorption and elution steps using M4195 and IR120 ion exchange resins presented similar metal removal capacities over the five cycles. No resin deterioration was observed but the results suggested arsenic bulk diffusion into the M4195 resin. Successive treatments of CCA-treated wood leachate with M4195 and IR120 allowed for copper and chromium removal while arsenic could be extracted by coagulation treatment with ferric chloride and precipitation with Ca(OH) 2 at pH 5.7. This final process led to 99.9% arsenic removal. The final effluent contained less than 1 mg l −1 of arsenic, chromium and copper.

Chromium(VI) sorption from dilute aqueous solutions using wool

Removal of chromium(VI) from a dilute aqueous solution was investigated using the sorption technique. Locally available wool from merino sheep was used as an sorbent for the removal of chromium(VI). The influence of operating parameters such as sorbent amount, contact time, pH and initial metal concentration in solution on the sorption capacity were studied in a batch system. Optimum conditions for sorption were determined as wool amount, 50 g L-1; pH 2; and contact time, 20 min. It was seen that when initial metal concentration in solution was increased, the uptake of Cr(VI) increased. Chromium(VI) sorption for different types of wool was also examined. Kinetic data were processed using the intraparticle diffusion model. The results suggest that the Cr(VI) uptake process seems to be controlled by external mass transfer at earlier stages and by intraparticle diffusion at later stages.

An evaluation of chromium and zinc biosorption by a sea weed (Sargassum sp.) under optimized conditions

Biosorption is a promising alternative method to treat industrial effluents, mainly because of its low cost and high metal binding capacity. In this work, Zinc and Chromium biosorption process by Sargassum sp. seaweed biomass was studied. The work considered the determination parameters of Zinc and Chromium sorption such as pH, temperature, agitation speed and biomass size. The optimum conditions were: pH3, temperature (303k) room temperature, biomass size 0.5mm and agitation speed 150rpm. The maximum uptake of Chromium and Zinc is 65% and 53% respectively. The kinetic study revealed that the adsorption of Chromium and zinc by Sargassum sp . fitted the Langmuir isotherm.

Studies on chromium(III) removal from aqueous solutions by sorption on Sphagnum moss peat

Batch sorption experiments were performed for the removal of chromium(III) ions from aqueous solutions using Romanian Sphagnum moss peat (untreated and treated with NaCl solution) as sorbent. In order to establish the best conditions for the sorption of chromium(III), the influence of initial pH, contact time, peat dose and metal ion concentration was investigated. The Freundlich, Langmuir and Dubinin-Radushkevich models were applied to describe the sorption isotherms and to calculate its constants. The experimental data fitted well to the Langmuir model with a maximum sorption capacity of 18.6 mg Cr(III)/g of peat. The mean free energy of sorption suggests that the binding of Cr(III) on peat occurred through an ion exchange mechanism. The kinetic data evaluated by pseudo-first order and pseudo-second order kinetic models showed that the sorption of chromium onto the peat followed a pseudo-second order rate equation. The chromium(III) could be easily eluted from the loaded peat using 0.10 M HCl and the peat may be reused in several sorption/ desorption cycles. The experimental results indicated the potential of Sphagnum moss peat for removal of Cr(III) from wastewaters.

THE BALL MILLING EFFECT ON TRIBASIC CALCIUM PHOSPHATE AND ITS CHROMIUM (VI) ION SORPTION PROPERTIES

The ball milling effect on the sorption properties of tribasic calcium phosphate (TCP) is presented. The materials obtained were characterized by X-ray diffraction, SEM, particle size and specific surface area. The specific surface area of the prepared TCP prepared sample was 60.55 m2/g and unexpectedly decreased to 12.57 m2/g for samples where milling time was 15 hrs. In TCP samples with a milling time of 5 and 10 h, the specific surface values also diminished to 16.81 and 15.11 m2/g, respectively. Fe atoms were found in the milled TCP samples as XRD and EDS techniques revealed. An increase of Cr(VI) ion sorption with milling time was observed with a maximum chromium sorption of 14.0 x 10-4meq/g. This increasing Cr(VI) sorption may be due to the presence of the Fe atoms found in the milled TCP samples.

Sorption of Chromium Ions from Aqueous Solution onto Chemically Activated Carbons Developed from Maize Cobs

Chemically activated carbons were prepared from maize cobs, using phosphoric acid of variable concentration. The textural parameters of the activated carbons were determined from the nitrogen adsorption isotherms measured at 77 K. The chemistry of the carbon surface was determined by measuring the surface pH, the pHPZC and the concentration of the carbon - oxygen groups of the acid type on the carbon surface. Kinetics of Cr(VI) sorption/reduction was investigated at 303 K. Two processes were investigated in terms of kinetics and equilibrium namely; Cr(VI) removal and chromium sorption were studied at various initial pH (1-7). Removal of Cr(VI) shows a maximum at pH 2.5. At pH<2.5, sorption decreases because of the proton competition with evolved Cr(III) for ion exchange sites. The decrease of sorption at pH>2.5 is due to proton insufficiency and to the decrease of the extent of Cr(VI) reduction. The chemistry of the surface of activated carbon is an important factor in determining its adsorption capacity from aqueous solutions particularly when the sorption process involves ion exchange.

Sorption isotherms and kinetics of chromium uptake from wastewater using natural sorbent material

Chromium (VI) which exists in many industrial wastewater is considered highly toxic. The aim of the present investigation was to study the reduction of chromium (VI) to chromium (III) and then removing it with the help of weathered basalt andesite products. Reduction of the chromium (VI) to chromium (III) by hydrazinium sulfate was investigated. The influence of hydronium ion concentration, contact time, hydrazinium sulphate dosage and temperature has been tested in batch runs. The process was found to be acid, temperature and concentration dependent. The suitability of weathered basalt andesite products as a potential sorbent was assessed for the removal of chromium (III) following batch mode of operation. The effect of various parameters such as hydronium ion concentration, shaking time, sorbent dose, initial metal ion concentration and temperature on the removal of chromium (III) from aqueous solution was studied. Thermodynamic parameters (?H°, ?S° and ?G°) for the sorption process were evaluated. Analysis of sorption obtained results showed that the sorption pattern followed the Freundlich, Langmuir and Dubinin-Kaganer-Radushkevich isotherms. The process follows pseudo second order rate and surface diffusion is identified as the predominating mechanism. The sorption process was shown to be reversible by the recovery of sorbed chromium (III) upon extraction with 0.5 M nitric acid. The sorbent, before and after sorption, was characterized by fourier transform infrared spectrometer, X-ray diffraction, scanning electron microscope, transmision electron microscope and thermogravimetric analyse methodes. An increase in crystallanity after sorption of chromium was observed. An industrial effluent was successfully treated with the same sorbent with convincing results.

Effect of Electrochemical Reduction and Oxidation of a Viscose Rayon Based Activated Carbon Cloth for Cr(VI) Sorption from Aqueous Solution

A viscose rayon based activated carbon cloth (ACC) was electrochemically reduced and oxidized to enhance its anion and cation sorption capacity for comparison with the as-received ACC. ACCs were characterized by chloride capacity measurement, sodium capacity measurement, pH titration, elemental analysis, Brunauer−Emmet−Teller surface area measurement, Fourier transform infrared spectroscopy analysis and scanning electron microscopy. Batch sorption experiments showed that chromium(VI) sorption capacity of electrochemically reduced ACC increased 2.12 times at solution pH 4 and chromium(VI) sorption capacity for electrochemically oxidized ACC increased 11.35 times at solution pH 8. The highest chromium(VI) sorption capacity was obtained on electrochemically reduced ACC at solution pH 4 (i.e., 3.8 mmol/g). Chromium(VI) sorption decreased with an increase in solution pH for electrochemically reduced ACC, while it increased with an increase in solution pH for electrochemically oxidized ACC. Chromium(VI) ions were sorbed onto ACCs by ion exchange.

Sorption capacity of new cation exchangers based on oil residue and epoxy resin for chromium(III) ions

Sorption of chromium(III) ions by cation exchangers based on oil residue and ED-20 epoxy resin was studied in comparison with that of KU-2 × 8 industrial cation exchanger.

Waste-activated sludge (WAS) as Cr(III) sorbent biosolid from wastewater effluent

A biological sludge – waste-activated sludge (WAS) – from a dairy filtering station was investigated for the removal of trivalent chromium from aqueous solution. Kinetic results revealed that chromium adsorption was instantaneous. The removal rate increases up to pH 4 for contact times beyond 20 min. The equilibrium state is attained in 30 min in all the considered systems. The reaction orders as well as the diffusion rate constant were determined. Values adsorption isotherms measured at pH 3 generally followed the Langmuir model. The maximum uptake capacity was 25.64 mg/g. Values of thermodynamic parameters show that chromium (III) sorption on WAS is an exothermic process. This study provides an opportunity for the removal of heavy metals such as chromium from aqueous solutions using a low-cost biosolid as adsorbent support.

Sorption of Cr(VI) ions on two Lewatit-anion exchange resins and their quantitative determination using UV–visible spectrophotometer

The sorption of Cr(VI) from aqueous solutions with macroporous resins which contain quarternary amine groups (Lewatit MP 64 and Lewatit MP 500) was studied at varying Cr(VI) concentration, adsorbent dose, pH, contact time and temperature. Batch shaking sorption experiments were carried out to evaluate the performance of Lewatit MP 64 and Lewatit MP 500 anion exchange resins in the removal of Cr(VI) from aqueous solutions. The concentration of Cr(VI) in aqueous solution was determined by UV–visible spectrophotometer. The ion exchange process, which is dependent on pH, showed maximum removal of Cr(VI) in the pH range 3–7 for an initial Cr(VI) concentration of 1 × 10 −3 M. The optimum pH for Cr(VI) adsorption was found as 5.0 for Lewatit MP 64 and 6.0 for Lewatit MP 500. The maximum Cr(VI) adsorption at pH 5.0 is 0.40 and 0.41 mmol/g resin for Lewatit MP 64 and Lewatit MP 500 anion exchangers, respectively. The maximum chromium sorption occurred at approximately 60 min for Lewatit MP 64 and 75 min for Lewatit MP 500. The suitability of the Freundlich and Langmuir adsorption models was also investigated for each chromium–sorbent system. The uptake of Cr(VI) by the anion exchange resins was reversible and so it has good potential for the removal of Cr(VI) from aqueous solutions. Both ion exchangers had high bonding constants but Lewatit MP 500 showed stronger binding. The rise in the temperature caused a slight decrease in the value of the equilibrium constant ( K c) for the sorption of Cr(VI) ion.