Desorption Of Chromium Research Articles

Biosorption and desorption of chromium using hybrid microalgae-activated sludge treatment system

This study utilised a mixed culture of Chlorella vulgaris and bacteria from sludge to treat synthetic tannery wastewater (STWW) in modified stirred-tank photobioreactors (MSTPBRs). The MSTPBRs were fabricated locally and operated at irradiance value of 580 µmol/m2s supplied by red light-emitting diodes at 12:12 light–dark cycles and 100 ± 1 rpm continuous stirring. In each case, 50, 100 and 150 mg/L concentrations of STWW were inoculated with mixed culture of microalgae and bacteria in three MSTPBRs, with the control MSTPBR operating at 50 mg/L of STWW. Chromium concentrations were measured using colorimeter whilst Fourier transform infrared spectroscopy (FTIR) indicated possible Cr biosorption. Maximum Cr (VI) and total Cr removal efficiencies of 93 and 94% were achieved, with more than 78% total Cr recovery. Results from FTIR suggested involvement of Chlorella vulgaris in the Cr biosorption. The hybrid microalgae-bacteria system efficiently treated tannery wastewater with considerable Cr removal efficiencies. The potentials of the system in treating tannery wastewater in larger scale may require further investigation.

Chromium Disarmament from Veritable Tanneries Sewer Water Utilizing Carbonic Rice Straw as a Sorbent: Optimization and Carbonic Rice Straw Characteristics

This exploration focuses on the removal of chromium from actual tannery wastewater, collected from the HARBY TANNERY factory in Rubiki (Badr City), using an economical sorbent made from activated carbon derived from rice straw (CRS). The CRS sorbent is activated using H3PO4. The experiment aims to assess the impact of various parameters, including chromium initial concentration, sorbent dosage, treatment time, agitation velocity (rpm), sorbent particle size, and solution pH, on chromium removal from tannery wastewater. Structural, morphological, and electronic distinctive of raw and treated CRS, as well as carbonized CRS, were analyzed using FTIR, SEM, and TEM techniques. XRF analysis was conducted to investigate the chemical elemental composition of carbonized CRS before and after sorption. Zeta potential measurement was performed to assess the electrical charges of particles present in a suspension. The adsorption data was tested for both Langmuir and Freundlich adsorption isotherms, and most of the factors suggested that it follows the Langmuir adsorption isotherm with an R2 value of 99.67%. Additionally, adsorption kinetics were performed to identify the reaction order, which exhibited that sorption pursued pseudo-second-order kinetics with a rate constant (k) of 0.0658 g/mg g/min, a high correlation factor (R2) of 99.76%, and an estimated equilibrium chromium ion adsorption capacity (qe) of 1.597 mg/g, which closely matched the experimental data (1.4835 mg/g). The improved surface morphology and increased surface area of CRS resulted in approximately 98.9% chromium removal. Mechanism studies confirmed that intraparticle diffusion is not the sole rate-controlling step, and Boyd’s model demonstrated that film diffusion limited the rate of chromium adsorption. The desorption of chromium from the carbonized rice straw surface could be achieved by up to 96.4% of the sorbed amount by raising the solution pH to 10, indicating the potential reusability of carbonized rice straw for additional adsorption cycles. Finally, a statistical regression analysis and least square multivariate analysis were used to establish a correlation for predicting efficiency, yielding an R2 value of 97.54%.

Study of the Removal Efficiency of Chromium Ions Using a Membrane by Electro-Kinetic Technique from Sludge.

Recently, electro-kinetic (EK) remediation has become more popular as a novel method for removing chromium contamination from soil. This approach, however, is ineffective since it uses both cationic and anionic forms of chromium. In this study, a membrane-based technique was employed to increase the efficiency of the electro-kinetic removal of chromium. Chromium removal from polluted sludge was studied using four bench-scale experiments. Two of these experiments employed distilled water (EK-1 and EK-2 and membrane), whereas the other used acetic acid as the catholyte (EK-3 and EK-4 and membrane). The pH, total chromium, and fractionation of chromium in the sludge were measured after remediation. In the EK-1, EK-2 and membrane, and EK-3 and EK-4 and membrane trials, the average removal efficiencies of total chromium were 47.6%, 58.6%, and 74.4%, 79.6%, respectively. In contrast to the electro-kinetic remediation strategy, which left approximately 80% of the sludge neutral or alkaline after treatment, the membrane created acidic soil conditions throughout the sludge. For example, the high field intensity used in the membrane tests may have helped to facilitate chromium desorption, dissolution, and separation from the sludge and enhanced chromium mobility. The findings show that the membrane can improve the effectiveness of chromium removal from sludge when utilized in the EK remediation process.

Chromium Recovery from Chromium-Loaded Cupressus lusitanica Bark in Two-Stage Desorption Processes.

Hexavalent chromium (Cr(VI)) contamination poses serious health and environmental risks. Chromium biosorption has been employed as an effective means of eradicating Cr(VI) contamination. However, research on chromium desorption from chromium-loaded biosorbents is scarce despite its importance in facilitating industrial-scale chromium biosorption. In this study, single- and two-stage chromium desorption from chromium-loaded Cupressus lusitanica bark (CLB) was conducted. Thirty eluent solutions were evaluated first; the highest single-stage chromium desorption efficiencies were achieved when eluent solutions of 0.5 M NaOH, 0.5 M H2SO4, and 0.5 M H2C2O4 were used. Subsequently, two-stage kinetic studies of chromium desorption were performed. The results revealed that using 0.5 M NaOH solution in the first stage and 0.5 M H2C2O4 in the second stage enabled the recovery of almost all the chromium initially bound to CLB (desorption efficiency = 95.9-96.1%) within long (168 h) and short (3 h) desorption periods at each stage. This study clearly demonstrated that the oxidation state of the recovered chromium depends on the chemical nature and concentration of the eluent solution. The results suggest the possible regeneration of chromium-loaded CLB for its subsequent use in other biosorption/desorption cycles.

Adsorption of heхavalent chromium on mechanically activated graphite

Mechanical activation of spectrally pure graphite was carried out in a high-energy planetary mill. Changes in the structure and physicochemical properties caused by this modification are shown by SEM, XRD, Raman spectroscopy, XPS, N2 adsorption-desorption, and inert gas fusion methods. Because of the mechanical activation, a decrease in crystallite size of the graphite and the oxidation occurred; it began to exhibit sorption properties with respect to Cr(VI) ions. The optimal conditions were found for removing more than 99% of Cr(VI) from the 50 mg∙l−1 aqueous solutions. In an acetate buffer solution with pH 6.3 after 1 h of heating at 90°C, the Langmuir adsorption capacity for chromium on this sorbent is 14.7 mg∙g−1. Thermodynamic characteristics of the adsorption were determined; they show that the process is spontaneous and endothermic. It was found that only incomplete desorption of chromium from the surface of the modified graphite is possible using concentrated NaOH solutions. An assumption was made about a mixed mechanism of chromium adsorption, including partial reduction of Cr(VI) to Cr(III), anionic adsorption of Cr(VI) ions through electrostatic interaction, and the formation of an insoluble chemical compound of Cr(III) on the surface of the mechanically activated graphite. The sorbent was tested on a real sample of wastewater from bichromate production, after adsorption hexavalent chromium was not detected in the water.

Removal of Cr(VI) from wastewater by modified montmorillonite in combination with zero-valent iron

For this study, the authors synthesised a composite sorbent based on montmorillonite: (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2·nH2O denoted by MM, that contains Fe3O4 particles and dodecyldimethylbenzylammonium chloride: C21H38NCl as a cationic surfactant (CS) denoted by MM:Fe3O4:CS. X-ray phase analysis showed that the interlayer distance of montmorillonite expanded by 0.3 Å in the process of modification by Fe3O4, and by another 2.5 Å with further addition of the surfactant. The expansion of the interlayer space of MM acts as evidence of the penetration of the modifying particles into the MM structure and the formation of a composite with properties that differ from the initial MM.This modification promotes an increase in the adsorption efficiency of Cr(VI) ions from their 50 mg/L acidic solutions by more than 5 times compared to the initial MM, and up to 2.8 times when compared to MM:Fe3O4 composite. The adsorption of Cr(VI) on MM:Fe3O4:CS is accurately described by the Langmuir model (r2 > 0.99); the maximum Langmuir capacity at pH = 5 and 290 K is 38.8 mg/g. The authors also investigated the thermodynamics of the sorption process; it has been shown that the process is endothermic, the determining factor in it is the structural changes of the sorbent. It has been shown that complete desorption of chromium is possible using a 2 M NaOH solution.The composite sorbent was tested on removing Cr(VI) from a real wastewater sample. It has been shown that purification to the maximum permissible concentration level in drinking water is possible when using a combination of adsorption with post-purification with zero-valent iron sol. On the basis of this combination, a scheme is proposed in this paper for the utilisation of chromium-containing solutions to obtain water of an acceptable quality that can be discharged into surface water, and a chromium-containing solution for the extraction of pure chromium compounds.

Recovery of Cr(III) from Tannery Effluents by Diafiltration Using Chitosan Modified Membranes

The selective recovery of chromium remaining in tannery effluents after the leather tanning process is highly desirable to potentiate its reuse, simultaneously minimizing the ecotoxicity of these effluents. To the best of our knowledge, this work evaluates for the first time the ability of a chitosan-based membrane for selective recovery of chromium from a tannery wastewater by subsequent diafiltration and selective chromium desorption, envisaging their integration after tannery wastewater treatment by reverse osmosis (RO). A polyethersulfone (PES) microfiltration membrane top-coated with a chitosan layer (cs-PES MF022) was used for selective recovery of Cr(III), from concentrate streams obtained by treatment of synthetic and real tannery effluents through reverse osmosis (RO), through a diafiltration process. The diafiltration of the RO concentrates was conducted by an intermittent addition of water acidified to pH 3.6. The prepared cs-PES MF022 membranes were able to retain 97% of the total mass of Cr(III) present in the RO concentrates, from a real tannery effluent, with a selectivity of 4.2 and 5 in reference to NH4+ and Cl−, respectively, 12.9 and 14.6 in reference to K and Na, and >45 in reference to Mg, Ca, and S. Such a high selectivity is explained by the preferential adsorption of Cr(III) onto chitosan, and by the relatively high permeability of cs-PES MF022 membranes to the other ionic species. Proof of concept studies were performed to investigate the desorption of Cr(III) at pH 2 and 5.8. A higher Cr(III) desorption degree was obtained at pH 2, leading to a final solution enriched in Cr(III), which may be re-used in tannery operations, thus improving the process economy and reducing the hazardous impact of the effluents discharged by this industry.

Strategic study of adsorption and desorption of chromium on vertisols and its implication in developing an effective remediation technology

ABSTRACT Chrome tanning in India leads to severe contamination of soil and water. Due to the indiscriminate disposal of effluent from tanneries, several thousand hectares of agricultural lands have been degraded over several decades in Tamil Nadu. Several researchers were involved in developing remediation technologies for chromium contamination.Adsorption and desorption of Cr on soil determine the mobility of Cr and its environmental impact. There are several studies regarding the adsorption/desorption of Cr. A strategic study regarding the mechanism of adsorption/desorption of Cr to the context of remediation technologies is essential. A better understanding of the adsorption and desorption mechanism of Cr aids in developing a suitable remediation strategy. Therefore, in the present investigation, the adsorption Cr on soil and some critical factors affecting the adsorption were studied. The Cr adsorption on soil recorded maximum and was best illustrated by the Freundlich isotherm (R2 = 0.994) than the Langmuir isotherm (R2 = 0.841). Amongst the bio-amendments, biochar was found to enhance the adsorption of Cr on the soil. The co-contaminants such as cadmium and lead significantly reduced the adsorption of Cr. Further, a desorption study was carried out with different desorption agents such as NaOH, CH3COONH4and EDTA. It was found that NaOH exhibited higher desorption efficiency than the other agents. The results reveal that adsorption and desorption mechanisms aids in predicting the toxicity of Cr. This study also shows that the soil pH, bio-amendments, and co-contaminants in the contaminated soil may play a significant role in the remediation process.

Chromium desorption kinetics influenced by the rice husk and almond soft husk modified biochar in a calcareous soil

This study introduced modified biochar to enhance the adesorption isotherms of hexavalent chromium in a calcareous soil. Almond soft husk and rice husk biochars as precursor reagents were applied to prepare the modified biochars with abundant amino groups for heavy metal removal. For this purpose, biochars included levels zero (without biochar or control) and 4 wt% (unmodified biochar and modified biochar). Biochars were modified separately with Fe3O4, NaOH, KOH, H2SO4, and HNO3 and four levels of potassium dichromate (0–150 mg/kg soil) were used. Sampling from the treated soil was carried out 5 months after the contamination of soil with chromium. All treatments (5 g) were extracted with 25 mL of a 0.01 M EDTA solutions. The suspensions were shaken for different time periods (5 to 2880 min) at 150 rpm. Concentration of Cr was analyzed in each extract by atomic absorption spectrophotometer. The results indicated that adding rice husk and almond soft husk biochars to the soil resulted in a decrease in Cr uptake at all extraction times compared to control, whereas the rice husk biochar showed a lower reduction in Cr removal than the control compared to the almond soft husk biochar. Based on the determination coefficient and standard error, the best two-constant rate equations are considered the best predictor of the chromium release kinetics trend in the studied soil.

Sorption and desorption behaviour of chromium in soils of Punjab

The present study was carried out to understand soil chromium (Cr) sorption/desorption phenomena, and hence Cr bioavailability in surface soils collected from Jalandhar, Ludhiana and Mandi Gobindgarh in Punjab. Chromium sorption isotherms were derived by sorption of Cr from solutions containing a range of concentrations equivalent to 50, 100, 300 600 and 900 μg Cr g−1 soil in the presence of a background electrolyte, 0.01 M Ca(NO3)2. Chromium desorption isotherms were derived from the Cr desorbed (μg g1 soil) after each of five desorption periods, carried out by sequentially equilibrating same soil samples used for Cr sorption study in Cr-free 0.01 M Ca(NO3)2. It was observed that with the increase in rate of Cr application, amount of Cr sorbed by the soils also increased; however, the per cent Cr sorbed decreased. The Cr sorption data of the three selected soil samples were best described by Freundlich (R2 = 0.986 to 0.994) followed by Langmuir (R2 = 0.959 to 0.995), and Dubinin-Radushkevich (D-R) adsorption isotherms (R2 = 0.926 to 0.973). The constants measuring adsorption capacity, derived from all the three adsorption isotherms, indicated that the soil from Mandi Gobindgarh has higher Cr sorption capacity than the other two soils. Desorption of Cr as well as per cent Cr desorbed from the selected soils increased with the increase in added Cr concentration. The Cr desorption data of the soils were very well described by Langmuir desorption isotherm (R2 = 0.96 to 0.99). Desorption maxima derived was also observed to be higher in case of Mandi Gobingarh soil which implies that this soil has maximum desorption capacity. The differences in amounts of Cr sorbed and desorbed by experimental soils may be due to variation in soil parameters such as organic carbon and cation exchange capacity.

Desorption of chromium (VI) and lead (II) ions and regeneration of the exhausted adsorbent

The desorption characteristics of previously adsorbed hexavalent chromium [Cr(VI)] and divalent lead [Pb(II)] ions on groundnut husk were tested by various desorption eluents such as tap water, de-ionized water, NaOH, HCl and H2SO4. Among them, HCl and H2SO4 were chosen as the best desorbing agents for Cr(VI) and Pb(II) ions, respectively, due to their high desorption efficiency. The desorption efficiency of HCl and H2SO4 for Cr(VI) and Pb(II) ions was about 76.1% and 82.1%, respectively, at a concentration of 0.1 M for both elution agents. The exhausted groundnut husk was regenerated up to five cycles, and the removal efficiency of Cr(VI) and Pb(II) ions on the recycled groundnut husk could be maintained at 53.5% and 54.6%, respectively, in the third cycle. The successive regeneration cycles resulted in the reduction of the desorption efficiency by 20.0% and 26.7% for Cr(VI) and Pb(II) ions, respectively, after the third cycle. The results show that groundnut husk could be recycled when used to remove Cr(VI) and Pb(II) ions from Cr(VI) and Pb(II)-polluted water and wastewaters.

Removal and desorption of chromium in synthetic effluent by a mixed culture in a bioreactor with a magnetic field

Two chromium removal experiments were performed in bioreactors with and without a magnetic field under the same conditions. The release of the chromium present in the biomass was tested in two experiments one with the initial pH of the medium and one with pH 4.0. The objective was to remove Cr(VI) and total Cr from the effluent, this was carried out by placing biological treatments of synthetic effluent contaminated with 100 mg/L of Cr(VI) in a bioreactor with neodymium magnets that applied a magnetic field (intensity 85.4 mT) to the mixed culture. The removal of Cr(VI) was approximately 100.0% for the bioreactor with a magnetic field and 93.3% for the bioreactor without a magnetic field for 9 hr of recirculation of the synthetic effluent by the bioreactor. The removal of total Cr was 61.6% and 48.4%, with and without a magnetic field, respectively, for 24 hr. The desorption of Cr(VI) in the synthetic effluent was 0.05 mg/L, which is below the limit established by Brazilian legislation (0.1 mg/L) for the discharge of effluent containing Cr(VI) into bodies of water. The results obtained for the removal of chromium in synthetic effluent suggested that there was no significant influence on the viable cell count of the mixed culture. The desorption of Cr(VI) in synthetic effluent after bioadsorption of chromium by the mixed culture in the process of removal of chromium in bioreactors with and without a magnetic field was not significant in either of the experiments with different initial pHs.

Toxicity test of desorbed chromium from polluted soil around tannery industry in Yogyakarta-Indonesia by using Brassica juncea and Helianthus annuus L.

Indonesia’s target to be a new industrial country makes a wide chance in the developing of many industrial sectors. The main problem is the disruption of environmental balance due to poorly managed liquid waste released by the industry. Heavy metal such as chromium (Cr) is the typical pollutant generated from tannery industry in Indonesia. Toxicity test of desorbed chromium ions from polluted soil around tannery industry in Yogyakarta-Indonesia by using Brassica junceaand Helianthus annuus L.has been carried out. In this research, soil samples were dividedinto four sample points based on the distances from the waste water point sources. Metal content and some physico-chemical properties including ash content, total organic carbon, and cation exchange capacity were determined in this study. Furthermore, the chromium ions adsorption and desorption from polluted soils were investigated and measured by atomic adsorption spectrophotometry (AAS). Thus, ecotoxicity testsof soil eluates from desorption experiments wereperformed with Brassica junceaand Helianthus annuus L.The resultsshowed that sample III had the highestCr content at916mgkg–1.The adsorption isotherm of Cr ions into soils followed Langmuir isotherm with the highest maximum adsorption capacity value at 14.286 mg kg-1in the sample point IV (unpolluted soil). The optimum desorption of chromium occurred at pH 3. Toxicity test showed that Cr ions had toxic effect to Brassica junceaand Helianthus annuus L.

Recovery of Chromium(VI) Oxyanions from Aqueous Solution Using Cu(OH)2 and CuO Embedded Chitosan Adsorbents

Owing to its availability, low cost and strong reducibility capacity, chitosan can be widely used for Cr(VI) recovery, in this study the removal of Cr(VI) from aqueous solution was investigated using composite adsorbents derived from chitosan (obtained from shrimp peels) and Cu(OH)2 or CuO (prepared by alkaline precipitation of Cu(II) ions) to manufacture ChiCu(OH)2 and ChiCuO, respectively. The adsorbents were characterized by using SEM, BET surface area and zeta potential measurements. Adsorption uptake was highly dependent on pH, temperature, Cr(VI) concentration and sorbent mass: The optimum pH for Cr(VI) removal being close to 4. The adsorption isotherm can be described by Langmuir adsorption isotherm while the uptake kinetics was highly fitted with the pseudo-second order rate equation. The effect of temperature was also evaluated, verifying the endothermic nature of the adsorption process. Chromium desorption was performed using alkaline saline solution (20 g L−1 NaCl with the pH set to 12 with NaOH). The recycling of the sorbent was tested, maintaining a removal efficiency and a metal recovery over 90% for three successive adsorption/desorption cycles. The results showed that, the fabricated nanocomposites are promising adsorbents for Cr(VI) from aqueous solution.

Adsorption and desorption of chromium with humic acid coated iron oxide nanoparticles.

Presence of carcinogenic chromium, i.e., Cr(VI), in different industrial effluents necessitates design and development of effective abatement technologies. Nanosorbent consisting of iron oxide nanoparticles functionalized with soil-derived humic acid was employed for removal of Cr(VI). The point of zero charge for both humic acid and nanoparticles as estimated from pH shift experiments was between pH8 and 9. Adsorption isotherm from batch experiments at neutral pH followed Langmuir model with projected maximum adsorption capacities for humic acid coated nanoparticles (24.13mg/g) much higher than its uncoated counterpart (2.82mg/g). Adsorption was process very fast and kinetics could be described with pseudo-second-order model (R2 > 0.98), for both nanoparticles. High E4/E6 ratio of extracted humic acid and Fourier transform infrared spectroscopy of coated nanoparticles (20-100nm) indicated enrichment of hydroxyl, carboxylic, and aliphatic groups on surface leading for the better adsorption. Humic acid coated and uncoated nanoparticles regenerated with EDTA, NaOH, urea, Na2CO3, and NaCl treatments retained 35.90-59.67 and 26.37-36.28% of their initial adsorption capacities, respectively, in 2nd cycle. Experimental controls (virgin nanoparticles subjected to an identical regenerating environment) revealed irreversible surface modification as the cause for loss of their adsorption capacities.

Sorption and desorption of chromium from applied tannery sludge in soils under pastures and Cerrado vegetation.

Tannery sludge is often used in agriculture as a source of nutrients and for controlling soil acidity. However, the use of this substance can promote soil contamination by chromium. The objectives of this research were to determine the sorption and desorption isotherms of chromium from tannery sludge in a laboratory experiment. The sorption and desorption of chromium were determined in samples of an Oxisol under pasture and native vegetation (Cerrado). Soil samples were mixed with tannery sludge and a solution of chromium sulfate. The soil samples containing chromium at different concentrations were shaken for 72 hours in cycles of 12 hours of shaking and 12 hours of rest. The samples were then centrifuged, and the soil separated from the supernatant and were subjected to selective desorption with CaCl2, NaOH, and Na2EDTA solutions to determine the different fractions of chromium. Results showed of the chromium retention in the soil was strongly influenced by the soil organic matter and the organic matter from tannery sludge. That chromium presented in both tannery sludge and sulfate was strongly sorbed on soil. Chromium desorption was higher for samples treated with NaOH in the tannery sludge and with others extractors in the sulfate treatment.

Retracted: Effect of the potential difference applied on the removal of chromium by adsorption on activated carbon prepared from biomass waste material

The objective of this study is the removal of chromium from aqueous solution by electrosorption on carbon prepared from lignocellulosic natural residue “date stones” thermally treated at 900 °C by imposing potential differences from -0.1 to -0.5V/SCE. The results make it possible to observe that the adsorption kinetics increased at more negative potentials (-0,5V). Chromium desorption tests were performed by applying positive potential differences. The effect of pH and cycles number on the elestosorption process was studied. The experimental results concluded that the better adsorption efficiency was obtained when pH equal to 10, which is about 98%. Furthermore, it was confirmed that the recycling process of adsorption/desorption could be conducted for several cycles.

Aminopropyl-modified mesoporous silica nanospheres for the adsorption of Cr(VI) from water

Aminopropyl-functionalized mesoporous silica spherical particles were obtained through post-synthetic route. The suitability of this material as an adsorbent for heavy metals from aqueous media was tested by Cr(VI) adsorption experiments performed at various pH conditions, chromium concentrations and time. The synthesized particles were characterized before and after functionalization by X-ray diffraction at low angles, nitrogen adsorption–desorption isotherms, infrared Fourier transform spectroscopy, scanning electron microscopy and thermogravimetric analysis. It was found that Cr(VI) adsorption occurs more efficiently in the pH range between 2 and 3. As a consequence of the nanometer scale of the particles, concentration profiles do not develop inside of them and thus there are no diffusional restrictions within the pores, leading to a higher Cr(VI) adsorption than that previously reported for similar systems. Chromium desorption for material reutilization was carried out in basic media. Results showed that the amino groups were grafted successfully without mesostructure damage. These groups are essential for the metal ion removal and no significant leaching was observed after four use/regeneration/use cycles. The batch equilibrium data fitted well the Langmuir isotherm with a maximum adsorption capacity of 87.1 mg g−1 at 25 °C. A discussion about the relationship between structure and its behavior as adsorbent, including regeneration and reusability, is given.

Comparison of different rice straw based adsorbents for chromium removal from aqueous solutions

Chromium is a well known highly toxic heavy metal and one of the major pollutants in the tannery wastewaters. This research aims at studying the feasibility of using different rice straw-based adsorbents, fine rice straw (FRS), rice straw carbon (RSC), and rice straw activated carbon (RSAC) for removal of chromium from aqueous solution. In batch experiments, effect of operating variables such as contact time, adsorbent dose, pH of solution, and initial chromium concentration have been studied. The best operating conditions were: FRS—equilibrium time 12 h, FRS dose 20 g/l, pH 2; RSC—equilibrium time 8 h, RSC dose 12 g/l, pH 2; RSAC—equilibrium time 4 h, RSAC dose 8 g/l, pH 2. The maximum adsorption achieved at pH 2.0 for all studied adsorbents. The adsorption results for the studied adsorbents were fitted to Langmuir and Freundlich isotherms with correlation coefficient of 0.99, 0.95, respectively, and the maximum adsorption capacity was 7.99, 18.83, and 40.32 mg/g. Desorption of chromium from different rice straw (RS) particles using acid and base treatment exhibited a higher desorption efficiency by more than 85, 95, and 97% for FRS, RSC, and RSAC, respectively. The present study showed that RS could be used as a biosorbent for removal of chromium from aqueous solution with a limited ratio.

Adsorption Desorption of Chromium (III) Ion on Cellulose from Wood Powder

This study of adsorption desorption of chromium ion on cellulose from wood powder has been carried out systematically and also wood powder was used as adsorbent control in this research. Adsorption process was studied through investigation of adsorption time and variation of chromium ion in the adsorption. Desorption process was investigated using several desorption reagents such as hydrochloric acid, ammonium acetate, sodium EDTA, and water. Data of adsorption time of chromium ion on cellulose and wood powder was calculated to obtain adsorption rate constant of chromium ion. Then the data of variation concentration of chromium was formulated to obtain adsorption capacity of chromium ion on cellulose and wood powder. The results showed that adsorption rate constant of chromium on cellulose is 0.007 min -1 and 0.002 min -1 for wood powder. Adsorption capacity of chromium ion on cellulose is higher than on wood powder while 76.92 mol/g for cellulose and 55.56 mol/g for wood powder. The results of desorption using various desorption shows sodium EDTA is appropriate reagent for desorption of chromium ion on both cellulose and wood powder. Keywords - adsorption, cellulose, chromium, desorption.