Film Diffusion Model Research Articles

Synthesis of a novel epibromohydrin modified crosslinked polyamine resin for highly efficient removal of methyl orange and eriochrome black T

Abstract A novel epibromohydrin modified crosslinked polyamine resin (EBPAR) was synthesized for highly efficient removal of Methyl orange (MO) and Eriochrome Black T (EBT) from aqueous solution. EBPAR has been characterized extensively by FTIR, XPS, TGA, XRD and FESEM methods. The resin can efficiently remove MO (> 99%) at pH range of 4–6 and EBT (> 97%) at pH 3. The experimental data of dyes adsorption onto resin was examined by a variety of adsorption models including pseudo-first and second order kinetic models, Langmuir, Temkin, Freundlich, Dubinin–Radushkevich, intra-particle diffusion and film diffusion models. Furthermore, the effect of pH, dosage, initial dye concentration and temperature on the adsorption was also investigated. Experimental results revealed that the adsorption of EBT is mainly controlled by film diffusion (xi = 14.5 mg g − 1) as compared to MO where intra-particle diffusion (R2 = 0.9995) is the rate limiting step. Adsorption interactions of dyes onto EBPAR were investigated using Field Emission Scanning Electron Microscope (FESEM) and X-ray diffraction (XRD) analysis.

Enhanced adsorption and removal of urea from aqueous solutions using eco-friendly iron phosphate nanoparticles

This work reports of using iron phosphate nanoparticles (nano-FePh) as adsorbent for removing urea. Hence, the adsorption of urea on nano-FePh was investigated as a function of reaction time, temperature, catalyst weight, shaking speed and solution pH. Amorphous iron phosphate is synthesized by a cost-effective method reflux. The nano-FePh is characterized by different techniques including; X-ray diffraction (XRD), transmission electron micrograph (TEM), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-Ray Spectroscopy (EDX), FT-IR and BET surface area determination. Highest adsorption extent obtained at pH range of 7–9 with uptake of urea equals to 1.2 × 102 mg/g (gram of nano-FePh). The reaction kinetics of the adsorption of urea follows a pseudo-first-order model. Application of homogenous film diffusion model and matrix diffusion model is carried out and analyzed. The model of the diffusion liquid film controls the process at the first adsorption step and then at the final stage is under control by matrix diffusion model. Frumkin adsorption isotherm is found to fit with the experimental data. The kinetics and thermodynamic parameters have been determined and analyzed. The nano-FePh adsorbent was stable and the adsorption capacity was remaining excellent after 10 cycles.

Absorption kinetics analysis for removal of fine particle from simulated flue gas by emulsion liquid membrane

In order to study the mechanism of fine particle removal from flue gas by emulsion liquid membrane (ELM), adsorption model was investigated. Three adsorption kinetics equations (first order, second order and third order) were applied to simulate the uptake of fine particle from flue gas by ELM. The results show that the experimental data was fitted better with the pseudo-second-order equation model than those with other equation models. In order to further study the diffusion mechanism, the intraparticle diffusion model and the liquid film diffusion model were employed to study the adsorption mechanisms of ELM. The result suggests that the two stage adsorptions happened for fine particle from flue gas by ELM and these steps accord with intraparticle diffusion models.

The study of adsorption efficiency of rice husk ash for removal of phenol from wastewater with low initial phenol concentration

This research work aimed to assess the adsorption efficiency of rice husk ash for removal of phenol from wastewater. The authors studied the morphology and characterization of rice husk ash using SEM, FTIR, XRD and BET analyzers and carried out the batch experiments to evaluate the removal percentage of phenol with variation of pH (3–11), adsorption time (30–270 min), adsorbent dose (0.5–4.0 gm/L), phenol concentration (5–20 mg/L) and temperature (25–35 °C). It was observed that the maximum removal reached as high as 95%. The testing of kinetic models showed that the second-order model was better than the first-order model. Elovich model showed that the adsorption process was chemical, Reichenberg model showed that adsorption occurred because of film diffusion, Furusawa and Smith model showed that phenol moved faster from bulk to solid stage, Boyd model indicated that the process supported chemisorptions, and Fick’s model implied that film and intraparticle diffusion took 45 min and 135 min, respectively. Testing of isotherm models indicated that Langmuir, Freundlich and Temkin models were all supportive of equilibrium data. The Dubinin–Radushkevich isotherm indicated that the process was explained by feeble physical adsorption. The isothermal study indicated that the process was random, endothermic and spontaneous. Although some studies had been done for removal of phenol using rice husk ash in the past, this research had covered the extensive works on the characterization of the adsorbent, extent of phenol removal with the variation of several process variables, and testing of several models in the areas of kinetics, isotherms, and thermodynamics. Further, the novelty of this research was that the experiments were carried out for treatment of wastewater exclusively with low initial phenol concentrations so that the results can be effectively applied in several small- and medium-scale industries at lesser costs, particularly in the Third World countries.

Textile wastewater treatment by agro-industrial waste: Equilibrium modelling, thermodynamics and mass transfer mechanisms of cationic dyes adsorption onto low-cost lignocellulosic adsorbent

Abstract The present paper aims to develop a low cost, efficient and environment-friendly process by the use of an agro-industrial waste to purify dye-contaminated aqueous solutions. The ability of palm-date stones to adsorb basic violet 3 (BV3) and basic red 2 (BR2) from wastewaters is assessed through kinetic, thermodynamic and equilibrium investigations. FTIR spectra indicated that hydroxyl and carbonyl groups are the possible functional groups involved on dyes uptake. Kinetic and dynamic studies showed that 77 and 93% of BR2 and BV3 were removed within a contact time of 15 min, which proves the applicability of the process at an industrial scale. Kinetic data were extracted using pseudo-first-order, pseudo-second-order, Elovich and Brouers–Sotolongo models. Calculations gave that the rate sorption was simultaneously controlled by film and intra-particle diffusion models, which was confirmed by Biot numbers. Using a non-linear regressive method, the equilibrium isotherm data were evaluated by six different three-parameter models which were compared to two-parameter isotherm models. Error analysis showed that Hill and Koble–Corrigan models best described the uptake of BR2, whereas Toth, Khan and Redlich–Peterson fit better BV3 removal. Thermodynamic study showed that, for both pollutants, the adsorption was endothermic, spontaneous, according physisorption mechanism and involving probably hydrogen bonds.

The Removal of Single and Binary Basic Dyes from Synthetic Wastewater Using Bentonite Clay Adsorbent

In order to broaden the application of Bentonite clay, an easily obtainable and bio-available low cost adsorbent, it was employed for the decolourization of synthetic wastewater consisting of single and binary basic dyes (Malachite green and Rhodamine b). The adsorbent was used as obtained without any further modification and also characterized for its specific surface area, point of zero charge and its surface functional groups pre and post dyes sorption was determined using Fourier Transform Infrared Spectroscopy (FTIR). Batch adsorption methods were employed in order to study the effects of pH, Ionic strength and contact time in the single solute system. The parameters of sorption of Rhodamine B (RDB) and Malachite green (MG) were obtained and fitted to three isotherm models; Freundlich, Langmuir and Temkin. The Freundlich plot analysis indicated the process occurred via heterogeneous coverage of adsorbent by both dyes. The kinetics of adsorption data were analyzed using the; pseudo-first order, pseudo-second order, Intraparticle diffusion, film diffusion, and Boyd kinetic models. Over the study of these parameters, the film diffusion mechanism was found to predominate in the sorption process of the dyes. Competitive sorption studies were carried out by using both dyes as either the adsorbate of interest or as the interfering specie. The competitive co-coefficient values obtained from interfering MG in RDB removal were significantly lower than those obtained from interfering RDB in MG removal, indicating that the presence of RDB in the aqua matrix had antagonistic effect on MG adsorption by Bentonite.

Adsorption studies of Cr(VI) and Cu(II) metal ions from aqueous solutions by synthesized Ag and Mg co-doped TiO2 nanoparticles

ABSTRACTThis communication provides the eliminating of heavy metals from water resources using Ag-Mg/TiO2 nanoparticles. The nanoparticles with a size of 15 nm were prepared using sol-gel technique and used for the removal of Cr(VI) and Cu(II) from waste waters. Batch sorption studies were carried out to investigate the adsorption of the above metal ions for a concentration range of 0.1–10 mg/L. The maximum sorption capacity values were found to be 2.42 mg/g for Cr(VI) and 2.03 mg/g for Cu(II) at a concentration of 0.1 ppm. The mechanism of adsorption was also investigated. The results showed that both Freundlich and Dubinin–Radushkevitch isotherms were found to be the best fit for the adsorption of metals. The results from kinetic data reveal that the pseudo-second-order and Reichenberg film diffusion models were found to be well fit for the experimental data. The value of the thermodynamic parameter ΔH° revealed the endothermic adsorption process and negative value of ΔG° shows the feasibility and spontaneity of material–anion interaction. In addition, the method is considered to be simple and cost-effective, and shows excellent adsorption removal properties on heavy metals for industrial applications.

Synthesis of magnetic iron‐manganese oxide coated graphene oxide and its application for adsorptive removal of basic dyes from aqueous solution: Isotherm, kinetics, and thermodynamic studies

Adsorptive removal of cationic dyes such as methyl violet (MV) and methyl green (MG) from aqueous solution using magnetic iron‐manganese oxide coated graphene oxide (IMGO) was examined. The IMGO was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X‐ray spectroscopy, X‐ray diffraction (XRD), N2 adsorption–desorption isotherm, and vibrating sample magnetometer. The effect of different process parameters such as contact time, IMGO dose, initial dyes concentration, initial solutions pH, and temperature was investigated. The equilibrium experimental data were fitted with Langmuir, Freundlich, Dubinin–Radushkevich (D‐R), and Temkin isotherm models. The data fitted well with Freundlich isotherm model suggesting multilayer adsorption of dyes onto heterogeneous adsorbent surface. The Langmuir adsorption capacity (Qm, mg/g) of IMGO with MV and MG was 172.96 and 195.64, respectively. The data obeyed the pseudo‐second order kinetic model, and the mechanism of adsorption was controlled by both intra‐particle and liquid film diffusion models. The adsorption process was found to be spontaneous, endothermic, and physical in nature. The dye‐loaded IMGO was regenerated and used for at least four cycles without any substantial loss of its efficacy. The present adsorptive removal studies of MV and MG revealed that IMGO is an effective and efficient adsorbent for the removal of basic dyes from aquatic system. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S214–S229, 2019

Smart construction of mesoporous carbon templated hierarchical Mg-Al and Ni-Al layered double hydroxides for remarkably enhanced U(VI) management

Designing and fabricating environmental friendly adsorbents with more accessible active sites and higher specific surface area for achieving rapid kinetics and high efficiency have become an impending challenge in radionuclides’ pollution remediation. To overcome these issues, we rationally designed the hierarchical structured layered double hydroxides with mesoporous carbon template (CMK-3@LDHs) by in situ hydrothermal method. The adsorption data could be well simulated with pseudo-second-order and Langmuir model, and the results indicated that the CMK-3@LDHs exhibited higher adsorption capacities (171 mg·g−1 for CMK-3@Mg-Al LDHs and 301 mg·g−1 for CMK-3@Ni-Al LDHs at pH = 5.0) and more rapid kinetics (achieved equilibrium within 30 min) than SBA-15@LDHs towards U(VI). The kinetic model simulation demonstrated that the adsorption rate was dominated by intra-particle and film diffusion models simultaneously. In addition, the interaction between U(VI) and LDHs was pH-dependent and weakly related with ionic strength at pH < 5, suggesting that the process was mainly driven by the combined mechanism of electrostatic interaction and inner-sphere surface complexation. The characterization indicated that U(VI) removal was predominately controlled by isomorphic substitution and complexation with surface hydroxyl groups. In the further simulation experiments, the CMK-3@LDHs exhibited relative high adsorption efficiency in many water systems even in seawater, which confirmed the potential application of CMK-3@LDHs in efficient extraction and remediation of radionuclides from different kinds of wastewater systems.

Adsorption of trace Iron from nickel sulfate solutions using Monophos resin

This paper deals with the removal of trace iron from nickel sulfate solution using Monophos resin. Kinetics, thermodynamics and adsorption mechanism of iron adsorption were studied. Kinetic and thermodynamic parameters as well as equilibrium constants were calculated based on various equilibrium models. Liquid film diffusion, particle diffusion and chemical reaction models were used to fit the experimental data. It was shown that the adsorption mechanism was well represented by particle diffusion model. And pseudo-second-order and intra-particle diffusion model were more consistent with the adsorption process and clearly predicted the intra-particle distribution of iron concentration. Langmuir isotherm well described the adsorption data. Thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic. An iron adsorption rate of 89% was reached with iron concentration being reduced from 1.92 mg/L to 0.21 mg/L.

Isotherm and kinetic modelling of Toluidine Blue (TB) removal from aqueous solution using Lemna minor

ABSTRACTThe aim of this study was to investigate the ability of Lemna minor for Toluidine Blue (TB) removal. Influence of the initial concentration over the removal process was considered. Experimental data have been analyzed using Langmuir, Freundlich, Dubinin–Radushkevich (D–R), and Elovich isotherm models. In addition, several kinetic models, pseudo-first-, pseudo-second-order, intraparticle and film diffusion models were considered. Langmuir and Freundlich isotherm suggested a favorable adsorption of TB by Lemna minor plants. From the D–R the mean free energy was calculated to be 11.18 kJ/mol, which indicates that TB adsorption was characterized by a chemisorption process. Kinetic studies showed that liquid film diffusion plays an important role during the process. Adsorption capacities of up to 26.69 mg/g and a high capacity of adaptation indicated that phytoremediation using Lemna minor could be a valuable alternative for dyes removal from wastewaters.

CO2-spherical activated carbon as a new adsorbent for Methylene Blue removal: Kinetic, equilibrium and thermodynamic studies

In this study, the efficient adsorption of methylene blue (MB) onto spherical activated carbon (SAC) prepared from the sucrose hydrothermally carbonized and physically activated with CO2 is reported for the first time. The obtained SAC surface exhibited acidic features, according to Boehm titration (1.00 mmol g−1 of acid groups) and the pHPZC (3.18). The optimum pH for MB adsorption onto SAC was of 7.0. Adsorption studies showed that kinetic data followed the pseudo-second-order and Elovich models, whereas the intraparticle diffusion and film diffusion models were tested and the results revealed that the rate-limiting step of adsorption process was not only the intraparticle diffusion. Equilibrium adsorption studies were best described by Dubinin-Radushkevich, Sips and Langmuir isotherm models, with a maximum monolayer adsorption of 211.3 mg g−1. Thermodynamic results showed negative values of Gibbs free energy change (ΔG°) and positive values of enthalpy (ΔH° = 3.13 kJ mol−1) and entropy change (ΔS° = 66.20 J mol−1 K−1), indicating that MB adsorption onto SAC is spontaneous and endothermic.

Adsorptive Separation of Fructose and Glucose by Metal–Organic Frameworks: Equilibrium, Kinetic, Thermodynamic, and Adsorption Mechanism Studies

In this work, seven metal–organic frameworks [ZIF-8, MIL-53(Cr), MIL-96(Al), MIL-100(Cr), MIL-100(Fe), MIL-101(Cr), and UiO-66 ] were applied for adsorptive separation of fructose–glucose mixture. UiO-66 exhibited better performance in adsorption capacity and selective adsorption of fructose. The adsorptive process with UiO-66 was further investigated in detail including kinetic, isotherm, and adsorption mechanisms. The rate-determining step analysis based on film diffusion and intraparticle diffusion model suggested that the adsorption process was controlled by multiple steps, which fitted the pseudo-second-order model. The Freundlich model was fitting better than the Langmuir model, which indicated multilayer adsorption on heterogeneous surface. The thermodynamic parameters (ΔG, ΔH, and ΔS) were calculated, indicating that adsorption process on UiO-66 was an endothermic and entropy increment process. UiO-66 can be a promising adsorbent for adsorptive separation of fructose and glucose.

Equilibrium and kinetics modeling of fluoride adsorption onto activated alumina, alum and brick powder

For the present study three adsorbents namely, activated alumina, alum and brick powder has been studied and tested for its fluoride removal efficiency by kinetics and equilibrium models at varying dose and initial fluoride conc. The experimental values were modeled for different adsorption isotherm and kinetic models. Equilibrium studies suggests that even though a high coefficients of correlation obtained using Langmuir-1 and Langmuir-5 expressions, the model does not describe perfectly the equilibrium data because of the higher calculated error values. Elovich isotherm exhibited very poor coefficients of correlation, lower than those obtained for Langmuir and Freundlich equation, which nullifies the assumption of the exponential covering of adsorption sites that implies multilayer adsorption in the studied concentration range. Freundlich model suggests that, activated alumina and alum are good adsorbent for fluoride adsorption (1.380 ≤ n ≤ 2.992), but brick powder can proved to be a good adsorbent only at lower fluoride conc. as suggested by n < 1 for F− conc. of 5 mg/L. Error analysis suggests good agreement between the experimental and predicted values, suggesting Freundlich model for the experimental equilibrium data. Comparing pseudo-first, -second and Elovich models, it was observed that fluoride adsorption was best represented by pseudo-second order model. Liquid film diffusion model analysis suggests that, as the straight lines did not pass through the origin, resistance or film diffusion might not be the sole rate-limiting step. The adsorption kinetics might be controlled by both film diffusion as well as intra-particle diffusion simultaneously.

Attenuation Kinetics and Desorption Performance of artocarpus altilis Seed Husk for Co (II), Pb (II) and Zn (II) Ions

The potential of Bread Fruit (artocarpus altilis)Seed Husk (BFSH) as low-cost biosorbent for the removal of Pb (II), Zn (II) and Co (II) ions from aqueous solution was investigated. The adsorbent was characterized by the Fourier Transform InfraRed (FT-IR)spectroscopy, Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). The batch methodology was utilized to determine the effect of pH, metal ion concentration, adsorbent dose, contact time and temperature on biosorption. Data generated were fitted into appropriate isotherm, kinetic and thermodynamic models. The effect of pH showed an increase in adsorption of metals with an increase in pH and an optimum pH of 5.0 was obtained for Pb (II), while 6.0 were obtained for Co (II) and Zn (II) ions biosorption. An equilibrium sorption contact time of 30, 40 and 60 min was obtained for Co (II), Zn (II) and Pb (II) ions respectively. The biosorption of metal ions was in the order Co (II) > Pb (II) > Zn (II). In general, the Freundlich model provided a better fit than the Langmuir, Tempkin, and Dubinin-Radushkevich isotherm models with R2 values greater than 0.9. The pseudo-first-order kinetic model was applicable in the adsorption of Pb (II) and Zn (II) ions while the pseudo-second-order model provided the best fit for Co (II) ion adsorption. The adsorption mechanism was found to be controlled by the liquid film diffusion model (R2>0.9) rather than the intraparticle diffusion model (R2<0.9). Thermodynamics revealed a spontaneous, feasible, exothermic physisorption process and over 60% of the metal ions were desorbed using 0.1M HCl and 0.1M NaOH as eluent. The results showed that BFSH could be utilized as low cost adsorbent for the removal of toxic heavy metals from solution.

Poly(AA-co-VPA) hydrogel cross-linked with N-maleyl chitosan as dye adsorbent: Isotherms, kinetics and thermodynamic investigation

In this study, hydrogel polymer was synthesized by incorporation of acrylic acid (AA), vinylphosphonic acid (VPA) and N-maleyl chitosan which was prepared through the acylation reaction between maleic anhydride and chitosan. N-maleyl chitosan crosslinked P(AA-co-VPA) hydrogel was utilized for the effective adsorption of crystal violet (CV) and methylene blue (MB) dyes from aqueous solutions. The synthesized hydrogel was characterized by using FTIR, SEM, EDS, TGA-DTA, and DSC methods. The effecting parameters on adsorption of dyes such as initial concentration of dyes, temperature, pH and adsorbent polymer dose were studied. The adsorption isotherm was analyzed in different temperature using Langmuir, Freundlich, Temkin and Redlich-Peterson models and the adsorption data were well described by Redlich-Peterson isotherm model. The adsorption kinetics was analyzed using pseudo first-order, pseudo second-order, intraparticle and film diffusion models in 20, 30, 40 and 50 mg/L of dye solutions and the adsorption data were well described by pseudo-second-order model. The maximum adsorption capacity of the hydrogel polymer for removal of CV and MB in 50 mg/L of dye solutions was 64.56 mg/g and 66.89 mg/g, respectively. Thermodynamic studies recommended that the adsorption process was endothermic and spontaneous. Furthermore, the adsorbent was successfully employed for successive four cycles of adsorption-desorption.

Adsorptive removal of Congo red from aqueous solution using zeolitic imidazolate framework–67

In the present paper, the Congo red dye (CGR) adsorption onto zeolitic imidazolate framework–67 (ZIF–67) is demonstrated. ZIF–67 was synthesized using the microwave method. The obtained ZIF–67 was characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), thermal gravity analysis (TG), and X-ray photoelectron spectroscopy (XPS). ZIF–67 was employed to adsorb CGR from aqueous solutions. The first-order and second-order kinetic model, and Weber’s intra-particle-diffusion and Boyd’s film-diffusion model were utilized to study the adsorption kinetics. The equilibrium adsorption data at different temperatures were interpreted using the Langmuir and Freundlich models. The thermodynamics from 301 K to 331 K was also addressed. ZIF–67 exhibited excellent adsorption in terms of favourable thermodynamics, ultra-high adsorption and superb fast kinetics. The adsorption capacity of ZIF–67 for CGR could be as high as 714.3 mg g−1 at 301 K, which could be improved at higher temperatures. In addition, ZIF–67 also exhibited very high adsorption for some other dyes such as rhodamine B and methylene blue. ZIF–67 was stable and could also be conveniently reused for several times. These peculiarities facilitate ZIF–67 to become one of the most promising adsorbents to remove dyes from water.

Hierarchical porous membrane via electrospinning PIM-1 for micropollutants removal

Ideal adsorbents are featured by both high adsorption capacity and high adsorption rate. Current adsorptive membranes enjoy good mass transfer performance but have limited sorption capacity. Microporous organic polymer has superiorities of small pore size and high surface area which is conductive to high adsorption capacity, but usually suffers from high mass transfer resistance. In this work, the polymer of intrinsic microporosity PIM-1 was fabricated into microfiber membranes by electrospinning for carbendazim and phenol adsorption. The PIM-1 and its electrospun membranes were characterized by 1H NMR, GPC, ATR-FTIR, FESEM, TG and BET measurements. The electrospun PIM-1 membrane was demonstrated to have hierarchical porous structure with high surface area. The equilibrium adsorption capacity for carbendazim and phenol was 0.084 mmol/g and 0.804 mmol/g, respectively. The adsorption isotherm fits well with Langmuir model and the adsorption kinetic can be described by film diffusion and chemical reaction model. The membrane can retain 95% of its initial capacity after cycling 10 times. Both the sorption capacity and kinetic coefficients are high when comparing with other sorbents for either carbendazim or phenol, demonstrating that the electrospun PIM-1 is a good adsorbent.

Process Design Aspects for Scandium-Selective Leaching of Bauxite Residue with Sulfuric Acid

Aiming at the industrial scale development of a Scandium (Sc)-selective leaching process of Bauxite Residue (BR), a set of process design aspects has been investigated. The interpretation of experimental data for Sc leaching yield, with sulfuric acid as the leaching solvent, has shown significant impact from acid feed concentration, mixing time, liquid to solids ratio (L/S), and number of cycles of leachate re-usage onto fresh BR. The thin film diffusion model, as the fundamental theory for leaching, either with constant particle size for selective leaching, or with shrinking particle size for less- or non-selective leaching, interprets the relevant experimental data. In both cases, a concept for an unyielding core supplements the basic model. Especially for the selective leaching mild conditions, the simplest model version agrees with the experiments, since both prove 1st order kinetics, while for extreme conditions, a combined conversion rate model with diffusion and chemical reaction inside particles is proposed. The maximization of Sc recovery per unit of consumed solvent emerged as highly critical for the process economics.

REMOVAL OF HEXAVALENT CHROMIUM USING TWO INNOVATIVE ADSORBENTS

Hexavalent chromium Cr(VI), a constituent of wastewater from many industries, is regulated by the Environmental Protection Agency (EPA) as one of the priority pollutants. Adsorption is an important technique that can be used for Cr(VI) removal from wastewater. The challenge in adsorption techniques is to find a cheap, widely available adsorbent that has a high adsorption capacity to Cr(VI). Dates stones (DS) and palm fiber (PF) are two agricultural wastes that are produced from palm trees. These adsorbent materials were tested in batch systems to investigate the different factors that may affect the adsorption process, e.g. adsorbent dose, initial adsorbate concentration, pH of aqueous solution and agitation time. Equilibrium models tested include Langmuir, Freundlich, Temkin and Dubinin-Radushkevich. Freundlich adsorption isotherm was found to best fit the experimental data. The maximum adsorption capacities obtained for DS and PF were 16 and 6 mg/g, respectively. Kinetic studies indicated that the adsorption of Cr(VI) on both DS and PF was fast in the first stage of the adsorption process. The equilibrium was reached in less than 2 h for both adsorption systems. The adsorption process was found to be second order with both adsorbent and adsorbate concentration to affect the adsorption process. Film diffusion and intraparticle diffusion models were found to simultaneously influence the adsorption. The adsorption process was found to be favorable and of physical nature.