Equilibrium Adsorption Data Research Articles

Kinetics and thermodynamics of Isolan Bordeaux 2S-B dye adsorption on chemically synthesized graphene particles

Dyes in wastewater are highly toxic pollutants that have negative physical, chemical, and ecological effects on aquatic ecosystems even at low concentrations. In this study, the efficiency of chemically synthesized graphene oxide (CG) for the removal of the organic dye Isolan Bordeaux 2S-B and the principles of adsorption were investigated. Scanning electron microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) analyses were performed to characterize the CG, and the point of zero charge value was determined. The optimal conditions were found to be a pH of 2, an adsorbent dosage of 0.2 g, and a reaction time and temperature of 30 min and 25 °C, respectively. The adsorption equilibrium data fitted well with the Langmuir isotherm (R2 =0.98, RMSE = 0.38). The adsorption kinetics data followed a pseudo-second-order kinetic model (R2 = 0.99). Thermodynamic studies have shown that adsorption is exothermic and spontaneous. Desorption-regeneration studies demonstrated that CG is a highly stable adsorbent, and experiments in the presence of foreign ions show that it has a high selective affinity for anionic dyes. CG is effective not only in removing IB 2S-B but also shows promise in selectively removing anionic dyes from wastewater as a long-lasting adsorbent.

Hyperbranched-Polyethylenimine-Functionalized Coal Fly Ash as an Adsorbent for the Removal of Hexavalent Chromium and Reuse as a Dye Photocatalyst.

Coal fly ash (CFA) has been extensively researched as an adsorbent for heavy metals, but its application is limited by its low adsorption capacity. The modification of CFA with hyperbranched polymers results in improved adsorption capacities. Hyperbranched polyethylenimine (HPEI) is a hyperbranched polymer containing NH2 groups that can bind with heavy metal ions through complexation or electrostatic interactions. In this study, CFA-HPEI adsorbents with various HPEI loadings (1-5%) were prepared and evaluated for the removal of Cr(VI). The successful incorporation of HPEI onto CFA was confirmed using Fourier transform infrared, elemental analysis, and X-ray photoelectron spectroscopy (XPS). The 3% CFA-HPEI loaded adsorbent resulted in optimum results when the effect of pH and adsorbent dosage was studied. The pseudo-second-order kinetics model best described the adsorption kinetics at an initial concentration of 20 mg/L. The Freundlich adsorption isotherm model best fitted the equilibrium adsorption data with a maximum adsorption capacity of 85.93 mg/g. The Cr-loaded adsorbent was reused as a photocatalyst to degrade methylene blue (MB) in the presence of visible light. The loaded adsorbent degraded 98.9% of MB (5 mg/L) within 180 min and was accompanied by compounds with m/z of 173 and 234, corresponding to the intermediate degradation of Azure A. The XPS analysis confirmed the coexistence of Cr(III) and Cr(VI) on the surface of the adsorbent. In addition, the loaded adsorbent exhibited good stability following MB degradation with no structural changes observed. Thus, CFA-HPEI adsorbents can be utilized as low-cost adsorbents for the remediation of toxic Cr(VI) from water and wastewater. The Cr-loaded CFA-HPEI adsorbent can be effectively reused as a photocatalyst, thus reducing environmental pollution.

Adsorption of methyl ester sulfonate surfactant on Berea sandstone: Parametric optimization, kinetics, isotherm and thermodynamics studies

Anionic surfactants are utilized as an enhanced oil recovery (EOR) additive in sandstone reservoirs due to their excellent surface-activity and self-assembly behaviour. Considering the toxicity of some of the conventional surfactants and the clamour for sustainability approach for oil and gas operations, this present study focuses on application of anionic bio-based surfactant (methyl ester sulfonate, MES) synthesized from used cooking oil in EOR. Studies on MES adsorption onto sandstone reservoir rock were conducted, and the influence of static conditions on adsorption rate using Taguchi experimental design approach was explored. Adsorption data were analyzed using various isotherm and kinetics models. The obtained findings from optimization studies showed that salinity had a significant effect on the process, followed by temperature and pH. The concentration of surfactant had the least effect on the static adsorption process. At an optimum initial MES concentration of 500 ppm, salinity of 3.0 wt%, pH of 4.0, and temperature of 30 °C, the maximum extent of MES adsorbed by the sandstone was 98.9±0.69%. Langmuir isotherm and pseudo-second-order kinetics models were found to fit well with the adsorption equilibrium and kinetics data, respectively. The obtained values of thermodynamic parameters confirmed that MES adsorption onto sandstone was feasible, spontaneous, and exothermic.

Rapid and effective antibiotics elimination from water by Fe-BTB MOF: An insight into adsorption mechanism

Tetracycline (TC) and sulfamethoxazole (SMZ) are common antibiotics utilized in human and veterinary medicines to overcome bacterial infections. However, due to their poor metabolism, they can easily be excreted into wastewater or sewage, leading to bioaccumulation and posing a risk to the local environment. This research studied the removal of SMZ and TC using a novel Fe-BTB MOF. The results showed that the Fe-BTB MOF achieved excellent adsorption capacities of 649 and 276 mg g−1 for SMZ and TC, respectively, within 1 h. The kinetics and equilibrium adsorption data correlated well with the pseudo-second-order and Sips models, respectively, suggesting favourable chemical adsorption for SMZ and TC over the MOF. Adsorption experiments, spectroscopic findings, and theoretical calculations suggest that π-π stacking, electrostatic, and hydrogen bond interactions played the main role in the adsorption mechanism. Fe-BTB regeneration was satisfactory for its use in treating antibiotic-contaminated wastewater, allowing its reuse for at least four cycles. Furthermore, water samples from different sources (tap, streams, sea, lake) were also used to confirm the excellent adsorptive performance of this Fe-BTB MOF in practical application.

Synthesis and characterization of the magnetic chitosan/zinc oxide nanocomposite: an efficient magnetic adsorbent for removal of harmful aromatic micropollutants from wastewater

In this work, a magnetic chitosan/zinc oxide nanocomposite (CS/ZnO-Fe3O4) was fabricated for efficient adsorptive removal of harmful aromatic micropollutants, including Cephalexin (CFX) antibiotic and Eosin B (EB) dye from wastewater samples. To maximize the adsorption efficiency of the CS/ZnO-Fe3O4, the adsorption process was first modeled and statistically optimized by using the response surface methodology based on central composite design (RSM-CCD). The results demonstrated that the maximum removal efficiency of the adsorbent for CFX and EB was 98.87% and 99.08%, respectively. Also, the adsorption isotherms, kinetics, and thermodynamics were also studied in detail under the optimum conditions. The results indicated that the adsorption equilibrium data was fit well with the Langmuir isotherm model, which indicated monolayer adsorption via chemisorption process. The Langmuir maximum adsorption capacity (Qmax) was 81.38 mg g−1 and 144.4 mg g−1 for CFX and EB, respectively. The adsorption kinetic was followed by the pseudo-second-order kinetic model, and the thermodynamic studies showed that the adsorption process was endothermic and spontaneous, as well as that adsorption entropy was also increased during the process. Also, the main adsorption mechanism was considered to be based on H-bonding, n-π, and electrostatic interactions. The regeneration experiments indicated that the spent adsorbent was easily regenerated by NaOH solution (0.1 mol L−1) and reused for subsequent cycles without a significant decrease in its performance, so that removal efficiency remained about 90% at the fourth cycle. Overall, the results indicated that CS/ZnO-Fe3O4 could be used as a promising adsorbent for the efficient removal of aromatic micropollutants from wastewater.

Optimization of adsorption conditions for Acid Chrome Blue K removal from aqueous solution using sugar-based activated carbon: Equilibrium isotherms and kinetics modeling

In this study, white sugar was dehydrated and then activated, producing extremely porous carbon as a result. The activated sugar-based carbon (ASC) was prepared by first dehydrating white sugar to produce dehydrated sugar carbon (DSC) which was then chemically activated in a nitrogen atmosphere using NaOH as activating agent. With the aid of central composite design (CCD), a component of response surface methodology (RSM), the ideal circumstances for the removal of Acid Chrome Blue K (ACBK) dye onto the ASC adsorbent from aqueous solution were investigated. Adsorbent dosage of 0.60 g, initial concentration of 79 mg/L and shaking speed of 258 rpm were the ideal adsorption conditions attained. The obtained experimental and predicted values were 94.89% and 94.22%, respectively, demonstrating good agreement between the experimental and predicted values from the model with only a modest error of 0.71. The linearized Langmuir equations in five different versions, as well as the Freundlich and Temkin adsorption isotherms, were used to simulate the adsorption data. Chi square (χ2) and the correlation coefficient (R2) were taken into consideration while assessing the validity of each isotherm model to support the selection of the best adsorption model. The equilibrium adsorption data were best represented by the order Langmuir-2 > Freundlich > Temkin isotherms. The outcomes showed that the best model for describing the kinetics data was pseudo-second-order.

Evaluation of aqueous phase adsorption of Acid Brown on mesoporous activated carbon prepared from Azolla Pinnate seaweed

<p>A mesoporous activated carbon was produced from the Azolla Pinnate (AP) seaweed by two-step chemical activation technique using sulphuric acid as activating agent. The adsorption of Acid Brown (AB) from aqueous solutions is examined using the produced carbon (AP). The produced activated carbon renders a homogeneous porous structure, predominantly mesoporous with 686.5 m2/g of BET surface area. The infra-red spectrum revealed AB affinity by multiple functional groups. The point of zero charge and the pH studies evidenced that the surface charge responsible for electronic affinity favours adsorption at higher pH. The SEM and FTIR analysis of AP before and after adsorption of acid brown shows multiple interactions, which is further substantiated by equilibrium, kinetic and thermodynamic models. Equilibrium adsorption data matched best with Langmuir isotherm model, thus primarily follows chemical interaction. However, physical affinity and heterogeneity of surface and species interaction also do exist nearly equally. Pseudo-second order kinetics provided the best explanation of the adsorption kinetics. The temperature variation studies revealed that acid brown adsorption is endothermic with high surface affinity.</p>

Activated carbon from sugarcane bagasse as support for lipase immobilization by physical adsorption technique

Lipases are recognized as the most important group of catalysts in biotechnology. However, utilization of free enzymes is often hampered by the need for more operational stability, high cost, and non-reusability. Most of these obstacles can be solved by lipase immobilization. This work's objective was to evaluate the performance of the activated carbon obtained from sugarcane straw (SAC) as a support for lipase immobilization. Two lipases were immobilized by physical adsorption on SAC: Aspergillus niger 11T53A14 lipase and CalB (lipase B from Candida antarctica, Novozymes). Results revealed that the lipase had been anchored on the activated carbon with the lipase binding efficiency of 89 % (A. niger lipase) and 100 % (CalB) at the optimum experimental conditions (initial protein concentration 0.1 mg mL-1, 0.15 g of SAC, 25 °C, and 120 min). Langmuir isotherm fitted the adsorption equilibrium data of the lipases on SAC. SAC presents a high surface area and protein adsorption capacity. These results show that activated carbon synthesized from the sugarcane straw is a promising support for enzyme immobilization.

Adsorption Removal of Azo Dye (Methylene Blue) From Wastewater Using Biomaterials with Kinetic Modeling

Industrial wastewater containing dyes poses a significant environmental threat due to their persistence and potential toxicity. Adsorption using bio-based materials offers a promising and sustainable approach for dye removal. This study investigates the effectiveness of bio-based adsorbents derived from coconut husk, banana peels, and orange peels (pretreated with formaldehyde and sulfuric acid) for methylene blue (MB) removal. The adsorbents were characterized using SEM and FTIR. Batch adsorption experiments were conducted to evaluate the MB removal efficiency under various conditions (pH, dosage, temperature, agitation, and contact time). The results showed that the Freundlich isotherm model best described the equilibrium adsorption data, indicating favorable multilayer adsorption. Kinetic studies revealed a pseudo-first-order reaction with an exceptional removal efficiency of 99.94%. Notably, the R-squared value of 0.99992 signifies an excellent fit of the model to the experimental data. These findings demonstrate the remarkable potential of bio-based materials for MB removal from wastewater. This approach offers an eco-friendly and cost-effective solution for dye remediation in the textile and dyeing industries, contributing to cleaner water resources.

Synthesized polyetheretherketone/polyvinylalcohol nanocomposite modified with zinc oxide nanoparticles: As an effective adsorbent for removal of arsenic (III) ion from wastewater

The applicability of Polyetheretherketone/Polyvinylalcohol nanocomposite modified with zinc oxide nanoparticles synthesis for the removal of arsenic (III) ion from wastewater. Identical techniques, including BET, FT-IR, pHzero, and SEM, have to characterize this unknown material. The investigation shows the applicability of adsorbent PEEK/PVA/ZnONPs, as an available, suitable, and low-cost adsorbent for properly removing of the arsenic (III) ion from wastewater. The impacts of variables, including arsenic (III) ion concentration, adsorbent, pH, and time (30 mgL−1, 50.0 mg, 7.0, and 60.0 min). The adsorption equilibrium and kinetic data were fitted with the Freundlich isotherm model, and pseudo-second-order kinetics (R2: 0.997), with the maximum adsorption capacity of the arsenic (III) ion for adsorbent PEEK/PVA/ZnONPs (35.5 mgg−1), respectively. Thermodynamic parameters (ΔG°: −121.06 kJ/mol, ΔH°: −42.17 kJ/mol, ΔS°: −138.38 kJ/mol K−1), also indicated arsenic (III) ion adsorption as feasible, spontaneous and exothermic. To evaluate the practical applicability of the prepared adsorbent for the removal of As (III) ion from wastewater (containing humic acid, and other ions), it was subjected to sorption experiments. The results indicated that novel sorbent showed great potential as an affordable and efficient adsorbent for treating wastewater.

REMOVAL OF IBUPROFEN FROM WATER USING MAGNETIC Fe3O4-Ag2O/CELLULOSE AS AN ADSORBENT

Ibuprofen is widely used to reduce minor aches and fevers from a various condition such as the common flu. The increase in the waste of ibuprofen may cause contamination and raise a serious problem in the water effluence. It is needed to reduce the waste of ibuprofen by the adsorption process. Both cellulose from empty fruit bunch and modified bimetal oxides Fe3O4-Ag2O were synthesized and characterized as magnetic Fe3O4-Ag2O/cellulose adsorbent. The BET surface area was 177.7 m2 /g with a predominantly mesoporous structure. SEM EDX spectra proved an unsmooth adsorbent with irregular-sized particles. FTIR spectra at 552-693 nm are assigned to Fe-O and Ag-O stretching vibration. XRD pattern analysis shows the crystallized size is 34.16 nm. The highest removal efficiency of ibuprofen was obtained at acidic conditions (pH = 2), a concentration of 200 ppm, and a contact time of 120 min. The equilibrium adsorption data proved that the Freundlich isotherm is more favorable than the Langmuir isotherm model. The kinetic model showed that the pseudo-first-order is a more suitable model than the second-pseudo-order. The result of the experimental data proved that the Fe3O4-Ag2O/cellulose will be a potential adsorbent for ibuprofen removal.

Adsorption of acid red 18 from aqueous solutions by GO-COFe2O4: Adsorption kinetic and isotherms, adsorption mechanism and adsorbent regeneration

In the present study, graphene oxide-cobalt ferrite (GO-CoFe2O4) was synthesized by sol-gel method as an adsorbent in the removal of acid red 18 (AR18) dye. The characteristics of the magnetic adsorbent were analyzed through SEM, TEM, XRD, FTIR, N2 adsorption-desorption, and VSM. The findings of the diagnostic analysis showed a surface area of 58.92 m2/g, a pore size of 2 nm, and a magnetic property of 3.82 emu/g for the GO-CoFe2O4 composite. The effect of the operational parameters determined the maximum removal efficiency (100%) at pH of 5, adsorbent dosage of 1 g/L, and AR18 concentration of 25 mg/L. The effect of anions on the removal rate of AR18 by GO-CoFe2O4 composite was evaluated, and the results were its negative effect in reducing the efficiency in the order of NaCl < NaNO3 < Na2SO4 < Na2CO3. Thermodynamic parameters including ΔG°, ΔH°, and ΔS° explained that the adsorption of AR18 on the synthesized composite is favorable, spontaneous, and endothermic. The experimental data was studied by four kinetic equations including pseudo-first-order, pseudo-second-order, Elovich and intraparticle-diffusion and the results based on R2 and qe were consistent with pseudo-second-order kinetics. Eleven isotherm models were selected for adsorption equilibrium data, and the data were fitted with all isotherm models with R2 > 0.95. The results of adsorbent regeneration by peroxymonosulfate (PMS) activation showed that with increasing treatment time and PMS amount (up to 10 mM), the regeneration efficiency increases significantly up to 73.72%.

Activated carbon from Camellia oleifera shells for adsorption of Y(iii): experimental and DFT studies.

Yttrium is an important rare earth element and is widely used in fields such as special glass preparation, metallurgy, and materials science. However, it is difficult to recover yttrium ion waste from dilute solutions with traditional processes, resulting in a significant waste of rare earth resources. The simple, effective, and easy-to-operate adsorption method is the most promising method for recovering yttrium, which is of great significance for sustainable development of the rare earth industry. In this study, activated carbon was prepared from Camellia oleifera fruit shells (COS) using phosphoric acid activation, and efficient recovery of Y(iii) from the Camellia oleifera fruit shell activated carbon was studied. Adsorption equilibrium data showed that this activated carbon had a Y(iii) adsorption capacity of 35.41 mg g-1, indicating significant potential for recovery of yttrium ions. The adsorption of Y(iii) by the activated carbon prepared from COS was consistent with the Langmuir model, and the adsorption data were consistent with the pseudo second-order kinetic model, indicating that the adsorption process was primarily chemical adsorption. After adsorption, the surface of the activated carbon contained large amounts of N, O, and Y, indicating that Y(iii) was stably adsorbed. The mechanisms for adsorption of Y(iii) on three types of activated carbon were studied through DFT calculations. The results showed that Y(iii) interacted with the carbon atoms on the surfaces to form new chemical bonds. The yttrium ion adsorption capacities for the three different activated carbons decreased in the order C I > C II > C.

Zn-Al layered double hydroxide nanoparticles for efficient removal of food dyes from wastewater

The ability of layered double hydroxides clay (LDH) produced from ZnAl-NO3 to remove Sunset Yellow FCF (E110), Azorubine (E122), Tartrazine (E102), and Brilliant Blue FCF (E133) from an aqueous solution was studied. The effects of various variables on adsorption were studied. The obtained results show that the adsorption of various food dyes depends on the initial concentration, dose, pH, contact time, and temperature. The adsorption capacities at an equilibrium time of 40 min for E133, E122, E110, and E102 were 18.21, 21.46, 13.19, and 20.58 mg/g, respectively. The adsorption equilibrium data for aqueous solutions were analyzed using Langmuir and Freundlich isotherms and a thermodynamic study. Adsorption kinetics data for aqueous solutions was studied using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. The morphology for Zn-Al LDH was investigated by scanning electron microscopy (SEM) and BET (pore size = 0.004 cc/g). Equilibrium data were studied by Freundlich, Langmuir, and Temkin isotherms. As for thermodynamics, the value of ∆H° is negative, which means that the adsorption method is exothermic at a temperature range of 288–338 K. ∆S ° is a negative value indicating that the randomness is low, ∆G° is also negative means that the reaction is spontaneous. The FTIR spectroscopic analysis of LDH before and after the adsorption also confirms that the adsorption of food dyes was smooth and spontaneous on Zn-Al LDH providing an excellent and easy-to-use adsorption method for industrial application of wastewater treatment.

Study of methane upgrading using an activated carbon 3D-printed adsorbent

Although Maxsorb is a commercially available powder-form material, to be used in adsorption-based processes, its handling is easier if used with a structured geometry. Indeed, in the monolithic form, activated carbons have shown the potential to be used in adsorption-based applications. The use of additive manufacturing (AM) allows the development of structured adsorbents with adaptable geometries. In this work, Maxsorb activated carbon was 3D-printed into a monolithic structure using a polymeric binding agent, carboxymethylcellulose (CMC). The monolith was obtained through direct writing of filaments of an ink containing the adsorbent and the binding agent in a layered way, according to a pre-established pattern. The material was comprehensively characterized by N2 physisorption at 77 K and CO2 adsorption at 273 K to analyze the porous structure, SEM, and mercury porosimetry to evaluate the macrostructure porosity. To examine the affinity of CH4 and N2 with the adsorbent, pure adsorption equilibrium isotherms of these two gases on the 3D-printed monolith were measured at 303, 333, and 373 K by a gravimetric method. The adsorption capacities were compared to the ones of the original powder. The activated carbon materials showed a higher affinity to CH4. Furthermore, the adsorption equilibrium data of CO2 and Ar were also assessed. For all gases, the adsorption capacities decreased upon shaping. The monolith's CH4/N2 ideal selectivity was compared with its pristine powder (2.84 vs. 3.54). The CH4/N2 separation performance was also assessed through dynamic breakthrough tests. The experimental breakthrough curves were well predicted using a mathematical model.

Activated Carbon-Incorporated Tragacanth Gum Hydrogel Biocomposite: A Promising Adsorbent for Crystal Violet Dye Removal from Aqueous Solutions.

Biomaterials-based adsorbents have emerged as a sustainable and promising solution for water purification, owing to their eco-friendly nature and remarkable adsorption capacities. In this study, a biocomposite hydrogel was prepared by the incorporation of activated carbon derived from pomegranate peels (PPAC) in tragacanth gum (TG). The hydrogel biocomposite (PPAC/TG) showed a porous structure, a negative surface charge at a pH of more than 4.9, and good stability in aqueous media. The adsorption properties of the PPAC/TG hydrogel biocomposite were assessed for the removal of crystal violet dye (CV) from aqueous solutions using a batch adsorption. The equilibrium adsorption data followed the Sips isotherm model, as supported by the calculated R2 (>0.99), r-χ2 (<64), and standard error values (<16). According to the Sips model, the maximum values of the adsorption capacity of PPAC/TG were 455.61, 470.86, and 477.37 mg/g at temperatures of 25, 30, and 35 °C, respectively. The adsorption kinetic of CV onto the PPAC/TG hydrogel biocomposite was well described by the pseudo-second-order model with R2 values more than 0.999 and r-χ2 values less than 12. Thermodynamic studies confirmed that the CV dye adsorption was spontaneous and endothermic. Furthermore, the prepared hydrogel exhibited excellent reusability, retaining its adsorption capacity even after being used more than five times. Overall, this study concludes that the prepared PPAC/TG exhibited a significant adsorption capacity for cationic dyes, indicating its potential as an effective and eco-friendly adsorbent for water treatment.

High efficiency removal of Congo red from wastewater by metal organic framework material UiO-66

Abstract The Zr-based metal organic framework UiO-66 was synthesized using the solvothermal method. The adsorption properties of UiO-66 for organic dye Congo red (CR) were studied. The results showed the excellent adsorption performance of UiO-66 toward CR. The adsorption equilibrium data were consistent with the Langmuir adsorption isotherm model. The adsorption kinetics, thermodynamics, and mechanism of CR on UiO-66 were studied. The results of cyclic adsorption experiments showed that UiO-66 could be used repeatedly to adsorb CR.

Removal of Methylene Blue by adsorption onto natural and purified clays: Kinetic and thermodynamic study

The present work explores the optimization of experimental conditions for the adsorption of the organic cationic dye methylene blue (MB) by natural and purified clays. The adsorption capacities of samples were determinate to evaluate the efficiency of the purification process. At first, we performed mineralogical and textural analysis of the clay minerals, namely, smooth clay (SC), rigorous clay (RC) and bentonite clay (BC), using various techniques, particularly, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray fluorescence (XRF). The characterizations data showed that SC and RC are mainly composed of smectite associated with kaolinite, illite and chlorite. While BC is considered a mesoporous and swelling clay with smectite as the major component. The cation exchange capacity (CEC) was determinate as a 6.30 meq/100 g, 10.69 meq/100 g and 32.64 meq/100 g for SC, RC and RC natural samples respectively. It was noticed that the CEC as well as the specific surface area increase once the impurities associated with the clay are removed. A preliminary study was carried out to elucidate the influence of different parameters; such as contact time, exchangeable cation, solute concentration, temperature and pH on MB adsorption in aqueous solution by clays. The adsorption equilibrium data were analyzed by the linear and nonlinear forms of the Langmuir and Freundlich isotherm models. The Langmuir isotherm fitted well with the experimental data, and the pseudo-second-order kinetic model represented appropriately the adsorption kinetics of MB dye. Moreover, purified clays showed improved adsorption capacity for MB compared to pristine ones: 147.64; 257.69 and 1383 mg/g versus 128.75; 193.4 and 681.85 mg/g for SC, RC and BC respectively. This is attributed to a suitable specific surface, ion exchange capacity and electrostatic interactions as result of a more adequate texture and composition of our treated clays. The thermodynamic studies reveled negative Gibbs free energy change (ΔG) values (from -6.293 to -18.608 KJ.mol−1), positive enthalpy change (ΔH) values, exceeding 40 kJ/mol and positive entropy change (ΔS) values confirming the spontaneous, endothermic and chemisorption nature of the MB adsorption process. The results show that the tested purified clays are efficient in MB removal and can be used as an alternative to the commercial adsorbents, which are often relatively expensive.

Efficient fluoride removal from aqueous solution by sorption using natural adsorbent - Eugenia Jambolana: Equilibrium isotherm analysis and influence of anions

Commercial industries which employ metallurgical extraction, cement manufacturing and fuel cells expulse heavy volumes of fluoride-containing wastewater into the natural environment posing grave threats to public health. In the current study, a locally available plant known as Jamun (Eugenia Jambolana), was used as an adsorbent for fluoride removal from aqueous solutions. Physico-chemical experiments were conducted to reveal the size and surface distribution of natural fluoride adsorption on the adsorbent surface using SEM, XRD, and FT- IR. Effects of different parameters such as solution pH, adsorbent dosage (m), co-ions contact time (t), fluoride concentration, and flow rates were investigated. Additionally, the adsorption efficiency of competing ions like Cl-, NO3-, SO42-, PO43-, Ca2+, and Mg2+ and their physiological effects were studied under different solution concentrations ranging from 20 – 200 mg / L at pH 6.90±0.10 for 1 hour. Results showed that the adsorption equilibrium and kinetic data were matched with the isotherm Langmuir model (R2 = 0.98) and Freundlich model (R2 = 0.97). Also, we could conclude that the adsorption process of fluoride using the natural adsorbent resu bivalve shells was an endothermic reaction and resulted in a spontaneous adsorption process. Adsorption kinetic models revealed a swift adsorption rate with minimum and maximum fluoride concentrations as 100 mg / L and 500 mg / L with contact time (t) = 60 minutes at adsorbent dosage (m) = 1 g / L.

Olive stone as an eco-friendly bio-adsorbent for elimination of methylene blue dye from industrial wastewater

Adsorbents synthesized by activation and nanoparticle surface modifications are expensive and might pose health and ecological risks. Therefore, the interest in raw waste biomass materials as adsorbents is growing. In batch studies, an inexpensive and effective adsorbent is developed from raw olive stone (OS) to remove methylene blue (MB) from an aqueous solution. The OS adsorbent is characterized using scanning electron microscopy (SEM), Fourier Transform Infra-Red (FTIR), and Brunauer–Emmett–Teller (BET) surface area. Four isotherms are used to fit equilibrium adsorption data, and four kinetic models are used to simulate kinetic adsorption behavior. The obtained BET surface area is 0.9 m2 g−1, and the SEM analysis reveals significant pores in the OS sample that might facilitate the uptake of heavy compounds. The Langmuir and Temkin isotherm models best represent the adsorbtion of MB on the OS, with a maximum monolayer adsorption capacity of 44.5 mg g−1. The best dye color removal efficiency by the OS is 93.65% from an aqueous solution of 20 ppm at the OS doses of 0.2 g for 90 min contact time. The OS adsorbent serves in five successive adsorption cycles after a simple filtration-washing-drying process, maintaining MB removal efficiency of 91, 85, 80, and 78% in cycles 2, 3, 4, and 5, respectively. The pseudo second-order model is the best model to represent the adsorption process dynamics. Indeed, the pseudo second-order and the Elovich models are the most appropriate kinetic models, according to the correlation coefficient (R2) values (1.0 and 0.935, respectively) derived from the four kinetic models. The parameters of the surface adsorption are also predicted based on the mass transfer models of intra-particle diffusion and Bangham and Burt. According to the thermodynamic analysis, dye adsorption by the OS is endothermic and spontaneous. As a result, the OS material offers an efficient adsorbent for MB removal from wastewater that is less expensive, more ecologically friendly, and economically viable.