Adsorption Isotherm Models Research Articles

Fabrication of Fe3O4@Polypyrrole@Sulfamic Acid Composite for Efficient Adsorption of Four Cationic Dyes in Aqueous Solution

ABSTRACTWith the continuous development of industry, the issue of industrial wastewater emissions is increasing. Adsorption, as an effective means possessing the features of no pollution, high efficiency, and easy operation, has become one of the effective methods to treat industrial wastewater. Fe3O4@polypyrrole@sulfamic acid (Fe3O4@PPy@SA) composite is successfully prepare by hydrothermal method, in situ polymerization, and modification. Its adsorption behaviors of the composite on MG, MB, CV, and RhB are investigated by UV–Vis, and the impacts of temperature, dye concentration, and the contact time between the composite and the dyes on the adsorption efficiency are researched. The adsorption kinetics and adsorption isotherms exhibit that the adsorption of these four dyes is more in accordance with pseudo‐second‐order kinetic model and Langmuir adsorption isotherm model, the diffusion behaviors are affected through the combined effect of intraparticle diffusion and Boyd membrane diffusion, and the thermodynamic studies display that all these adsorption behaviors are spontaneous heat absorption behaviors. The prepared Fe3O4@PPy@SA is an efficient adsorbent in the field of applications.

In Situ Synthesis of Zr-Doped Mesoporous Silica Based on Zr-Containing Silica Residue and Its High Adsorption Efficiency for Methylene Blue

Zr-containing silica residue (ZSR) is an industrial by-product of ZrOCl2 production obtained through an alkali fusion process using zircon sand. In this study, low-cost and efficient Zr-doped mesoporous silica adsorption materials (Zr-MCM-41 and Zr-SBA-15) were prepared in one step via the hydrothermal synthesis method using ZSR as the silicon source for the removal of methylene blue (MB) from dye-contaminated wastewater. The samples were characterized using X-ray fluorescence (XRF) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetry (TG), and N2 adsorption–desorption measurements. The findings indicate that the synthesized Zr-MCM-41 and Zr-SBA-15 possess highly ordered mesoscopic structures with high specific surface areas of 910 and 846 m2/g, large pore volumes of 1.098 and 1.154 cm3/g, and average pore diameters of 4.18 and 5.35 nm, respectively. The results of the adsorption experiments show that the adsorbent has better adsorption properties under alkaline conditions. The adsorption process obeys the pseudo-quadratic kinetic model and the Freundlich adsorption isotherm model, indicating the coexistence of physical and chemisorption processes. The maximum adsorption capacities of Zr-MCM-41 and Zr-SBA-15 are 618.43 and 516.58 mg/g, respectively, as calculated by the Langmuir model (pH = 9, temperature of 25 °C). Compared with mesoporous silica prepared with sodium silicate as the silicon source, Zr-MCM-41 and Zr-SBA-15 have different structural properties and better adsorption properties due to Zr doping. These findings indicate that ZSR is the preferred silicon source for preparing mesoporous silica, and the mesoporous silica prepared using Zr silicon slag is a promising adsorbent and has great application potential in wastewater treatment.

Carboxymethyl cellulose sodium/bentonite composite adsorbent for Cd(II) adsorption from wastewater

Severely polluting wastewater containing heavy metal ions has become a pressing issue. To address the current shortcomings of natural bentonite (Bent) and carboxymethyl cellulose sodium (CMC) for Cd(II) adsorption, this study developed a cellulose/bentonite composite adsorbent (CMCMW-Bent) via microwave-assisted synthesis using acrylic acid (AA)-modified CMC and pretreated bentonite (Bent), and the adsorbent was used to remove Cd(II) from wastewater. The results show that the strong interaction between AA and CMC, which successfully entered the bentonite layer, and the bentonite provided excellent structural stability and abundant adsorption sites for the adsorption process. Meanwhile, microwave-assisted heating enhanced this unique structure compared to traditional heating with the aqueous solution. The best adsorption effect occurred at pH = 6–7, with a maximum adsorption capacity of 44.76 mg/g for Cd(II). The isothermal adsorption and kinetic models demonstrate that the adsorption process followed the Langmuir adsorption fitting and pseudo-second-order kinetic equations. The thermodynamic study confirms that the adsorption process was a spontaneous endothermic process and a chemical adsorption process. This study provides a new approach for obtaining efficient adsorbents.

Effective removal of heavy metal ions (Pb, Cu, and Cd) from contaminated water by limestone mine wastes

Limestone mining waste and its derived CaO were checked as an adsorbents of pb2+, Cu2+, and Cd2+ ions from water solution. The characterization of Limestone and calcined limestone was studied by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Scanning Electron Microscope (SEM), and Surface area measurements (BET). The optimum conditions of sorbent dosage, pH, initial concentration, and contact time factors were investigated for pristine limestone and calcined limestone absorbents. The results indicate that the optimum initial concentrations of (Ci) were 1200, 500, and 300 ppm for Pb, Cu, and Cd, respectively, using calcined limestone adsorbent, while using the pristine limestone adsorbent, the corresponding optimum initial concentrations were 700, 110, and 50 ppm. In the ternary system sorption, the results indicated that the selectivity sequence of the studied metals by limestone can be expressed as Pb2+ > Cd2+ > Cu2+, while calcined limestone exhibits a higher selectivity for Pb2+ compared to Cu2+ and Cd2+. Hence, various adsorption isotherm and kinetic models were examined to explore different patterns and behaviors of adsorption. So, the results indicate that calcined limestone has great potential for eliminating cationic heavy metal species from industrial water solutions.

Experimental investigation of pyridine removal using vulcanized oil shale

The study systematically conducted orthogonal and univariate experiments to determine the optimal parameters for pyridine removal using vulcanized oil shale. The findings revealed that the key determinants of pyridine adsorption onto vulcanized oil shale included the pH level of the pyridine solution, contact time, initial pyridine concentration, and the quantity of vulcanized oil shale introduced into the system. Under optimal adsorption conditions, the vulcanized oil shale achieved a 48.00% adsorption efficiency and an equilibrium adsorption capacity of 4.83 mg·g−1. In contrast, the untreated oil shale exhibited a comparatively reduced adsorption efficiency of 22.88% under its respective optimal conditions. The research further examined the adsorption kinetics and isothermal adsorption models for both types of oil shale. The kinetic data indicated that pyridine adsorption followed a pseudo-second-order model. The pyridine adsorption isotherms for both oil shale and vulcanized oil shale were best described by the Freundlich model, compared to the Langmuir model. These findings provide significant insights into the utilization of vulcanized oil shale for the efficient treatment of low-concentration pyridine wastewater, potentially contributing to environmental remediation and pollution control strategies.

Loading of anionic surfactant on eco-friendly biochar and its applications in Cr(VI) removal: adsorption, kinetics, and reusability studies

Surfactant-modified biochar is a viable adsorbent for eliminating Cr(VI) from synthetic wastewater. The biochar obtained from the zea mays plant (BC) was tailored with sodium dodecyl sulfate (SDS) as an anionic surfactant forming SDS-BC adsorbent. Different controlling conditions have been evaluated including pH of the solution, biomass concentration, primary Cr(VI) concentration, time of adsorption, and temperature. Under the best controlling circumstances, the percentage of removal has attained 99%. The pseudo-second-order kinetic model best described the removal process, according to the kinetic data, while the Temkin model, one of the applicable adsorption isotherm models, well expressed the adsorption process. The thermodynamic parameters were computed, which disclosed the spontaneity and exothermic character of the Cr(VI) elimination. According to the regeneration cycles, SDS-BC was cost-effective and had a good removal capability.Graphical

Study on stabilization of mercury in wastewater and soil by modified coal-based humic acid residue.

Coal-based humic acid residue (HAS), as a waste generated during humic acid production, has been gaining attention in recent years due to its adsorption capacity and containing nutrients. In this study, to improve the adsorption capacity of HAS for and Hg, phosphate-modified materials (N-HAS) were prepared by a hydrothermal method and HAS and N-HAS were characterized by scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), X-ray fluorescence (XRF); batch adsorption experiments investigated the adsorption capacity of N-HAS on Hg2+ under different pH, and isothermal adsorption model and kinetic model fitted the adsorption process to explore the adsorption mechanism; the effects of various amounts of N-HAS on the Hg content in maize and the effective Hg in the soil under Hg-contaminated soil were investigated by field trial. The results showed that the pseudo-second-order kinetic model (R2=0.9641) and Langmuir isothermal (R2=0.95) adsorption model could better describe the adsorption behavior of N-HAR on Hg2+, the maximum adsorption amount was 124.20 mg/g, and the time to reach adsorption equilibrium was shorter for N-HAS compared to HAS; after 5 times of adsorption-desorption, the removal rate of Hg2+ by N-HAS was still higher than 80%, with stable cyclic adsorption performance; the adsorption mechanism of Hg2+ by N-HAS included physical adsorption, precipitation, and surface complexation, and compared with HAS, the percentage of complexation for Hg2+ adsorption by N-HAS increased by 77.81%, and the percentage of precipitation increased by 7.68%; compared to the control group, it was shown that the addition of N-HAS significantly decreased (p < 0.05) the Hg content of maize kernels by 27.44% ∼ 72.09%, increased biomass by 4.34% ∼ 11.26%, and decreased the available Hg content in soil by 50.00% ∼ 82.80%. In addition, the addition of N-HAS at 0.4 kg/m2 was optimal for the field trial. The study showed that N-HAS not only achieved resource utilization but also demonstrated great potential for treating Hg2+ in water and soil.

A novel adsorbent based on duck feather for nitrate removal

In this study, the surface of duck feather was modified with (3-chloropropyl) trimethoxysilane and (1,4-diazabicyclo[2.2.2]octane), and it was used as a natural polymeric adsorbent to remove nitrate ion from a solution. The prepared modified duck feather was characterized using TGA, FT-IR, and FE-SEM analyses. The study examined the effect of various parameters such as pH, contact time, adsorbent dosage, and initial concentration of nitrate on adsorption efficiency. pH = 7, 40 min contact time, 30 mg of adsorbent, and 40 mg/L initial concentration of nitrate were found as the optimum conditions offering the maximum efficiency of 91.85% and maximum adsorption capacity of 30.62 mg/g. Also considered were various competing anions together with nitrate ions in the solution. The results revealed that maximum nitrate adsorption could be obtained in the presence of phosphate anion via ion exchange mechanism. It could also offer the best fit for the adsorption isotherm and kinetic model for Langmuir and pseudo-second-order models. The investigation of thermodynamic parameters at 25 °C revealed that the ΔG°, ΔH°, and ΔS° were obtained −5.44, −46.56, and −0.14 kJ mol−1 K−1, respectively.

Evaluation of the efficiency of shell powder as a natural adsorbent for the adsorption of chromium in aqueous solutions: kinetic and thermodynamic approach and modeling of adsorption isotherms

Water pollution by heavy metals such as chromium is a major environmental issue requiring effective remediation solutions. In this study, shellfish powder was used as a natural material to adsorb chromium (III) from aqueous solutions. The results show that shellfish have a significant adsorption capacity, indicating their effectiveness under a variety of conditions. Adsorption kinetics tests showed that the adsorption mechanism followed a pseudo-second-order kinetic model. In addition, thermodynamic parameters show that the adsorption process is a beneficial, spontaneous and endothermic phenomenon. Isotherm models such as Langmuir, Freundlich and Temkin were applied to analyze adsorption behavior. This research could contribute to the development of more sustainable wastewater treatment methods, incorporating natural materials into remediation strategies.

Preparation of Porous Novel QuEChERS Adsorbent ZIF‐67/PAA/PES Composite Microspheres and Their Application for Rapid Adsorption of Triphenylmethane Dyes in Wastewater and Fish

ABSTRACTTriphenylmethane dyes have a wide range of applications in textiles, pharmaceuticals, food, and other fields. Malachite green (MG), fuchsin acid (FA), and crystalline violet (CV) were typical representatives of triphenylmethane dyes, and they are carcinogenic and mutagenic to aquatic organisms and environment. However, they need to be separated and enriched for their accurate quantification due to their low content. Therefore, it is important to develop a rapid and accurate enrichment method to monitor these dyes in aquatic systems for human health. In this paper, a novel QuEChERS adsorbent porous ZIF67/PAA/PES composite microspheres were prepared and applied for the rapid adsorption of triphenylmethane dyes in wastewater and fish samples, which improved the adsorption capacity and the analytical sensitivity of the targets. The experimental results demonstrated that the porous ZIF‐67/PAA/PES composite microspheres exhibited excellent selective adsorption capacity of MG, FA, and CV, and after six adsorption–desorption cycles, the material adsorption amount can reach more than 90% of its original adsorption amount in wastewater. In addition, the porous ZIF67/PAA/PES composite microspheres were applied as QuEChERS adsorbents for the enrichment of MG and CV dyes in fish, and the adsorption rates of the dyes were 99.11% and 99.03%, with the RSDs of 1.58% and 1.27%, respectively. The limits of detection were 0.0093 and 0.0127 mg/L for MG and CV. Through the Langmuir adsorption isotherm models to predict the MG, FA, and CV of the maximum adsorption capacity were 5417.3622, 2119.9011, and 1654.1026 mg/g, respectively. Thus, the novel porous ZIF67/PAA/PES composite microspheres are more advantageous as QuEChERS adsorbents for sample pre‐treatment and have very important research significance.

Construction of carbon dot-embedded fluorescent hydrogels based on oxidized gum arabic-gelatin Schiff base for Cr(VI) detection applications.

In this study, a novel nitrogen-doped carbon quantum dot/oxidized gum arabic-gelatin-based fluorescent probe (NAH) was prepared using gelatin (GL) and gum arabic (AG) biomolecules. The primary network structure of this hydrogel consisted of polyacrylamide (PAM), while a secondary network structure was constructed between oxidized gum arabic and gelatin through the reaction of the Schiff base, which significantly enhanced the mechanical properties, the stress and strain of NAH reached 266.47KPa and 2175.75%. Nitrogen-doped carbon dots (NCDs) with yellow fluorescence emission properties were synthesized by hydrothermal method using salicylic acid as the carbon source and o-phenylenediamine as the nitrogen source. The fluorescent sensor obtained by compounding NCDs with hydrogel was able to selectively detect Cr(VI). The linear range of its detection was 0-90μM, and the detection limit was 0.19μM. The maximum theoretical adsorption capacity of the NAH hydrogel was 169.4mg/g, and its adsorption isotherm conformed to the Langmuir adsorption isotherm model, and the adsorption kinetics conformed to the quasi-secondary kinetic model. Compared with the NCDs solution, the NAH hydrogel showed superior comprehensive performance, especially in solving the problem of recovery of NCDs. Meanwhile, this hydrogel provides an effective insight into the efficient detection and adsorption of environmental pollutants.

Evaluation of carbon nanotubes/modified empty fruit bunch for adsorptive removal of methylene blue

Dyes pose a significant risk to water pollution due to their toxic components which endangers both the environment and human health. The present research is to investigate the effectiveness of carbon nanotubes (CNTs) that were mixed with modified empty fruit bunch (MEFB) for the elimination of Methylene Blue (MB) dye. The CNTs/MEFB was prepared using a simple reflux method. The findings indicated that 0.25g of adsorbent dosage has the high removal rate and 30 mg/l is the ideal initial concentration. The pH of 8 shows the excellent methylene uptake along with ideal temperature of 40°C. The Langmuir and Freundlich adsorption isotherm model were studied, and the equilibrium data was best discussed by the Langmuir isotherm model. Through the results obtained, CNTs/MEFB adsorbent shows an excellent result in Methylene Blue uptake.

Metal-organic framework functionalized magnetic Nb2CTX for high enrichment of polychlorinated biphenyls in water prior to gas chromatography tandem mass spectrometry

As a typical kind of persistent organic pollutants, polychlorinated biphenyls (PCBs) may cause great harm to human health. Recently, MXene has gained considerable attention due to its specific properties for the removal of pollutants by various principles. Present work reported a new functionalized MXene material, NH2-MIL-88 modified magnetic Nb2CTX, for developing a facile and efficient magnetic solid phase extraction method for enrichment and sensitive detection of PCBs in environmental water samples. The adsorption mechanism and parameters that may impact the extraction efficiencies of PCBs were explored. Gas chromatography-tandem mass spectrometry was utilized to detect the enriched PCBs. The results demonstrated that nine PCBs possessed good linearities in the range of 0.005 ∼ 50 μg L-1 and 0.005∼ 40 μg L-1, respectively. The detection limits of PCBs were over range of 0.06 - 0.28 ng L-1. The adsorption of PCBs on NH2-MIL-88 modified magnetic Nb2CTX followed quasi-second-order kinetic and Langmuir adsorption isotherm models. The fortified recoveries in real water samples ranged from 87.6% to103.4% (n = 3), which confirmed that the established method owned merits such as simplicity, rapidness, robustness, and high extraction efficiencies, and might be utilized for the detection of trace PCBs in environmental water samples.

Optimization of Nanobentonite-CuO Adsorption for Reducing 3-MCPDE, Free Fatty Acids, and Peroxide Values in Bulk Cooking Oil: A Study of Adsorption Efficacy and Isotherm Modeling

Indonesia is the largest palm oil producing country in the world. A factor that affects the quality of cooking oil is the presence of diglycerides and free fatty acids. Diglycerides in palm oil serve as precursors for the carcinogenic chemical 3-Monochloropropane-1,2-diol ester (3-MCPDE), whilst elevated concentrations of free fatty acids (ALB) might compromise oil stability. Numerous investigations indicate that the cooking oil present in the population includes the 3-MCPDE molecule at levels ranging from 8,150 to 58,140 ug/kg. The maximum permissible amount is 2 ug of 3-MCPDE per kilogram of body weight per day. The pillarization process involves the amalgamation of Cu(NO3)2 and NaOH inside an activated bentonite solution. The adsorption analysis of 3-MCPDE employing nanobentonite-CuO was performed using Gas Chromatography Mass Spectrometry (GC-MS) in accordance with the AOCE Cd 29a-2013 method, while free fatty acid and peroxide values were evaluated by a titration method that accounted for temporal variations. The peak efficacy of Nanobentonite-CuO in adsorbing the 3-MCPDE molecule was seen at 15 minutes, with an adsorption efficiency of 52.4%. Peroxide numbers achieved ideal performance at 45, 60, and 75 minutes, with an adsorption efficiency of 80%, whilst free fatty acids reached top performance at 75 minutes with an adsorption efficiency of 76.69%. The adsorption of 3-MCPDE compounds, free fatty acids, and peroxide content by Nanobentonite-CuO, as indicated by Adsorption Isotherm modeling, conforms to the Freundlich Isotherm, implying a physical adsorption mechanism.

One‐Pot Synthesis of Magnetically Recyclable Fe3o4@Uio‐66 Composite with Enhanced Oxytetracycline Adsorption Capacity

AbstractAs one of the most stable metal‐organic frame materials (MOFs), UiO‐66 has attracted extensive attention in the adsorption field. However, the application of UiO‐66 is still constrained by the weak electron‐hole charge separation capability and the low accessibility of micropores. In this study, the mesoporous defects of UiO‐66 were constructed with acetic acid and doped with Fe3O4 to prepare magnetically recyclable Fe3O4@UiO‐66. The doping of Fe3O4 resulted in the formation of denatured mesoporous defects in UiO‐66, which was conducive to adsorption oxytetracycline (OTC) in water. The crystal structure and physicochemical characteristics of Fe3O4@UiO‐66 were examined. By using the static adsorption technique, the adsorption characteristics and mechanism of OTC on Fe3O4@UiO‐66 were investigated. The results reveal that Fe3O4@UiO‐66 has an adsorption capacity of 210 mg g−1 and an OTC removal ratio of 84.0%. The pseudo‐second‐order kinetics, Elovich, and Langmuir isothermal adsorption models were all applicable to the adsorption process. The adsorption process increased entropy and was an endothermic reaction. Solution pH has a little effect on the adsorption performance. This study provides the possibility of one‐step synthesis of MOFs that can efficiently adsorb tetracycline antibiotics in water with low cost and excellent recyclability and reusablity.

New Insights on Iron-Trimesate MOFs for Inorganic As(III) and As(V) Adsorption from Aqueous Media.

Arsenic contamination of water endangers the health of millions of people worldwide, affecting certain countries and regions with especial severity. Interest in the use of Fe-based metal organic frameworks (MOFs) to remove inorganic arsenic species has increased due to their stability and adsorptive properties. In this study, the performance of a synthesized Nano-{Fe-BTC} MOF, containing iron oxide octahedral chains connected by trimesic acid linkers, in adsorbing As(III) and As(V) species was investigated and compared with commercial Basolite®F300 MOF. Despite their similarities in composition, they exhibit distinct structural characteristics in their porosity, pore size, and surface areas, which affected the adsorption processes. The kinetic data of the adsorption of As(III) and As(V) by both Fe-MOFs fitted the pseudo second-order model well, with the kinetic constant being higher for Basolite®F300 given its higher porosity. Intraparticle diffusion was, in both cases, the rate controlling step with the contribution of film diffusion in the adsorption processes, which achieved equilibrium after 1 h. The maximum adsorption capacity for As(V), 41.66 mg g-1, was obtained with Basolite®F300 at the 6.5-10 pH range, whereas Nano-{Fe-BTC} showed a different behaviour as maximum adsorption (14.99 mg g-1) was obtained at pH 2. However, both adsorbents exhibited the same performance for As(III) adsorption, which is not adsorbed at pH < 9. The Langmuir adsorption isotherm model fitted well for As(III) and As(V) adsorption by Nano-{Fe-BTC} and As(III) by Basolite®F300, whereas the Freundlich model fitted best for As(V) given its superior structural properties.

Nickel removal from synthetic wastewater by novel zeolite-doped magnesium- iron- and zinc-oxide nanocomposites by hydrothermal-calcination technique

This study aims to modify raw zeolite with metal oxide nanocomposites to remove nickel (Ni) ions from synthetic wastewater. Novel zeolite-doped magnesium oxide (MgO), iron oxide (Fe3O4), and zinc oxide (ZnO) nanocomposites were synthesized by hydrothermal-calcination methods. The novel zeolite-doped metal oxide nanocomposites were used as adsorbents to remove Ni (II) ions from synthetic wastewater. Several advanced techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometer (VSM) were applied to study the structural, morphological, chemical, and magnetic properties of the prepared materials. Doped zeolite with ZnO, MgO, and Fe3O4 significantly enhances the removal of Ni (II) ions from synthetic wastewater. The zeolite-doped MgO + Fe3O4 + ZnO sample achieved a Ni (II) ions removal efficiency of 99.6%, compared to 58.9% for raw zeolites. The removal efficiencies of Ni (II) ions (Ci = 30 mg/L) from highest to lowest were 99.56%, 99.53%, 91.4%, 67.8%, and 58.93% by zeolite-doped MgO + Fe3O4 + ZnO, zeolite-doped MgO, zeolite-doped ZnO, zeolite-doped Fe3O4, and raw zeolite sample, respectively. The highest adsorption capacity was 17.13 mg/g of zeolite-doped MgO + Fe3O4 + ZnO samples. The experimental adsorption data collected were fitted using five isotherm models, and four kinetic models. The Langmuir adsorption isotherm model and the pseudo-second-order kinetic model provided the best fit for the experimental adsorption data. This suggests that the adsorption process is complex, possibly involving electron interactions between the active sites of doped zeolite and Ni (II) species. The obtained data indicates that zeolite-doped with MgO, Fe3O4, and ZnO notably enhances the adsorptive properties of Ni (II) from synthetic wastewater. The obtained thermodynamic values confirmed that the adsorption process is spontaneous and endothermic, with increased randomness at the solid-solution interface during the adsorption process.

Cadmium adsorption onto aluminum hydroxide-modified attapulgite prepared with basic aluminum acetate

Cadmium pollution in water is becoming increasingly serious. Thus, the effective removal of Cd(II) from water has garnered attention. Aluminum hydroxide-modified attapulgite (ATP-AC) was prepared from basic aluminum acetate through a coprecipitation method that could efficiently adsorb Cd(II) in aqueous solution. Seven characterization methods were utilized to investigate the properties of ATP-AC. Batch experiments were carried out to research the effects of pH, adsorption time, Cd(II) concentration and dosage on the Cd(II) adsorption ability of ATP-AC. The results revealed that the optimal conditions for the adsorption of Cd(II) by ATP-AC were pH = 7, a dosage of 0.4 g L−1, and and equilibrium time of 6 h. The Freundlich adsorption isotherm model better described Cd(II) adsorption by ATP-AC than did the Langmuir model. The maximum adsorption capacities at temperatures of 293, 303 and 313 K were 5.55, 10.35 and 12.95 mg g−1, respectively. The pseudo-second-order kinetic equation was more appropriate for describing the adsorption of Cd(II) by ATP-AC than the pseudo-first-order kinetic equation was. The thermodynamic parameters indicated that Cd(II) adsorption by ATP-AC is endothermic and spontaneous and proceeds in the direction of disorder. The increased specific surface area and increased number of hydroxyl group active sites are the main reasons for the improved Cd(II) adsorption capacity of ATP-AC.

Development of Mn3(PO4)2 nanoplates assisted treatment strategy for the removal of cadmium from synthetic domestic wastewater

This study reports an adsorption treatment strategy for the removal of cadmium ions from wastewater using manganese (II) phosphate nanoplates (Mn3(PO4)2 NP) as adsorbent. The proposed method was combined with flame atomic absorption spectrometry to aid in quantification. Different concentrations of cadmium were spiked to synthetic domestic wastewater and applying the optimized treatment conditions yielded removal efficiency values in the range of 82–99%. An adsorption capacity (q e) of 16.4 mg/g was calculated for 25 mg/L Cd2+ under the optimum conditions of pH 9.0, 50 mg Mn3(PO4)2 NP and 60 s mixing by ultrasonication. Equilibrium values obtained using four types of Langmuir adsorption isotherm models were modeled mathematically, and the results showed that the Type 1 isotherm model fitted well with the experimental data. According to these results, the maximum adsorption capacity (q m) was calculated as 20.01 mg/g at optimum conditions. Removal efficiency and the established equilibrium between the adsorbent and the adsorbate validated Mn3(PO4)2 NPs as an effective adsorbent for the removal of Cd2+ from wastewater.

Hydrothermal сarbonization of Spirogyra sp. algae for adsorption and regeneration of malachite green dye

In this study, we prepared hydrochar (HCSP) from Spirogyra sp. algae (SP) as adsorbent to eliminate malachite green (MG) dye and conducted the adsorbent regeneration study. SP and HCSP were characterized using FTIR, XRD, SEM, and BET. The adsorption performance was evaluated under various conditions of pH, contact time, concentration, and temperature. SP and HCSP were optimum at pH 8 for MG adsorption. The suitable adsorption kinetics model was PSO, and the adsorption isotherm model tended to be the Freundlich model. The maximum adsorption capacity (Qmax) obtained from Langmuir calculation at 30 °C, SP and HCSP were 34.96 mg/g and 99.01 mg/g, respectively. The thermodynamic parameters indicated endothermic and spontaneous processes, with HCSP exhibiting greater adsorption capacity and spontaneity than SP. Regeneration studies demonstrated that HCSP and SP materials could be reused up to the 4th cycle with the remaining efficiency of 69.37% and 49.30%, respectively. Compared to SP, HCSP has better adsorption capacity.