Adsorption Kinetic Data Research Articles

Kinetic and equilibrium study of graphene and copper oxides modified nanocomposites for metal ions adsorption from binary metal aqueous solution.

Presently, the main cause of pollution of natural water resources is heavy metal ions. The removal of metal ions such as nickel (Ni2+) and cadmium (Cd2+) has been given considerable attention due to their health and environmental risks. In this regard, for wastewater treatment containing heavy metal ions, graphene oxide (GO) nanocomposites with metal oxide nanoparticles (NPs) attained significant importance. In this study, graphene oxide stacked with copper oxide nanocomposites (GO/CuO-NCs) were synthesized and characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and atomic force microscopy (AFM) analytical procedures. The prepared GO/CuO-NCs were applied for the removal of Ni2+ and Cd2+ ions from a binary metal ion system in batch and continuous experiments. The obtained results revealed that GO/CuO-NCs exhibited the highest removal efficiencies of Ni2+ (89.60% ± 2.12%) and Cd2+ (97.10% ± 1.91%) at the optimum values of pH: 8, dose: 0.25g, contact time: 60min, and at 50ppm initial metal ion concentration in a batch study. However, 4mL/min flow rate, 50ppm initial concentration, and 2cm bed height were proved to be the suitable conditions for metal ion adsorption in the column study. The kinetic adsorption data exhibited the best fitting with the pseudo-second-order model. The adsorption isotherm provided the best-fitting data in the Langmuir isotherm model. This study suggested that the GO/CuO nanocomposites have proved to be efficient adsorbents for Ni2+ and Cd2+ ions from a binary metal system.

Inhibiting release of phenanthrene from rice-crab coculture sediments to overlying water with rice stalk biochar: Performance and mechanisms

Rice crab coculture is a new ecological agriculture model combining rice cultivation and crab farming. Current research related to rice crab coculture only focuses on production theory and technical system establishment, while ignoring the potential ecological risk of Polycyclic aromatic hydrocarbon(PAHs) in rice crab coculture sediment. In this study, rice straw was used to make rice straw biochar to explore the performance and mechanism of inhibiting release of phenanthrene(PHE) from rice-crab coculture sediments to overlying water with rice stalk biochar. The kinetic and isotherm adsorption data were best represented by the Langmuir model and pseudo-second-order model with a maximum adsorption capacity of 53.35 mg/g at 12 h contact time. The results showed that PHE was released from the rice-crab substrate to the overlying water in dissolved and particle forms as a result of bioturbation, and the PHE concentrations in dissolved and particle forms were 20.9 μg/L and 14.22 μg/L, respectively. This leads to secondary ecological risks in rice-crab co-culture systems. This is related to dissolved organic carbon(DOC) carrying the dissolved PHE and total suspended solids(TSS) carrying the particle PHE in the overlying water. Due to its large specific surface area, rice straw biochar is rich in functional groups, providing multiple hydrophobic adsorption sites. After adding rice straw biochar at 0.5 % w/w (dry weight) dose, the removal efficiency of dissolved and particulate PHE in the overlying water were 78.99 % and 42.11 %, respectively. Rice straw biochar is more competitively adsorbed PHE in the overlying water than TSS and DOC. The removal efficiency of PHE from the sediment was 52.75 %. This study confirmed that rice stalk biochar could effectively inhibit PHE migration and release in paddy sediment. It provides an environment- friendly in situ remediation method for the management of PAHs pollution from crab crops in rice fields.

High efficiency and mechanisms of Cd2+, Cu2+, Mn2+ removal from aqueous solution by modified tobermorite

In this work, nanoscale magnesium oxide and activated carbon were simultaneously loaded on tobermorite through a gelation-calcination method. The new composite (TOB@C@MgO) was used as an effective adsorbent to remove Cd2+, Cu2+, and Mn2+ from aqueous solution and actual wastewater. Its specific surface area was determined to be 146.90 m2/g, and its sedimentation property was found to be satisfactory. At an initial ion concentration of 500 mg/L, a solution pH of 5.2 ± 0.2, an adsorbent dosage of 1.5 g/L, and a temperature of 25 °C, the adsorption equilibrium for Cd2+, Cu2+, and Mn2+ was reached within 2 h, 4 h, and 6 h, with a removal efficiency of 100 %, 90 %, and 64 %, respectively. The pseudo-second-order model and Langmuir model fitted the kinetic and isothermal adsorption data well. The maximum adsorption capacity for Cd2+, Cu2+, and Mn2+ by TOB@C@MgO, as calculated from the Langmuir model, was 1000.00 mg/g, 526.32 mg/g, and 416.67 mg/g, respectively. The selective sequence of metal ions by TOB@C@MgO was in the order of Cd2+ > Cu2+ > Mn2+. Besides, TOB@C@MgO demonstrated effective treatment of actual wastewater, and exhibited reasonably good reusability and stability. Different characterizations revealed that Cd2+, Cu2+, and Mn2+ removal by TOB@C@MgO was primarily dominated by ion exchange. Surface precipitation/complexation, interaction with π electrons, and physical adsorption also contributed to the fixation of Cd2+, Cu2+, and Mn2+ onto the surface of TOB@C@MgO.

Characterization of Magnetic Biochar Modified Using the One-Step and Electrochemical Methods and Its Impact on Phosphate Adsorption.

The properties and phosphate adsorption capability of the one-step method and electrochemical method in modifying peanut shell biochar have been determined. The one-step method deposits MgO and Fe3O4 onto biochar through chemical impregnation and regularly affects the functional groups and magnetic separation of biochar, thereby enhancing its ability to adsorb phosphate. In contrast, the electrochemical method is not favorable for modifying functional groups of biochar but can promote phosphate adsorption because of the formation of MgFe2O4 and Fe3O4 using electrolysis. The adsorption isotherm and kinetics data suggest that adsorption is monolayer onto a homogeneous surface and phosphate adsorption could be controlled by chemical processes. Biochar with the addition of both Fe2+ and Mg2+ shows better phosphate adsorption capability than those with barely any Fe2+ additions. It was concluded that the one-step method is a better modification method than the electrochemical method for enhancing the phosphate adsorption capability of biochars.

A composite based on hydroxyapatite biocrystal and poly(aniline-o-phenylenediamine) copolymer for efficient removal of anionic dyes from wastewater

BackgroundAcid dyes in any water source strongly impact its color, blocking sunlight and harming aquatic life. Herein, the technical applicability of a novel composite based on hydroxyapatite and poly(aniline-o-phenylenediamine) for removing dyes from synthetic wastewater was investigated using a batch method. MethodsIn this work, camel bones were used as a source of hydroxyapatite. Camel bones were pretreated in an alkali environment before extracting hydroxyapatite biocrystal (HAP). Subsequently, the extracted HAP was mixed with the poly(aniline-o-phenylenediamine) (PANI@PoPD) co-polymer. Different formulation methods were designed to optimize the tested composite samples' shape, size, structure and composition. Then, the optimized composite was further used as an adsorbent to remove orange G (OG) and thymol blue (TB) dyes from synthetic wastewater. The effects of the composite's dose, pH, dyes’ initial concentration and temperature on the overall performance of the composite were assessed. Statistical tests were then used to test the best experimental conditions to remove target dyes from wastewater. Significant findingsBy keeping the dye concentration constant at 50 mg/L for both OG and TB in wastewater at 25 °C, pH = 2 and 800 rpm of agitation speed in a batch reactor, it was found that the synthesized composite efficiently removes 99% of each dye at optimum dose of 0.5 or 1 g/L with a reaction time close to 30 or to 80 min for OG or TB, respectively. The predictive capacity of two-parameter models, including the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models, and three-parameter models such as the Redlich-Peterson, Sips and Toth models, was assessed to estimate the collected adsorption data. It was found that the statistical analysis was slightly better when the Temkin model was applied. This indicates that this equation was better suited to represent the experimental data of the adsorption of the OG dye. In contrast, the Redlich-Peterson and Toth models were in better agreement with the experimental results of the TB dye adsorption. Furthermore, thermodynamic parameters associated with each dye adsorption demonstrated its feasibility, while the adsorption kinetic data were found to be better described with the pseudo-second-order kinetics. In addition, the regenerability performances of the tested composite were successfully assessed by reusing the spent composite five consecutive times.

Rhodamine B sequestration using acid-precipitated and microwave-treated softwood lignin: Comparative isotherm, kinetics and thermodynamic studies

Sustainable development goals have emphasized the need to focus on water treatment to mitigate the ever-rising demands for clean water. High costs and energy requirements have been the Achilles’ heel of most treatment technologies. Herein, we develop cheap lignin-derived sorbents prepared by microwave (MW) and acid precipitation (AP) treatments of raw lignin (RL) for Rhodamine-B (RhB) adsorption in aqueous solution. Our findings evidence micro- and mesoporous structures, with irregular grain size. X-ray diffraction revealed an amorphous material, while Fourier-transform infrared analysis points to the presence of carboxyl, hydroxyl and sulfite functional groups, which may facilitate the adsorption of the dye. Adsorption isotherm and kinetic data describe complex and pore-driven interactions, based on the Sips, D-R and intraparticle diffusion models, considering the sum of squared error values obtained from nonlinear regression analysis. Adsorption efficiency of ∼97% is obtainable at optimal conditions for treated lignin (3 g/L sorbent dose, 720 min contact time and under acidic pH conditions). Thermodynamic studies revealed that RL-RhB and MW-RhB are driven by physisorption considering ∆H° values, while stronger interactions occurred for AP-RhB, considering the high enthalpy (∼49 kJ/mol) and adsorption capacity (∼2766 mg/g). Van der Waals attraction, π-π stacking, and pore-filling mechanisms are among the several interactions that may occur between RhB and the sorbents. Our findings offer a way to valorize lignin as an alternative pathway to economically viable and sustainable water purification.

Preparation and characterization of a novel nanocomposite based on MnCr-layered double oxide and CoFe2O4 spinel ferrite for methyl orange adsorption

Herein, the adsorption of methyl orange (MO), a dangerous anionic dye, from an aqueous solution was investigated using a novel magnetic nanocomposite adsorbent. A nanocomposite entitled manganese chromium-layered double oxide/cobalt spinel ferrite, (MnCr)-LDO5wt.%/CoFe2O4, which links the interlayer structural characteristics of layered double oxides (LDOs) with the magnetic properties of spinel ferrites (SFs) was synthesized using the eco-friendly co-precipitation technique. Determination of structural parameters, crystallite size, and micro-strain was done using X-ray diffraction (XRD) analysis. Transmission electron microscopy (TEM) was used to determine grain shape and size. Surface analysis was performed using X-ray photoelectron spectroscopy (XPS) to identify elements and oxidation states present in the prepared nanocomposite. Vibrating sample magnetometer (VSM) was utilized to examine the magnetic characteristic. A comprehensive comparative study about the effectiveness and durability of CoFe2O4 and (MnCr)5wt.%/CoFe2O4 as nanoadsorbents for MO was conducted. Numerous variables, including contact time, MO concentration, adsorbent dosage, and pH were tested for their effects on the adsorption removal percentages. The findings showed that the maximum removal percentage was 86.1% for 25 ppm of MO was for 0.1 g/100 mL of (MnCr)-LDO5wt.%/CoFe2O4 at pH = 3. Investigations of isotherms and kinetics were conducted under batch conditions. The Langmuir isotherm matched the experimental data, for both nanoadsorbents, quite well due to the homogeneous distribution of active sites. Adsorption kinetics data were found to be compatible with intra-particle diffusion and pseudo-second order models for CoFe2O4 and (MnCr)5wt.%/CoFe2O4, respectively. A total of five adsorption–desorption cycles were performed to determine the prepared adsorbents’ recyclable nature.

Preparation and characterization of acid-leached diatomaceous earth for application in the treatment of oily wastewater

This study evaluated the potential application of acid-leached diatomaceous earth in oily wastewater treatment. Acid-leached diatomaceous earth was prepared by treating diatomaceous earth using 2.2 M HNO3 to remove impurities. The leached diatomaceous earth was characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and Brunauer Emmett Teller (BET) analytical techniques to determine the crystallinity, elemental content, morphology and surface area, respectively. Response surface methodology (RSM) was employed to establish the optimum conditions on the treatment of oily wastewater using acid-leached diatomaceous earth. Elemental composition of acid-leached DE showed an increase in silica content reaching 91.57% from 78.98% and a decrease on elements such as CaO, K2O, MgO, and Fe2O3 associated with impurities such as carbonates and clay minerals. BET analysis showed an increase in pore volume and surface area from 60.88 to 68.71 Å and 15.02–22.40 m2/g following the acid leaching. The oil removal experiments revealed a maximum adsorption capacity of 124.16 mg/g and oil removal efficiency of 78.55% at an initial oil concentration of 3229.69 using 0.05 g adsorbent dosage and 119.20 min contact time. The adsorption kinetics data fitted better to pseudo-second order model (R2 = 0.98) of reaction kinetics indicating that adsorption occurred through chemisorption. The adsorption isotherms were described better by the Freundlich isotherms model (R2 = 0.87) indicating that adsorption occurred in a heterogeneous and multilayer surface. This study concluded that acid-leached DE has the potential for use in treatment of oily wastewater. However, further studies are encouraged to evaluate the regeneration and re-usability of the material.

A promising palm leaves waste-derived biochar for efficient removal of tetracycline from wastewater

Tetracycline (TC) is among the most commonly used antibiotics on the market today. As a result, huge amounts of TC-contaminated water enter the aquatic environment. This drug is considered an emerging pollutant and can cause acute problems for flora and fauna. Therefore, an efficient adsorbent is needed to remove TC from water bodies. Plant-based biochar can be a promising way to remove TC from water. In this work, a biochar (PLB) is made from dead palm leaves (PL), as a novel, eco-friendly, and effective adsorbent. The surface morphology and structural properties of the prepared adsorbent were confirmed by different characterization techniques. The results confirmed that the PLB has a higher surface area and more mesoporous hierarchical structure compared to raw PL. TC Adsorption experiments were carried out under different environmental conditions including contact time, solution pH, initial concentration of TC, adsorbent dose, and temperature. The adsorption kinetics data corroborated a pseudo-second order (PSO) model while the monolayer uptake capacity was found to be 13.71 mg/g and 6.52 mg/g for PLB and PL, respectively. The adsorption process was spontaneous and endothermic. The adsorbent exhibited regeneration capabilities for at least three consecutive cycles. The H-bonding, π-π interaction, electrostatic interaction, and pore-filling played a dominant role in TC adsorption. According to the study's findings, inexpensive biochar adsorbent is effective at removing TC and may also be used to potentially remove other toxins from vast amounts of wastewater samples.

Mechanisms for thallium(I) adsorption by zinc sulfide minerals under aerobic and anaerobic conditions

The highly toxic heavy metal thallium is widely distributed in sulfide ores and released into the environment by sulfide mining. However, the interface between the sulfide minerals and Tl(I) is unclear. In this study, the capacity for adsorption of thallium(I) by a common sulfide mineral (zinc sulfide) was investigated in aerobic and anaerobic environments, which revealed three mechanisms for adsorption on the ZnS surface (surface complexation, electrostatic action and oxidation promotion). Batch experiments indicated that the Tl(I) adsorption capacity of ZnS in an aerobic environment was approximately 9.3% higher than that in an anaerobic environment and was positively correlated with the pH. The adsorption kinetic data showed good fits with the pseudosecond-order model and the Freundlich isotherm model. The Tl(I) adsorption mechanism varied in different oxidative and pH environments. XPS, FTIR, and EDS results implied that complexation with surface hydroxyl groups was involved in the adsorption process. pH experiments and zeta analyses suggested that electrostatic attraction was also involved. Surface complexation and electrostatic attraction were the dominant mechanisms at pH values above 6. Furthermore, oxidative dissolution of ZnS and hydrolysis of Zn2+ enhanced the complexation with hydroxyl groups on the mineral surface and facilitated Tl adsorption. In this study, this interface mechanism provided new insights into thallium migration in sulfurized mineral environments in aerobic and anaerobic transition regions.

Analytical study on lead elimination by anionic clays: Characterization, adsorption kinetics, isotherm, thermodynamic, mechanism and adsorption

The co-precipitation method synthesized the synthetic anionicMg–Al and Ni-Al clays with three molar ratios (Mg/Al, Ni/Al). The samples were characterized by powder XRD, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). No other crystalline phases were detected in the powder XRD patterns of the co-precipitated samples. The infrared spectra obtained all the functional groups that characterize these two types of anionic clays. SEM micrographs indicate the presence of particles and aggregates. The particles, or aggregates, are in the form of plates, supported by particles of acceptable sizes. The optimal pH for maximum lead adsorption is about 6.5 for both clays. The optimal adsorbent masses for the maximum percentages of lead removal are 0.2 g for Mg3AlCO3 and 0.25 g for Ni3AlCO3. The Mg3AlCO3 has a maximum adsorption capacity of lead, where qm=73.42 mg g-1. The adsorbed amount increases with increasing temperature for both types of clays studied. The equilibrium time of Pb2+ adsorption is reached after 5 min for both clays. The most appropriate models to describe the experimental data of adsorption kinetics and isotherms are pseudo-second-order and Langmuir. The detection limit (LOD) was 0.272 mg L-1. The linearity range was 1 to 5 mg L-1(R2 0.9997).

Novel application of (NH4)2Mo3S13 for vanadium adsorption: Experiments, characterization, kinetic and equilibrium modeling

The adsorption of vanadium on (NH4)2Mo3S13 was analyzed via experimental and theoretical approaches. Kinetic and equilibrium adsorption data were quantified at 293–323 K and pH 3.2. Vanadium kinetics followed a pseudo-first order equation with adsorption rate constants ranging from 0.006 to 0.032 min−1, while the maximum experimental vanadium adsorption capacities ranged from 9.9 to 362 mg/g under tested operating conditions. Equilibrium data were fitted by a monolayer model that considered that the vanadium ions were removed via two different active sites of (NH4)2Mo3S13 surface. These adsorption sites were related to the Mo moieties of this material. The calculated adsorption capacities of these active sites followed the next trend: Q1 (293 K) > Q2 (293 K), Q2 (303 K) > Q1 (303 K) and Q2 (313 K) > Q1 (313 K). In particular, the calculated saturation vanadium adsorption capacities were 124 – 376 mg/g. The impact of adsorption temperature on the calculated number of vanadium ions that were adsorbed by both active sites was also studied. It was concluded that the temperature facilitated the adsorption of vanadium ions via the first active site of (NH4)2Mo3S13 surface, while an opposite trend was identified regarding the second type of active site. The interaction energies involved in the adsorption of both active sites were also calculated. These results indicated that both sites contributed in different degree to reduce the vanadium concentrations in the aqueous solutions for depollution purposes. Overall, this study provides useful insights on the vanadium adsorption mechanism for an alternative and competitive adsorbent, which is promising to be implemented in large-scale water purification systems.

High biosorption of cationic dye onto a novel material based on paper mill sludge

The valorization of paper mill sludge (PMS) is the main goal of this study. The emissions of PMS continue to increase at global scale, especially from packaging paper and board sectors. The raw sludge was used to prepare an adsorbent to remove toxic pollutants from wastewater, the methylene blue (MB), an organic dye. Firstly, the physico-chemical characterization of PMS was done determining the crystalline phases of PMS fibers, the content of main elements, and the pH zero point charge, which was determined at around pH 7. The adsorption of MB on PMS powder was studied at 18 °C with an agitation of 200 rpm, being the best operating conditions 30 min of contact time, 250 mg L−1 of initial MB concentration and 0.05 g in 25 mL of adsorbent dose. Experimental data of MB adsorption was fitted to Langmuir and Freundlich isotherm equations. The Langmuir model was more accurate for the equilibrium data of MB adsorption at pH 5.1. The PFOM and PSOM were adjusted to experimental adsorption kinetics data, being PSOM, which describes better the MB adsorption by PMS powder. This was confirmed by calculating the maximum adsorption capacity with PSOM, which was 42.7 mg g−1, being nearly similar of the experimental value of 43.5 mg g−1. The analysis of adsorption thermodynamics showed that the MB was adsorbed exothermically with a ΔH0 = − 20.78 kJ mol−1, and spontaneously with ΔG0 from − 0.99 to − 6.38 kJ mol−1 in the range of temperature from 291 to 363 K, respectively. These results confirm that the sludge from paper industry can be used as biosorbent with remarkable adsorption capacity and low cost for the treatment of wastewater. PMS can be applied in the future for the depollution of the effluents from the textile industry, which are highly charged with dyes.

Green synthesis of ZnO nanoparticles for spent caustic recovery: Adsorbent characterization and process optimization using I-optimal method

Clean and potable water is a basic human need for survival on Earth. Among the available water sources, wastewater has become increasingly valuable. However, certain types of wastewaters, such as spent caustic, are considered highly polluted and pose significant environmental hazards, making their proper treatment imperative. To address this issue, the present study focuses on developing a cost-effective and environmentally friendly solution using a ZnO nanocomposite synthesized with Iranian green tea as an adsorbent for sulfide adsorption from spent caustic wastewater. The synthesized nanoparticles were characterized using various analytical tools, including XRD, FTIR, FE-SEM, PSA, and EDX. The experiments were designed using Design Expert software to examine the impact of initial concentration, nanoparticle loading, initial pH, and time, leading to the determination of the optimum conditions. The optimized parameters for spent caustic recovery with spherical ZnO nanoparticles, obtained through the I-optimal method, were a nanoparticle loading of 0.37 wt%, an initial concentration of 777.5 ppm, a reaction time of 14.33 min, and a pH of 9.85, resulting in a remarkable 97% sulfide elimination. The adsorption isotherm and kinetics data indicated that the pseudo-second-order kinetics and Langmuir isotherm models were well-suited for sulfide elimination. Additionally, the ZnO nanoparticles exhibited the advantage of recyclability, maintaining up to 65% of their adsorption efficiency over five cycles. Consequently, the implementation of ZnO nanoparticles emerges as a promising and effective strategy for removing sulfide from spent caustic wastewater.

Enhancing the efficiency of Ni(II), Cd(II), and Cu(II) adsorption from aqueous solution using schist/alginate composite: batch and continuous studies.

The main aim of this research is focused on the synthesis of schist/alginate composite (SC/AL) adsorbent and its utilization for the removal of Ni(II), Cu(II), and Cd(II) from waste streams using batch and column processes. The characterization of developed adsorbent was performed by X-ray fluorescence, X-ray diffraction, FTIR, and BET analyses. The most influential operating parameters (pH, contact time, temperature and initial adsorbate concentration) on the adsorption capacity of pollutants were examined to evaluate the performance of developed adsorbent. The kinetic and equilibrium adsorption results at pH 5.0 indicated that SC/AL composite had good adsorption capacity (qmax) for Ni(II), Cu(II), and Cd(II) estimated at 124.79 mg/g, 111.78 mg/g, and 119.78 mg/g, respectively. From the kinetic viewpoint, the good fit of pseudo-first-order kinetic model to the kinetic adsorption data indicated that dominant interaction of heavy metals with SC/AL composite was physisorption. The results of thermodynamic studies indicated that the adsorption of heavy metals onto SC/AL composite was endothermic and spontaneous in nature. The adsorption capacity of developed adsorbent could still reach relatively 85% of the original one after completing fifth cycle. Therefore, the reusability results of SC/AL composite were quite satisfied, making the developed adsorbent a commercially attractive and green method. Finally, in column studies, the effect of initial concentration of pollutants at pH 5.0 on the removal of heavy metal ions was investigated. The Thomas and Yoon-Nelson models provided a satisfactory explanation for the results of column data.

Synthesis, characterization, and CO2 adsorption properties of pure ETS-10

Synthesis of titanosilicate ETS-10 with high purity and crystallinity is a big challenge due to its limited crystallization region. ETS-10 was synthesized and characterized by SEM, EDX, BET, and TGA/DTA methods. The effect of synthesis parameters including pH of the gel, crystallization temperature and time, and the potassium source, were studied using the one-at-a-time (OFAT) approach. The results showed that the ETS-10 with the highest purity was achieved considering the gel pH of 11.3, and the crystallization time and temperature of 72 h and 230 °C. It was also revealed that there was considerable interaction between the potassium source with other synthesis parameters. Afterward, CO2 adsorption of the pure synthesized sample was obtained at 298 K using a volumetric setup. The Dual-site Langmuir, Toth, and UNILAN isotherms were applied to model the obtained equilibrium adsorption data. The CO2 adsorption capacity of the synthesized pure ETS-10 was obtained equal to 3.37 mmol/g. Finally, the adsorption kinetics data were modeled using the PNO model with n = 3.5. The results showed that about 90% of the equilibrium absorption was achieved in only 25 s, which indicates the remarkable capability of using pure ETS-10 for CO2 capture by the PSA method.

In-situ synthesis of efficient ZnCl2 doped pyrolyzed biochar for adsorptive remediation of organic dyes: Performance evaluation, mass transfer and mechanism

Effective management of harmful contaminants from waste effluent is crucial for a sustainable environment. Herein, the efficient adsorbent, sawdust-derived biochar doped with ZnCl2 (Z@SB) for removal of organic dyes, namely malachite green (MG) and methyl orange (MO), was explored via batch adsorption study. A detailed characterization of the synthesized adsorbent was conducted to determine its physiochemical properties. The specific surface area of Z@SB from BET analysis improved 5.66 times after chemical modification. Moreover, the decolorization efficiency of the dyes onto Z@SB was investigated through analyzing the impact of initial pH, adsorbent dose, and contact time of the process. The Langmuir isotherm analysis revealed the maximum adsorption capacity (Qmax) of MG and MO dyes were 318.47 and 225.73 mg/g, respectively. The adsorption kinetics data of both dyes was well described by the pseudo-second-order model. Furthermore, Boyd's film diffusion model was employed to assess the diffusion mechanism and determine the rate-limiting step using the kinetic data obtained from batch adsorption experiment. Possible mechanisms for the removal of dyes onto Z@SB included hydrogen bonding, π-π bonding, and electrostatic interactions. The superior regeneration and reusability properties observed in Z@SB make it a highly promising adsorbent for effective utilization in real-field wastewater treatment applications.

Covalent assembly synthesis of covalent organic framework and MXene based composite for the adsorption of fluoroquinolones

Widespread use of fluoroquinolones (FQs) leads to its continuous excretion and release into the environment, resulting in the accumulation in water, animal-derived food etc., and posing a threat to environment and humans. Thus, the development of highly efficient FQs removal methods is of great significance. Herein, a composite (COF@MXene) was manufactured using a covalent assembly synthesis strategy by connecting covalent organic frameworks (COF) and NH2-MXene through a Schiff-base reaction. COF@MXene had the advantages of both COF and MXene, not only had good crystallinity, thermal stability and rich functional group properties, but also had high protein exclusion ability (Exclusion efficiency>97%) and good adsorption capacities for FQs including ciprofloxacin (CIP), lomefloxacin (LOM), moxifloxacin (MOX), gatifloxacin (GAT) and levofloxacin (LEV). The maximal adsorption capacities for them ranged from 54.63 to 147.91 mg·g−1, which were higher than those of COF (15.99–64.06 mg·g−1) and MXene (27.58–33.92 mg·g−1). The adsorption experimental data of adsorption isotherm and kinetics separately followed the Langmuir and pseudo-second-order models. Through density functional theory (DFT), Forcite calculation, UV-Vis and XPS analyses, pore size selectivity, electrostatic and hydrogen bond interactions were determined as the main driving forces for FQs adsorption. Finally, COF@MXene coupled with HPLC-DAD was employed for the analysis of FQs from water, egg and drug samples, and the recoveries were satisfactory. This work reported a covalent assembly synthesis strategy for the preparation of COF@MXene composite for FQs removal. This approach may establish a viable route for gentle fabrication of COF and MXene based composites for various applications.

Lychee peels-derived biochar-supported CaFe2O4 magnetic nanocomposite as an excellent adsorbent for effective removal of nitrate and phosphate from wastewater

In this work, the lychee peels-derived biochar-supported calcium ferrite magnetic nanocomposite (LP-BC@CaFe2O4) was successfully developed and used as an excellent adsorbent for simultaneous removal of nitrate and phosphate from water medium. The adsorption behaviors and mechanisms were studied using property analysis, batch experiments and mathematical model data fitting. The results showed that the LP-BC@CaFe2O4 exhibited the higher removal performance of NO3- and PO43- compared with pristine biochar (LP-BC) by about twice thanks to enrichment of M-OH groups on the LP-BC@CaFe2O4’s surface. The removal of NO3- and PO43- maximized at pH of 6.0 and 5.0, respectively. The adsorption behaviors of NO3- and PO43- were the best described by Sips model with the highest adsorption capacities of NO3- and PO43-, respectively, were 60.3 mg N/g and 57.4 mg P/g. The adsorption kinetic data of NO3- and PO43- were fitted well by Elovich model, suggesting that the adsorption process was chemisorption onto heterogeneous surface. The adsorption mechanisms of NO3- and PO43- on the LP-BC@CaFe2O4 were through electrostatic attraction, surface complexion and ligand exchange. Besides, the surface precipitate participated in removal of PO43-. In addition, the LP-BC@CaFe2O4 had high regeneration and reusability, indicating the LP-BC@CaFe2O4 was a fully promising nanocomposite biochar for effective removal of NO3- and PO43- from water environment.

A Strategy to Valorize a By-Product of Pine Wood (Pinus pinaster) for Copper Removal from Aqueous Solutions.

This study describes the valorization of a pine wood by-product (Pinus pinaster) in the form of individualized fibers to a complex copper or more broadly metals present in an aqueous solution using a batch process. The adsorption results show that pine fibres activated by sodium carbonate are effective in recovering copper ions from monocontaminated or polycontaminated solutions of varying concentrations in a few minutes. One gram of material captures 2.5 mg of copper present in 100 mL of solution at pH 5 in less than 10 min. The results are perfectly reproducible and independent of pH between 3 and 5. The presence of the Na+ cation at concentrations of 0.1 M has no impact on material performance, unlike that of Ca2+ ions, which competes with Cu2+ ions for active sites. The adsorption process can be considered as rapid, as most of the copper is adsorbed within the first 10 min of exposure. Investigation of modeling possibilities shows some limitations. Indeed, the Weber and Morris and Elovich models show poor possibilities to describe all the kinetic data for copper adsorption on fibres. This may prove that the mechanism is far more complex than simple physisorption, chemisorption and/or diffusion. Complexation by wood fibers can be extended to solutions containing several types of metals. The results of this study show that the field of selective metal recovery could be a new way of valorizing by-products from the wood industry.