Isothermal Adsorption Process Research Articles

Adsorption Characteristics of Iron on Different Layered Loess Soils.

In view of the problem of Fe3+ pollution in an iron sulfur mine, different layers of loess soil in the Bijie area were used for adsorption to alleviate the mine wastewater pollution by natural treatment. The effects of the initial concentration of Fe3+, adsorption time and pH value on the adsorption performance of top, core and subsoil layers of loess soils were studied by the oscillatory equilibrium method, and the adsorption mechanism of these three soils was analyzed through a kinetic adsorption experiment and infrared spectroscopy. The results showed that the adsorption capacity of Fe3+ was improved by increasing the initial concentration and reaction time, but the adsorption rate of the adsorption capacity of Fe3+ was reduced. The adsorption rate of Fe3+ in the subsoil layer was faster than that in the other two layers. The higher the pH, the higher the adsorption capacity. After the pH was higher than 3.06, it had little effect on the adsorption capacity, but the adsorption rate increased. The first-order kinetic equation, second-order kinetic equation and Elovich equation were suitable for iron adsorption kinetics of three soils. The fitting correlation coefficient of the second-order kinetic equation was close to one, indicating the main role of chemical adsorption. The adsorption rate constant of the subsoil layer was about two times and three times that of the core soil layer and the topsoil layer. The Langmuir model can better fit the isothermal adsorption process. The results of infrared spectroscopy of soil showed that the content of soil organic matter played an important role in the adsorption capacity of Fe3+. The subsoil layer had a higher concentration of organic matter and more abundant functional groups, so the adsorption capacity of Fe3+ was the highest. The results could provide a theoretical basis for the removal of iron in acid mine wastewater.

Preparation and dynamic moisture adsorption of fiber felt/silica aerogel composites with ultra-low moisture adsorption rate

Understanding the effects of preparation parameters on thermal insulation materials is important for reducing building energy consumption. In this study, fiber felt/silica aerogel composites with ultra-low moisture adsorption rate were prepared by the sol–gel and atmospheric drying technology. The effects of relative humidity and preparation parameters (e.g., silica sol ratios, volume ratios of the sol to fiber felt, aging duration, and modification duration) on the performance (thermal conductivity and moisture adsorption rates) of silica aerogel composites were explored. Furthermore, an isothermal adsorption model of silica aerogel composites for water vapor was established. The results showed in the environment with high relative humidity of 90 %, the moisture adsorption rate and thermal conductivity of the composites were approximately 1 % and 0.02 W·m−1·K−1, respectively. However, the moisture adsorption rate and thermal conductivity of the fiber felt were up to 20 % and 0.1687 W·m−1·K−1, respectively. With the change in the sol ratio, the moisture adsorption rate of the composites varied between 0.7 % and 0.8 % after reaching the adsorption equilibrium. The isothermal adsorption process was described by the D–A isothermal adsorption equation with the correlation of more than 0.99. The prepared fiber felt/silica aerogel composites with ultra-low moisture adsorption rate can be widely used for building insulation, especially in humid areas. This study provides the theoretical data reference for applying new aerogel composites insulation materials in high-humidity environments.

Adsorptive removal of Cu(II) from aqueous solution by fermented sweet sorghum residues as a novel biosorbent

Sweet sorghum straw is a kind of natural wood cellulose with high porosity and high specific surface, which is theoretically conducive to the physical adsorption of heavy metal ions. In this paper, we reported a new biosorbent, the fermented sweet sorghum residues (FSSR), which is a byproduct of bioethanol production by fermentation of sweet sorghum straw, for the removal of Cu(II) from aqueous solution. The properties of the adsorption of Cu(II) on SSR and FSSR were studied and compared. The adsorption process of Cu(II) by SSR and FSSR conformed to the Elovich kinetic model. The isothermal adsorption process conformed to the Freundlich and the Tempkin models. The adsorption capacity of FSSR for Cu(II) was increased with the increase of pH. The adsorption mechanism of Cu(II) by FSSR was mainly attributed to ion exchange. SSR and FSSR were characterized by SEM-EDS, FTIR and XRD. The surface of FSSR had microporous structure, the content of –OH and other active functional groups increased. The fermentation has a certain destructive effect on the crystal structure of cellulose with the increase of amorphous structure. Therefore, fermentation process could be regarded as an effective means of microbial modification, to destroy the structure of the straw and result in the porous structure, which improved the adsorption capacity of SSR for heavy metals. FSSR could be used as a potential biosorbent for heavy metal removal from aqueous solution. Ethanol fermentation might be an effective method to improve performance of biosorbent for Cu adsorption.

Gadolinium metal-organic frameworks realizing ultra-high adsorption capacity toward anionic dyes in aqueous solution

With the development of various industries, the impact of organic dye wastewater discharge on the environment cannot be ignored. Adsorbents and their adsorption properties are the key to the removal of organic dyes from wastewater. In this study, gadolinium metal organic frameworks (Gd-BDC, Gd-BDC-NH2) were synthesized for the adsorption of anionic dyes in water and exhibited excellent adsorption performance, particularly in Congo red (CR) up to 4592.3 and 5507.1 ​mg ​g−1 at room temperature, respectively. The kinetics simulation showed that the adsorption process was more consistent with the pseudo-second-order model; while the Freundlich model is more suitable to describe the isothermal adsorption process of Gd-MOFs. The electrostatic interaction, π-π stacking and hydrogen bonding between the anionic dye CR and the cationic material Gd-MOFs are the main reasons for the ultra-high adsorption of CR. The excellent adsorption performance on anionic dyes indicates that it is a promising high-performance adsorbent.

Tetracycline adsorption trajectories on aged polystyrene in a simulated aquatic environment: A mechanistic investigation

Microplastics (MPs) have attracted widespread attention as an organic class of pollutants as well as pollutant carriers in recipient aquatic ecosystems. In this study, tetracycline (TC) adsorption by polystyrene (PS), with multiple aging-based temporal changes in the adsorption mechanism, was observed. The results revealed that the pseudo-second-order model accurately predicted the TC adsorption kinetics for different types of PS. In addition, the isothermal adsorption processes fit the Freundlich model; however, their interactions were drastically weakened at lower temperatures or increasing salinities. Corresponding to the electrostatic interactions, adsorption TC was largely pH-dependent, with the maximum adsorbed TC content on the PS surface at a pH of 5 in an aqueous environment. More importantly, mechanistic studies have revealed that, compared to virgin PS, TC complexes with aged PS are principally controlled by hydrogen bonding and ionic interactions, followed by π–π, polar-polar, and van der Waals interactions. These findings will aid in understanding the insights of TC and aged PS interactions and the underlying interactive molecular forces, which will be advantageous for comprehending the real case scenario of inter-pollutant interactions and related environmental pollution.

Decolorization of xylose mother liquor with polydivinylbenzene/aminated polyglycidyl methacrylate interpenetrating polymer networks

ABSTRACT An interpenetrating polymer network originating from the physical entanglement of polydivinylbenzene and aminated polyglycidyl methacrylate (PDVB/PMATAM resin) was prepared for the decolorization of xylose mother liquor, and its adsorption performance and mechanism were explored. The resin had a good decolorization effect on the xylose mother liquor, and the decolorization of xylose mother liquor over the resin was completed within a short time due to the synergic effect of hydrophobicity and hydrophilicity. The resin tended to absorb phenols in comparison to sugar, resulting in a high removal rate of phenols and a low loss rate of sugar for xylose mother liquor. The adsorption of pigment impurities on the resin could be described well by a pseudo-second-order model, and its isothermal adsorption process followed Langmuir model. The isosteric adsorption enthalpy of the resin decreased with increasing the fractional loading of pigment impurities, and the distribution of adsorption site on the resin was inhomogeneous. The saturation adsorption capacity of pigment impurities in the fixed-bed column packed by the resin reached up to 14 times of the resin volume, and the reusability of the resin basically remained constant, which shows a good application prospect.

Strontium-doped hydroxyapatite as adsorbent effectively to remove lead ions from water.

In this study, a strontium-doped hydroxyapatite (Sr-HAP) was synthesized by the solgel method, which was used as adsorbent to remove lead ions (Pb2+) from water. The results showed that the adsorption capacities of the Sr-HAP were obviously higher than those of the HAP, the adsorption capacities of which for Pb2+ reached 651.175mg/g. The proper increasement in the dosage of adsorbent was beneficial to the removal of Pb2+ by Sr-HAP. Meanwhile Sr-HAP had a wide applicable pH range for Pb2+. And the increasement in temperature could increase the adsorption capacity of Sr-HAP for Pb2+ to a certain extent. The Langmuir model was used to fit the isotherm adsorption process of Sr-HAP to Pb2+ in water. Compared with HAP, the specific surface area of Sr-HAP has increased by 11.1%, and the pore size distribution of Sr-HAP tended to be smaller and more uniform. Hence, Sr-HAP could be used as an ideal adsorbent to remove Pb2+ in wastewater.

Magnetic molecularly imprinted polymers for selectively adsorbing flavins and their effects on bioremoval of Acid Red 18 and Cr(VI)

AbstractBACKGROUNDFlavins can be used as redox mediators to accelerate anaerobic biotransformation of refractory pollutants. For better application of flavins, suitable immobilization methods need to be developed. As most microorganisms can synthesize flavins, it is a good strategy to develop selective solid sorbents for immobilizing the flavins released by waste biomass including waste activated sludge (WAS).RESULTSNovel core–shell magnetic molecularly imprinted polymers (MMIPs) for flavins were successfully prepared. The adsorption amount of 10 mg of MMIPs for flavin mononucleotide (FMN) could reach 29.19 μmol g−1, which was around 24.9‐fold higher than that of magnetic non‐molecularly imprinted polymers (1.17 μmol g−1). Their isothermal adsorption process followed the Langmuir model. Similar adsorption behaviors of MMIPs were also observed for flavin adenine dinucleotide (FAD) and riboflavin. The three flavins adsorbed on MMIPs enhanced the removal rates of azo dye Acid Red 18 (AR 18) and Cr(VI) by Shewanella oneidensis MR‐1. Moreover, the catalytic performance of MMIPs–FMN could remain at 97.6% of the original value after five repeated usages. Further studies found that MMIPs could efficiently adsorb FAD from the lysate of WAS, and MMIPs–FAD enhanced the decolorization of AR 18.CONCLUSIONSThe novel MMIPs could selectively adsorb flavins. MMIPs–flavins exhibited good catalytic and repeated usage performances, indicating that they could be used for accelerating anaerobic biotransformation of refractory pollutants. © 2022 Society of Chemical Industry (SCI).

Efficient adsorption separation of succinic acid with a novel resin derived from styrene/methyl acrylate/vinyl acetate terpolymer

A novel resin arising from the styrene/methyl acrylate/vinyl acetate (SMVA) terpolymer was prepared for efficient separation of succinic acid with hot water as an eluent, and its separation performance and mechanism were studied. Results indicated the SMVA resin exhibited a better performance on the adsorption of succinic acid with a short time for reaching the equilibrium. The adsorption process of succinic acid on the resin was exothermic and could be described by a pseudo-second-order model, and its isothermal adsorption process followed the Freundlich model. The surface of the resin was inhomogeneous, and the hydrogen bond played a positive role in promoting the adsorption of succinic acid on the resin. The adsorption capacity of succinic acid on the resin was sensitive to pH value, and better adsorption capacity was obtained at pH value between 2 and 3. The pure succinic and acetic acids in a fixed-bed packed by the resin was obtained with the definite time-period collection strategy, and the resolution of components reached to 0.82. The recovery rates of pure succinic and acetic acids on the resin basically remained constant, which shows a better application prospect.

Effect of high-temperature treatment on the desorption efficiency of gas in coalbed methane reservoirs: Implication for formation heat treatment

Formation heat treatment has been considered as a potential stimulation technology for the enhanced recovery of coalbed methane. However, the influence of heat treatment on the desorption efficiency of coalbed methane has not been clarified. In this study, isothermal adsorption experiments of a cylindrical anthracite coal treated at 25 °C, 200 °C, 400 °C, 600 °C, and 800 °C were conducted to investigate the variation in the methane adsorption potential and desorption efficiency. The pore structure of coal was characterized by nuclear magnetic resonance measurements and scanning electron microscopy. Changes in the organic matter and functional group content of coal were monitored by proximate analysis and Fourier transform infrared spectroscopy. Results reveal that pore structure and composition are the main factors that affect the coal adsorption potential. With the increase in the temperature to 200–600 °C, the maximum adsorption potential of coal increased by 7% due to the increase in the pore volume and the functional group content. At a heat-treatment temperature of 800 °C, the functional group content decreased, which in turn reduced the maximum adsorption potential by 76%. Comparison of isothermal adsorption data of coals with different ranks reveals that the Langmuir parameter of bituminous coals is more easily affected by heat treatment in comparison with that of anthracite coal. Based on the reversible theory of coalbed methane isothermal adsorption and desorption process, weighted pressure was proposed, which could comprehensively evaluate the desorption efficiency of coal after heat treatment at different temperatures, and the heat treatment temperature for the optimal desorption efficiency can be determined by the weighted pressure.

Efficient treatment of lead-containing wastewater using bagasse biochar modified via hydroxylapatite

A hydroxylapatite bagasse biochar composite was prepared via the hydrothermal chemical precipitation method with bagasse as the primary raw material. The adsorption capacity of hydroxylapatite bagasse biochar composite for Pb(II) was determined using a series of batch adsorption experiments. The results showed that the point of zero charge value was near neutral pH, and the optimal pH ranged from 4.0 to 7.0. Langmuir isotherms were suitable for fitting the isothermal adsorption process of Pb(II) by the hydroxylapatite bagasse biochar composite. The maximum adsorption capacity of hydroxylapatite bagasse biochar composite in terms of Pb(II) was 210 mg·g-1 at 25 °C. Fourier transform infrared spectrometry analysis indicated that oxygen-containing functional groups were abundant on the external and internal surfaces of the composite sample, which provided numerous chemical sorption sites and resulted in an increase in the adsorption capacity of the composite sample. The Pb(II) removal mechanism of the hydroxylapatite bagasse biochar composite primarily utilized surface diffusion, electrostatic attraction, surface complexation, ion exchange, and a dissolving-coprecipitation reaction. The composite sample was suitable for the treatment of lead-contaminated water (containing zinc, arsenic, cadmium, etc.), which was a promising environmentally friendly material.

Functionalized Activated Carbon Fibers by Hydrogen Peroxide and Polydopamine for Efficient Trace Lead Removal from Drinking Water.

To achieve efficient and selective trace heavy metals removal from drinking water, a low-cost purification material polydopamine/activated carbon fibers (PDA/H-ACF) was successfully prepared by polymerizing dopamine on the surface of activated carbon fibers pretreated with hydrogen peroxide. The morphology, phase, surface functional groups, specific surface, and pore size distribution of the as-prepared sample were analyzed using FESEM, XPS, BET and pore size distribution test (PST), and FTIR, and orthogonal experiments were used to investigate the influences of concentration of H2O2, pretreatment time, and reflux temperature on trace lead removal. The results showed that the sample pretreated under optimized conditions could produce different pore structures, and the content of functional group -COOH obviously increased. After further modification by polydopamine, the contents of -NH-, -NH2, and -OH functional groups on the surface obviously enhanced, which were beneficial to increase adsorption site and promote trace lead removal. The effluent lead concentration decreased from initial 150 to 3.18 ppb within 5 min, meeting the requirement of NSF International Standard/American National Standard for Drinking Water Treatment Units (NSF/ANSI 53-2020) (5 ppb). The isothermal adsorption process and adsorption kinetics could be well-fitted by the Langmuir isotherm and pseudo-second-order kinetics model, indicating that the adsorption process of trace lead by PDA/H-ACF belonged to monolayer and chemical adsorption. Moreover, the as-prepared PDA/H-ACF also showed superior trace lead adsorption performance in the presence of high concentration competitive metal ions, in a wide pH range and in tap water, and therefore had good application prospect in the field of drinking water purification.

Activation mechanisms of apatite by purifying reagent polyacrylamide for backwater from mineral processing in flotation of rare earths

This study revealed activation mechanisms of apatite by polyacrylamide (PAM) during flotation of rare earth minerals in Bayan Obo Ore. This activation leads to high phosphorus content in rare earth concentrate. Ultraviolet (UV) absorption measurements show that adsorption of PAM on the surfaces of apatite and rare earths follows a pseudo-second-order reaction kinetic model. The isothermal adsorption process follows the Freundlich adsorption model, indicating that the adsorption of PAM on apatite is a multi-layer, non-uniform process, that is, physical and chemical adsorption occurs simultaneously. The measured zeta potential shows that under weakly alkaline conditions, amide groups with a negative charge are adsorbed on the surface of apatite, increasing the electronegativity, so that the potential is shifted negatively; however, the negative shift of the potential on the surface of rare earths is insignificant. Fourier transform infrared (FT-IR) test and X-ray photoelectron spectroscopy (XPS) results imply that PAM is chemically adsorbed on the surface of apatite, while 506E undergoes stronger chemical adsorption than PAM on the surface of rare earth minerals. It is found that multi-layer, non-uniform adsorption of PAM combining physical and chemical adsorption occurs on the surface of apatite and the process is dominated by physical adsorption: the adsorption of PAM on surfaces of apatite is stronger than that on the surface of rare earth minerals. Such adsorption activates the apatite, causing it to float during the flotation of rare earths, which is the reason for the high phosphorus content in the rare earth concentrate.

Preparation and characteristic of high surface area lignin-based porous carbon by potassium tartrate activation

In order to study the property of lignin-based porous carbon activated by potassium tartrate, the effects of activator types, activator/lignin mass ratio and activation temperature on the surface morphology, specific surface area and pore size distribution of alkali lignin based porous carbon materials were systematically investigated. Meanwhile, the methyl orange adsorption capacity and adsorption kinetics of the lignin-based porous carbon were also evaluated. The N2 adsorption-desorption experiment results showed that the specific surface area value of lignin-based porous carbon materials activated by potassium tartrate (APC-J), KOH (APC-K), and NaOH (APC-Na) are 947, 1113 and 762 m2/g, respectively. Meanwhile, APC-J has a special microporous structure, while the pore structures of APC-K and APC-Na are mainly mesopores. The best specific surface area of lignin-based porous carbon materials was 1911 m2/g obtaining from APC-J-2-8 sample (mass ratio 2:1, activation temperature 800 °C). The adsorption experiment of methyl orange (MO) showed that the adsorption kinetics of APC-J-2-8 conformed to the quasi-second-order kinetic model, mainly chemical adsorption. The isothermal adsorption process conforms to the Langmuir adsorption isothermal adsorption model, which is a single molecular layer adsorption, and the maximum adsorption amounts are 526.31 mg/g.

Performance and mechanisms of fly ash for graphene oxide removal from aqueous solution.

The potential wide use of graphene oxide in various fields results in the possibility of its dispersion throughout natural water systems, with a negative impact on organisms and ecosystems. This study evaluated the removal of graphene oxide (GO) from water by fly ash (FA). The effects of various conditions (including the initial concentration of graphene oxide, the pH of the initial solution, the amount of absorbent, and temperature) on the removal rate of GO were investigated in detail. The results show that the maximum removal rate of graphene oxide by fly ash is 93%; the isotherm adsorption process conforms to a Langmuir model; the adsorption reaction is a spontaneous exothermic process. Under optimal conditions, the pH of the solution was adjusted to 6, the amount of fly ash was 5 mg, the initial concentration of GO was 60 mg·L-1, and the temperature was 303 K. Using X-ray diffraction (XRD), Raman spectroscopy (Raman), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM), Zeta potential and X-ray electron spectroscopy (XPS), the adsorption mechanism was characterized. The experimental results demonstrate that fly ash is a good material for GO removal from aqueous solution.

Preparation and adsorption properties of Ni(ii) ion-imprinted polymers based on synthesized novel functional monomer

Abstract In this study, a novel functional monomer N-(1-(2,4-difluorophenyl)-2-(1H-1,2,4-triazol-1-yl)ethyl)acrylamide (NDTEA) was designed and synthesized, and was used to prepare Ni(ii) ion-imprinted polymers (Ni(ii)-IIPs). Sixteen kinds of Ni(ii)-IIP (Ni(ii)-IIP1–16) and corresponding non-imprinted polymers (NIP1–16) were prepared by precipitation polymerization method. After optimized condition experiment, Ni(ii)-IIP5 possessed maximum adsorption capacity and better imprinting factor under optimal experimental conditions which indicated by equilibrium adsorption experiments. The morphology and structural characteristics of Ni(ii)-IIP5 were characterized by scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET). The adsorption selectivity of Ni(ii)-IIP5 was analyzed by ICP-OES, and the results showed that Ni(ii)-IIP5 had favorable selectivity recognition ability for Ni(ii) when Cu(ii), Co(ii), and Cd(ii) are used as competitive ions. The kinetic experiment indicated that the performance of Ni(ii) adsorption on the surface of Ni(ii)-IIP5 obeyed the pseudo-first-order model, and adsorption equilibrium was attained after 15 min. Isothermal adsorption process fitted to Langmuir and Freundlich isothermal adsorption models, simultaneously. The results showed that Ni(ii)-IIP5 prepared by using a new functional monomer had better permeation selectivity and higher affinity for Ni(ii), which also verified the rationality of the functional monomer design. At the same time, it also provided a broad application prospect for removal of Ni(ii) in complex samples.

Investigation of the Adsorption of Sulfamethoxazole by Degradable Microplastics Artificially Aged by Chemical Oxidation.

In this study, three different types of microplastics were aged by the thermal activation K2S2O8 method to investigate the adsorption behavior for sulfamethoxazole (SMX) in aqueous solution. The effects of pH, salinity and humic acid (HA) on adsorption behavior were also investigated. At the same time, the morphology and functional groups of microplastics before and after adsorption were characterized. As the aging time increased, the adsorption capacity of the microplastics also increased significantly. Whether it was pristine or aged, polylactic acid (PLA) had the highest adsorption capacity. The adsorption capacity of microplastics was the largest under acidic conditions, and its adsorption capacity decreased significantly in alkaline solutions. The presence of salinity inhibited the adsorption of SMX on polyethylene terephthalate (PET) and PP, but the adsorption capacity of PLA increases when salinity was above 10‰. The adsorption of SMX on microplastics was promoted by HA. When the concentration of HA was 20mg/L, the adsorption capacity of PLA and PET decreased. Kinetic and isotherm fits were applied to the adsorption process. The increase in sorption capacity was related to the development of holes and cracks and the enhanced number of surface oxygen-containing functional groups. The adsorption kinetics to pristine microplastics conformed to a pseudo-first-order kinetic model, while the kinetics of the aged microplastics conformed to a pseudo-second-order kinetic model. It implies that the adsorption of SMX by aging microplastics involves multiple processes. The adsorption isothermal adsorption process of SMX by microplastics accorded with Freundlich model, belonging to multi-layer adsorption.

Effects of tall fescue biochar on the adsorption behavior of desethyl-atrazine in different types of soil

Desethyl-atrazine (DEA) is a metabolite of atrazine that exerts a considerable influence on the environment. In this study, tall fescue biochar was prepared by pyrolysis at 500 °C, and batch experiments were conducted to explore its effect on the adsorption behavior of DEA in red soil, brown soil, and black soil. The addition of biochar increased the equilibrium amount of DEA adsorption for the three soil types. A pseudo-second-order kinetic model most closely fit the DEA adsorption kinetics of the three soils with and without biochar, with a determination coefficient (R2) of 0.962 to 0.999. The isothermal DEA adsorption process of soils with and without biochar was optimally described by the Freundlich and Langmuir isothermal adsorption models with R2 values of 0.98 and above. The DEA adsorption process in the pristine soil involved an exothermic reaction, which became an endothermic reaction after the addition of biochar. Partitioning was dominant throughout the entire DEA adsorption process of the three pristine soils. Conversely, in soils with biochar, surface adsorption represented a greater contribution toward DEA adsorption under conditions of low equilibrium concentration. The overall results revealed that the tall fescue biochar was an effective adsorbent for DEA polluted soil.

Effective adsorption of quadrivalent cerium by synthesized laurylsulfonate green rust in a central composite design

The layered laurylsulfonate intercalated green rust (lauryl-S GR) was synthesized to evaluate the influence of synthesis parameters and aqueous conditions on the adsorption of CeIV. The maximum adsorption capacity of 305.58 mg/g by lauryl-S GR was predictably obtained. The pseudo-first-order kinetic model was appropriate in fitting the whole uptake process in a weak acid environment. Three isotherm models including Langmuir, Freundlich, and Tempkin were all reliable in depicting the isotherm adsorption process. The maximum monolayer adsorption capacity of lauryl-S GR towards CeIV was 315.46 mg/g. Ce species including CeO and Ce2O3 besides CeO2 were matched in the XPS distribution, directly indicating the reduction reaction brought by FeII in the GR occurred to hydrated CeIV ions during the adsorption. Nano-sized Ce particles attached to the lauryl-S GRs after the adsorption experiments were observed in the morphological characterization. Flocculated materials were formed on the surface of the lauryl-S GR at a pH of 7, which further reduced the active sites and disrupted the continuous uptake of CeIV to the lauryl-S GR. This study expands the application of GRs and supplies an ideal iron-based material for the construction of the affiliated recovery pathway to the traditional separation of Ce.

Utilization of Jujube Biomass to Prepare Biochar by Pyrolysis and Activation: Characterization, Adsorption Characteristics, and Mechanisms for Nitrogen.

The rapid advancement of jujube industry has produced a large amount of jujube biomass waste, requiring the development of new methods for utilization of jujube resources. Herein, medium-temperature pyrolysis is employed to produce carbon materials from jujube waste in an oxygen-free environment. Ten types of jujube biochar (JB) are prepared by modifying different pyrolysis parameters, followed by physical activation. The physicochemical properties of JB are systematically characterized, and the adsorption characteristics of JB for NO3− and NH4+ are evaluated via batch adsorption experiments. Furthermore, the pyrolysis and adsorption mechanisms are discussed. The results indicate that the C content, pH, and specific surface area of JB increase with an increase in the pyrolysis temperature from 300 °C to 700 °C, whereas the O and N contents, yield, zeta potential, and total functional groups of JB decrease gradually. The pyrolysis temperature more significantly effects the biochar properties than pyrolysis time. JB affords the highest adsorption capacity for NO3− (21.17 mg·g−1) and NH4+ (30.57 mg·g−1) at 600 °C in 2 h. The Langmuir and pseudo-second-order models suitably describe the isothermal and kinetic adsorption processes, respectively. The NO3− and NH4+ adsorption mechanisms of JB may include surface adsorption, intraparticle diffusion, electrostatic interaction, and ion exchange. In addition, π–π interaction and surface complexation may also be involved in NH4+ adsorption. The pyrolysis mechanism comprises the combination of hemicellulose, cellulose, and lignin decomposition involving three stages. This study is expected to provide a theoretical and practical basis for the efficient utilization of jujube biomass to develop eco-friendly biochar and nitrogenous wastewater pollution prevention.