Experimental Adsorption Isotherms Research Articles

Monolayer magnetic nanospheres have selective binding that allow the concentration of low-abundance proteins from blood serum

Here, the efficiency of magnetic nanosphere (Fe3O4) coated with L-histidine (L-his) was evaluated to enrich proteins of low-abundance in human serum. The chemometric analysis provided optimal conditions to concentrate low-abundance proteins, reducing the dynamic range of protein levels in the serum sample. Three independent factors (temperature, mass ratio and pH) were tested. The optimal condition achieved was using temperature (42 °C), ratio (3:1, nanomaterial/sample) and pH (5.5). The kinetic study revealed that the adsorption of proteins on the surface of the monolayer magnetic nanosphere follows a pseudo-second order model with R2 = 0.9153. Adsorption isotherm experiments revealed high capacity of protein adsorption on the surface of the nanosphere, indicating a maximum theoretical adsorption capacity (qmax) of 123.45 mg g−1. The efficiency of enrichment of low-abundance proteins in the serum sample was evaluated by gel electrophoresis (SDS-PAGE). Furthermore, when compared to the method using organic solvent (acetonitrile), Fe3O4@L-his showed adequate efficiency to simplify the serum sample. Using MALDI-TOF/TOF, approximately 50 proteins were identified using Fe3O4@L-his. As a proof of concept for this study, patients with bipolar disorder and healthy controls were discriminated using the magnetic nanosphere as an adsorbent in the sample preparation step. These results show that Fe3O4@L-his can be a fast, robust, and simple alternative to enrich low-abundance proteins in human serum, emerging as an important strategy in the search for biomarkers of human diseases.

Optimization of Mixed-Based Biochar Preparation Process and Adsorption Performance of Lead and Cadmium

Irreversible pollution by heavy metals such as lead (Pb) and cadmium (Cd) adversely affects the ecological environment and human health. Due to its high adsorption, microporosity, and specific surface area, biochar possesses excellent potential for use in heavy metal pollution remediation. The preparation of mixed-based biochar from sludge and cotton stalk can solve the problems inherent to pure sludge biochar, such as undeveloped pore structure and a small specific surface area, while resourcefully utilizing both waste biomass types. This study investigated the adsorption capacity for Pb2+ and Cd2+ of mixed-based biochar prepared at different pyrolysis temperatures, different pyrolysis residence times, and different cotton stalks percentages. Response surface experiments revealed the optimum process conditions for preparing mixed-based biochar, which included a pyrolysis temperature of 638 °C, a pyrolysis residence time of 86 min, and an addition ratio of 50% for cotton stalks. The isothermal adsorption experiments revealed that the maximum adsorption capacities of mixed-based biochar for Pb2+ and Cd2+ were 111.11 and 86.21 mg/g, respectively. Our findings suggest the co-pyrolysis of sludge and cotton stalk as a green and sustainable method for safely disposing of Pb and Cd.

Thermodynamic behavior of water vapor adsorption in shale and its dependence on organic matter and clay minerals

Isothermal adsorption experiments of water vapor in shale samples with differing TOC (total organic carbon content) and differing clay content were conducted at three set temperatures to reveal the adsorption mechanism, and to determine the thermodynamic dependence of primary and secondary adsorption processes on the content of organic matter and clay minerals. The adsorption of water vapor in shale is spontaneous with the Gibbs free energy change is minus ranging from −0.28 - −5.15 KJ/mol, the adsorption changes from entropy driven to enthalpy driven as the adsorption amount increases (enthalpy change turns from plus to minus ranging from −1.25–––6.72 KJ/mol, and the entropy change is opposite ranging from −0.0031–––0.035 KJ/mol), and the primary adsorption amount increases with higher experimental temperature but secondary adsorption amount decreases. Fitting results and their relying theories indicate that micropore filling and monolayer adsorption occur in primary adsorption mainly though strong hydrogen bonding and electrostatic forces between water vapor and the pore surface, and multilayer adsorption and capillary condensation dominate secondary adsorption mainly through weak hydrogen bonding among water vapor. There are positive correlations of adsorption amount versus both clay content and TOC. Clay minerals are strongly hydrophilic because of their exchangeable cations and polar groups, providing primary and secondary adsorption sites, and enhancing the spontaneity of adsorption. OFGs (oxygen functional groups) in organic matter are hydrophilic, other pore surfaces are hydrophobic or weak hydrophilic, which also develop many adsorption sites. Results from this work provide new insights about the influence of organic matter and clay minerals on the adsorption thermodynamic behavior of water vapor in shale.

Highly selective and reusable nanoadsorbent based on expansive clay-incorporated polymeric nanofibers for cationic dye adsorption in single and binary systems

Fabrication of nanoadsorbents with excellent adsorption capacity, selectivity, easy separation, and superior reusability for removing organic dyes from polluted water remains challenging. In this study, novel expansive clay/polyvinyl alcohol nanofibers (clay/PVA NFs) were fabricated as sheet-membranes using an electrospinning technique. The expansive clay with different ratios (5, 10, and 15 wt%) was incorporated into PVA NFs and comprehensively studied in terms of morphological and physicochemical characteristics. SEM images showed that incorporating the clay by electrospinning resulted in nanofibers with smaller diameters than the neat PVA NFs. The clay/PVA composite possesses high stability in aqueous media and a negatively charged surface at a pH higher than 4.1. The results showed that incorporating clay into PVA NFs improved the adsorption capacity for removal of crystal violet dye (CV) from single and binary systems. The incorporation of 5 % clay into the PVA NFs reduced diameter from 341 to 217 nm and increased its maximum adsorption capacity for the CV dye removal from 48.65 to 121.73 mg/g. The Redlich-Peterson and pseudo-first order models provided the best modeling of the experimental adsorption isotherm and adsorption kinetic data, respectively. The clay/PVA NFs exhibited outstanding reusability, with a removal efficiency for CV dye of 99.34 % after ten cycles of reuse with easily separated after adsorption. In addition, the clay/PVA NFs have good selectivity for separating CV dye from various binary dye systems. The selectivity of the clay/PVA to separate the CV dye from the binary dye systems of CV/methylene blue, CV/Coomassie brilliant blue, and CV /hematoxylin was 88.57 %, 90.92 %, and 97.24 %, respectively. Finally, excellent adsorption performance, good selectivity, high reusability, and ease of separation make clay/PVA NFs a promising adsorbent for CV dye removal from complex wastewater.

Unravelling the complex adsorption behavior of extracellular polymeric substances onto pristine and UV-aged microplastics using two-dimensional correlation spectroscopy

In this study, we examined the preferential adsorption behavior of extracellular polymeric substances (EPS) on two commonly used microplastics (MPs), including polyethylene (PE) and polypropylene (PP), through adsorption kinetics and isotherm experiments. The effects of UV aging on EPS adsorption were also explored. The results showed that EPS adsorption was greater on UV-aged MPs than on pristine MPs, with an adsorption capacity of approximately 27.0 mg-C/m2 for aged PP-MPs and 23.5 mg-C/m2 for pristine PP-MPs, and 16.4 mg-C/m2 for aged PE-MPs and 12.5 mg-C/m2 for pristine PE-MPs. Fourier transform infrared (FTIR) spectra revealed that EPS adsorption was governed by hydrogen bonds between EPS molecules and methylene groups in pristine MPs and CO, C–O groups in UV-aged MPs, as evidenced by the addition and the reduction of the related peaks shown in MP surfaces and residual EPS after adsorption, respectively. Fluorescence spectroscopy revealed that protein-like components exhibited higher Freundlich adsorption affinity (i.e., Kf), ranging from 0.34 to 1.29 (RU⋅L m−2) (RU⋅L−1)n than humic-like components (0.01 to 0.12 (RU⋅L m−2) (RU⋅L−1)n). The EPS molecular distribution was consistent with the FTIR results, showing preferable adsorption of biopolymer versus humic substances fraction. Two-dimensional correlation spectroscopy combined with FTIR (2D-COS-IR) revealed that polysaccharides in EPS were more preferentially adsorbed onto MPs and the order of the sequence was polysaccharides > proteins > humic-like substances for all MPs tested. This study provides new insight into the complex adsorption behavior of heterogeneous EPS on MPs and the associated alterations in the potential environmental fate of MPs.

Investigation of adsorption-diffusion behaviors of elementary O2, CO2, and N2 in coal particles: influence from temperature.

Adsorption-diffusion behaviors of gases (i.e., O2, CO2, and N2) in coal are directly related to the coal spontaneous combustion (CSC), in which the temperature is the key factor affecting the gas migration process in coal. In this work, isothermal adsorption experiments of O2, CO2, and N2 under different temperatures were carried out on bituminous coal and anthracite coal samples at 0.5MPa, respectively. Based on the free gas density gradient diffusion (FDGD) model, the microchannel diffusion coefficients of different gases at different temperatures were calculated, and the effects from temperature were quantitatively evaluated. The results acquired from the experiment and simulation show that (i) the adsorption capacity of these three gases decreases as the temperature increases, and the adsorption capacity at the same temperature satisfies CO2 > O2 > N2; (ii) the FDGD model is verified to be still applicable at different temperatures, indicating that the adsorption-diffusion behavior of O2, CO2, and N2 in coal particles at different temperatures is still consistent with the FDGD diffusion; (iii) the microchannel diffusion coefficient Km of the three gases gradually increases when the temperature goes up. The present work contributes to the understanding of the gases migration process in the development of CSC.

Research on Pore-Fracture Characteristics and Adsorption Performance of Main Coal Seams in Lvjiatuo Coal Mine

Gas prevention and control have always been the focus of coal mine safety. The pore structure characteristics and gas adsorption characteristics of coal seams are the key factors affecting gas adsorption and diffusion in coal seams. Lvjiatuo Mine has the characteristics of a high gas content when it enters deep mining. In order to clarify the influence of the pore-fracture structure characteristics of main coal seams in the research area on coal seam gas adsorption and diffusion, and to study the differences in gas adsorption and diffusion ability in different coal seams, low-temperature nitrogen adsorption (LT-N2GA), high-pressure mercury intrusion (MIP) and computerized tomography (μ-CT) were used as characterization methods, and methane isothermal adsorption experiments were carried out to systematically study the pore structure characteristics of five groups of coal samples, and the pore-fracture structure characteristics and gas adsorption characteristics of each main coal seam were obtained. The results show that: (1) in the LT-N2GA experiment, the adsorption–desorption curves of all coal samples are of type III, and mainly develop cone-shaped pores or wedge-shaped semi-closed pores, with an average pore size of 1.84~4.84 nm, a total pore volume of 0.0010~0.0023 mL/g, a total specific surface area of 0.16~0.24 m2/g, and a fractal dimension D1 of 1.39~1.87 and D2 of 2.44~2.60. The micropores of L12 are more developed, and the mesopores and macropores of L9 are more developed. (2) In the MIP experiment, the porosity of coal samples is 3.79~6.94%. The porosity of L9 is the highest, the macropore ratio is the highest, and the gas diffusion ability is also the strongest. (3) In the μ-CT experiment, the porosity of L8-2 and L12 is 12.12% and 10.41%, the connectivity is 51.22% and 61.59%, and the Df is 2.39 and 2.30, respectively. The fracture of L12 is more developed, the connectivity is better, and the heterogeneity of the pore of L8-2 is higher. (4) In the isothermal adsorption experiment of methane, the gas adsorption capacity basically increases with the increase in the buried depth of the coal seam, and the gas adsorption capacity of the No.12 coal seam is the highest. Based on the pore-fracture structure characteristics and gas adsorption characteristics of the main coal seams in the research area, the gas outburst risk of each coal seam is ranked as follows: No.12 coal seam > No.8 coal seam > No.7 coal seam > No.9 coal seam. The experimental results provide important help for researching the structural characteristics of coal seam pore fractures and preventing gas outbursts during deep coal seam mining.

Assessment of CO2 geological storage capacity based on adsorption isothermal experiments at various temperatures: A case study of No. 3 coal in the Qinshui Basin

Carbon dioxide (CO 2 ) capture, utilization, and storage (CCUS) is an important pathway for China to achieve its “2060 carbon neutrality” strategy. Geological sequestration of CO 2 in deep coals is one of the methods of CCUS. Here, the No. 3 anthracite in the Qinshui Basin was studied using the superposition of each CO 2 geological storage category to construct models for theoretical CO 2 geological storage capacity (TCGSC) assessment, and CO 2 adsorption capacity variation with depth. CO 2 geological storage potential of No. 3 anthracite coal was assessed by integrating the adsorption capacity with the static storage and dissolution capacities. The results show that (1) CO 2 adsorption capacities of XJ and SH coals initially increased with depth, peaked at 47.7 cm 3 /g and 41.5 cm 3 /g around 1000 m, and later decreased with depth. (2) four assessment areas and their geological model parameters were established based on CO 2 phase variation and spatial distribution of coal thickness, (3) the abundance of CO 2 geological storage capacity (ACGSC), which averages 40 cm 3 /g, shows an analogous circularity-sharp distribution, with the high abundance area influenced by depth and coal rank, and (4) the TCGSC and the effective CO 2 geological storage capacity (ECGSC) are 9.72 Gt and 6.54 Gt; the gas subcritical area accounted for 76.41% of the total TCGSC. Although adsorption-related storage capacity accounted for more than 90% of total TCGSC, its proportion, however, decreased with depth. Future CO 2 -ECBM project should focus on high-rank coals in gas subcritical and gas-like supercritical areas. Such research will provide significant reference for assessment of CO 2 geological storage capacity in deep coals.

Isothermal adsorption characteristics of various phases of CO2 and CH4 in different rank coals

ABSTRACT Using the remaining coal seams of closed coal mines for CO2 geological storage can effectively slow down the greenhouse effect and realize the redevelopment and utilization of closed coal mines. The burial depth of coal seams in closed coal mines in China covers an extensive range, and CO2 and CH4 could exist in various phases in the coal. The existing experimental objects for CO2 adsorption in coal are mainly associated with the supercritical and gaseous phases, and a research gap comparison between the CO2 adsorption characteristics in the liquid phase and those of other phases is very obvious. Herein, the isotherm adsorption experiments of CO2 and CH4 in different phases on different rank coal samples are methodically conducted in the pressure range of 0-12MPa. The experimental results indicate that the excess adsorption capacity of gaseous CO2 and CH4 (gas pressure <4MPa) rapidly raises with the growth of the adsorption pressure; however, a significant difference for the case of the medium- and high-pressure stage (>4MPa) is detectable. With the growth of the adsorption pressure, the excess adsorption capacity of the supercritical CH4 gradually reaches the maximum value and then remains stable, where the maximum experimental value is 1.009 mmol/g. While the excess adsorption capacity of CO2 near the critical pressure of liquid and supercritical state rapidly reduces and then tends to be stable. The maximum adsorption capacity is capable of touching 2.096 mmol/g, which is stable around 0.5 mmol/g. The analysis indicates that the change in the excess adsorption amount of CO2 near the critical pressure corresponds to the change in its density. The absolute adsorption capacity of CO2 and CH4 monotonically grows in the pressure range of 0-12MPa, and the absolute adsorption capacity of the same coal sample follows the following order: liquid CO2 > supercritical CO2 > CH4. The maximum adsorption capacity values for these substances in order are 2.493, 2.345, and 1.296 mmol/g. With the growth of the coal rank, the Gibbs free energy, specific surface area, and adsorption capacity of the understudied coal samples exhibit a U-shape relationship as a function of their coal ranks.

Ethylenediamine-Functionalized Graphene Oxide Nanosheets for Modifying Chitosan/Polyvinyl Alcohol Membrane Adsorbents for RB19 Removal from Wastewater

Graphene oxide (GO) was covalently functionalized with ethylenediamine (ED-GO) and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, and field emission scanning electron microscopy techniques. Afterward, ED-GO-embedded chitosan/polyvinyl alcohol membrane adsorbents (CP/ED-GO) were fabricated by incorporating different amounts (0–1 wt %) of ED-GO, and the resultant membrane adsorbents were applied for the adsorption of reactive blue 19 dye (RB19) from water. According to the batch adsorption results, the adsorbent containing 0.25 wt % ED-GO possessed the best performance in RB19 removal. Adsorption of RB19 dye onto the CP/ED-GO-0.25 wt % membrane was also optimized using the response surface methodology. The solution pH, initial dye concentration, and adsorbent mass were selected as independent variables. The dye removal of 95% was achieved under the optimized conditions, close to the experimentally measured value, indicating the reliability of the optimization. Isothermal adsorption experiments revealed that RB19 dye adsorption onto CP, CP/ED-GO-0.25 wt %, and CP/GO-0.25 wt % could be well described by the Freundlich isotherm model. The adsorption kinetic of RB19 dye using CP, CP/ED-GO-0.25 wt %, and CP/GO-0.25 wt % membrane adsorbents followed the pseudo-second-order kinetic pattern. The adsorption capacity values of 333.331, 303.03, and 256.41 mg g–1 were obtained for CP/ED-GO-0.25 wt %, CP, and CP/GO membrane adsorbents, respectively. In summary, the CP/ED-GO-0.25 wt % membrane was found to be a promising adsorbent for wastewater decoloring.

Metal–Organic Frameworks for Water Harvesting: Machine Learning-Based Prediction and Rapid Screening

Atmospheric water harvesting based on metal–organic frameworks (MOFs) is an emerging technology to potentially mitigate water scarcity. Because of the tremendously large number of existing MOFs, it is challenging to find suitable candidates. In this context, a data-driven approach to identify top-performing MOFs represents an important direction. Herein, we develop a machine learning (ML) method to predict water adsorption in MOFs and screen out top-performing MOFs for water harvesting. First, experimental water adsorption isotherms in MOFs are collected and water adsorption properties are extracted. Quantitative structure–property relationships are analyzed in terms of pore structure and framework chemistry, providing task-specific design principles. Then, ML models are trained and interpreted to predict water adsorption properties by using structural and chemical features, as well as operating conditions as descriptors. The transferability of the ML models is validated by out-of-sample predictions in seven newly reported MOFs. Finally, the ML models are applied to screen ∼8000 “Computation-Ready, Experimental” (CoRE) MOFs. Top-performing candidates are identified including 149 MOFs with the maximum adsorption capacity ≥35 mmol/g, 39 MOFs with working capacity ≥10 mmol/g in a relative pressure window 0.1–0.3, and 139 MOFs with working capacity ≥8.7 mmol/g in a relative pressure window 0.6–0.9. The developed ML-based method would advance task-oriented design and rapid discovery of reticular materials for energy and environmental applications.

Synthesizing sulfhydryl-functionalized biochar for effectively removing mercury ions from contaminated water.

Biochar is regarded as an effective adsorbent for heavy metal pollution treatment, and functional optimization is still needed to improve its performance. We created raw biochar (BC and BP) from corn straw and pine sawdust, which were modified to produce sulfhydryl-modified biochar (MBC and MBP). Isothermal adsorption experiments and adsorption kinetics experiments as well as the related model fitting were performed to evaluate the adsorption performance of biochar on Hg(II). According to the results of the Langmuir model fitting, the maximum adsorption capacities of sulfhydryl-modified biochar were 193.05mg/g (MBC) and 178.04mg/g (MBP), respectively, which were approximately 1.6 times higher than the raw biochar. The results showed that adding sulfhydryl groups to biochar can improve its adsorption performance. The prompt effect resulted from the sulfhydryl modification providing additional functional groups and enhanced chemisorption and physical adsorption properties.

Adsorption of antibiotics on montmorillonite and site energy distribution analysis

The migration and transformation of antibiotics requires further study in geochemical settings. In this study, the removal effect of montmorillonite (Mt) on antibiotics was investigated, using the broad-spectrum antibiotics ciprofloxacin (CIP) and erythromycin (ERY) as subjects. The results of adsorption kinetics and adsorption isotherm experiments showed that the generalized Langmuir model describe the adsorption process well, and the adsorption capacity of CIP was higher. The intercalation and adsorption behaviors of CIP and ERY on Mt surface were analyzed by FT-IR, SEM, TEM, XRD and Molecular simulation. In order to analyze the different adsorption capacity of these antibiotics on Mt, the theory of site energy distribution was employed. By fitting the experimental data with the Generalized-Langmuir model, the site energy distribution and average site energy were calculated, which revealed the competitive adsorption mechanism of CIP and ERY on Mt. Moreover, the adsorption of antibiotics on Mt under different pH conditions was studied, and the competitive adsorption results were also demonstrated by the potential energy distribution.

Methane Adsorption in Anthracite Coal under Different Pressures and Temperatures—A Study Combining Isothermal Adsorption and Molecular Simulation

In situ gas content is an important parameter associating coalbed methane, while the influence of pressure and temperature on methane adsorption and desorption still needs to be revealed. In this study, the molecular structure and methane adsorption capacity of anthracite coal collected from Diandong Coalfield (China) were studied based on 13C nuclear magnetic resonance (13C NMR), Fourier transform infrared spectroscopy (FT-IR), and methane isothermal adsorption experiment. The results show that the carbon skeleton of coal sample is mainly composed by aromatic carbon (72%), followed by aliphatic carbon structure (14.2%). Carbons connected to the oxygen atoms contribute 13.7% of the total carbons in coal molecule, and the oxygen atoms are mainly in the form of carbonyl. The 2-dimension structure and 3-dimension molecular structure of coal sample was also reconstructed. The average chemical formula of the coal molecule is C200H133O21N3. The experimental methane adsorption isothermal data of the coal sample under different temperatures shows that with increasing the temperature, the methane adsorption amount at each pressure decreases obviously. At 7 MPa and 20°C, the methane adsorption amount of the coal sample is 28.5 cm3/g. Comparably, at 100°C and 7 MPa, the methane adsorption amount is only 15.9 cm3/g, decreasing by 44%. In mesopores, temperature has stronger influence on methane adsorption under higher pressure than that of lower pressure. On the contrary, in micropores, temperature has weaker effects on methane adsorption at higher pressure than that at lower pressure. The results can be beneficial for understanding methane adsorption characteristics of deep coal.

Impact of Adsorption Swelling and Slippage Effects on Changes in Coal’s Permeability at Different Temperatures

As a critical parameter, coal’s permeability influences the coalbed’s methane (CBM) production efficiency, which, in turn, is affected by a slippage effect, adsorption swelling, and effective stress in the CBM exploitation process. In this paper, an isothermal adsorption experiment under various temperatures, including seepage tests comprising CH4 and He in coal at different temperatures under constant effective stress, was carried out separately. We established a modified Shi&Duruca (S&D) model that considered constant effective stress and a modified adsorption model, in which the effect of excess adsorption capacity and temperature was considered. The results revealed that swelling deformation occurred when coal adsorbed CH4, which would result in the permeability of CH4 being lower than that of He under similar conditions. With an increase in pore pressure, coal’s permeability decreased gradually under the combined effects of slippage and adsorption swelling. Temperature is an important factor that affects the movement and storage of gas. Any change in temperature and pore pressure would result in coal’s permeability being comprehensively affected by thermal expansion, thermal cracking, and adsorption swelling, including the effects of slippage. Thermal expansion and thermal cracking increase coal’s permeability under low pressure and decrease coal’s permeability under high pressure. The modified adsorption model and permeability model could better characterize the adsorption and permeability properties of coal. The calculation results illustrated that the slippage effect and adsorption swelling are two important factors affecting permeability, with its permeability increment sharing a similar change trend with changes in permeability. Under the condition of low pressure, the adsorption swelling effect was dominant, and the contributary rate of the slippage effect on permeability would increase, obviously, with an increase in temperature.

Highly stable and efficient Cr(VI) immobilization from water by adsorption with the La-substituted ferrihydrite as a naturally-occurring geosorbent in soils

Ferrihydrite (Fh) is a vital geosorbent in the natural environment. Here, Fh materials with lanthanum (La) substituted in varied La/La + Fe ratios were synthesized, and these La-Fh materials were investigated in-depth via adsorption kinetic and isothermal experiments to explore their adsorption performance for chromate [Cr(VI)] in soils. Material properties of La-Fh were further characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FTIR), and X-ray photoelectron spectroscopy (XPS). The results clearly indicate that La3+ can be integrated into the Fh lattice, but the increase in La amount substituted into Fh is slowed down when the La/La + Fe ratio reaches to a larger value. Those La3+ cations that fail to become integrated may either get adsorbed or form a phase of La(OH)3 on La-Fh surfaces. We also find that La substitution reduces the specific surface area (SSA) of La-Fh samples but raises their pHpzc, which hampers La-Fh conversion to hematite and thus increases the chemical stability. These changes are related to the La-Fh structure and surface aspects, but they do not negatively affect the Cr(VI) adsorption efficacy, which can be promoted over a wide pH range to an alkaline pH. For instance, the maximum adsorption amount of Cr(VI) by 20%La-Fh is 30.2 mg/g at a near-neutral pH. However, the entire chromate adsorption processes are affected by H2PO4− and humic acid due to their strong affinities for Cr(VI), but almost not influenced by NO3− and Cl−. All the Cr(VI)-Fh reactions are well described by the fitted adsorption Freundlich model and conform to the pseudo-second-order reaction kinetic equation. The mechanisms which enhance La-Fh's adsorption ability for Cr(VI) are governed by chemical interactions, because La substitution can increase the hydroxyl density on Fh surfaces and thus improve the reactivity of La-Fh towards Cr(VI), leading to an evidently enhanced Cr(VI) immobilization onto La-Fh.

Kinetics and Adsorption Isotherm of Strontium on Sugarcane Biochar and Its Application in Polluted Soil

Removal of inorganic soil pollutants (e.g. Sr2+) is considered necessary requirement to protect the environment and public health. So sugarcane bagasse biochar (SCBB) was examined as a biosorbent material for Sr2+. This was done through adsorption Stirred-batch technique including a kinetic experiment, at two concentrations (50 and 150 mg/l) and an adsorption isotherm experiment at five concentrations (20, 50, 100, 150, and 200 mg/l), by using SrCl2·6H2O. Moreover, an examination of the role of SCBB at three dosages (0.5, 1, 2%w/w) in reducing the bioavailability of strontium in polluted soil through pots experiment by using Raphanus sativus. Kinetic data revealed that equilibration time was 3 h and pseudo-second-order model was more represented in data at low and high concentrations where (R2 = 0.999 and R2 = 1), respectively. Thus, chemisorption governed the adsorption process for Sr2+removal by SCBB. Furthermore, Langmuir isotherm model (R2 = 0.99) described the adsorption data better, which indicated that a monolayer type of adsorption plays a vital role in the removal of Sr2+ by SCBB. Pots experiment revealed that SCBB could significantly reduce Sr2+ uptake by Raphanus sativus. The percentages of decrease in the shoot were 5.82, 18.17, and 26.80% for SCBB dosage 0.5, 1 and 2% w/w, respectively. The percentages of decrease in root were 17.20, 36.89, and 53.34% for SCBB dosage 0.5, 1 and 2% w/w, respectively. Specific surface area and surface functional groups of sugarcane bagasse play a vital role in the retention of strontium. Hence, biochar played an important role in the removal of Sr2+ from aqueous solution and reduced its uptake by plants in soil.

Sorption and mobility of cadmium in soil impacted by irrigation waters

Soil contamination by Cd has drawn global attention, while how irrigation waters modulate Cd sorption and mobility in soil remains obscure. We address this by investigating how cropped sandy soil irrigated with different waters altered Cd sorption and mobility using a rhizobox experiment followed by a batch experiment. Maize were planted in the rhizoboxes and irrigated by reclaimed water (RW), livestock wastewater (LW) and deionized water (CK), respectively. The bulk soil sampled from each treatment after 60 days of growth was employed to measure the Cd sorption and mobility using the isothermal adsorption and desorption experiments. The results showed that, in a small rhizobox experiment, the adsorption rate of Cd by the bulk soil in the adsorption phase was much faster than the desorption rate in desorption phase. Irrigation with RW and LW both reduced the Cd adsorption capacity of soil, and the reducing degree brought by LW was more obvious. Cd desorption rate was very low but keep increasing in the desorption stage, and pre-RW irrigation had the potential to increase Cd desorption from soil. Although the results were obtained based on the bulk soil sampled from a rhizobox experiment, our study strongly suggests that the altered Cd adsorption and desorption behavior in the soil caused by the RW and LW irrigation may risk the farmland ecosystem and deserve more concern.

Highly efficient removal of Pb2+ from wastewater by a maleic anhydride modified organic porous adsorbent

Sorption is prominent in low price, high efficiency, availability, and eco-friendliness. Organic porous materials have the characteristics of easy functionalization, diverse structure and stability, and show great potential in adsorption, energy storage, catalysis, and other fields. A mesoporous phenolic resin-type polymer (PRP) was successfully synthesized and modified by solid state reaction with maleic anhydride to prepare adsorbent (called as PRP-MAH) for sorption of Pb2+. The impact of reaction conditions (the pH value, reaction temperature, fresh concentration of solution, ionic strength and reaction time, etc.) was systematically studied. Characterization methods such as SEM, FTIR, and XPS indicated that the synthesized adsorbent PRP-MAH had regular morphology and good stability. The fitting of isothermal adsorption experiment data conforms to Langmuir sorption isotherm, and the sorption capacity reached 366.40mg·g-1 at 308K. The kinetic data were consistent with the quasi-second-order model, which indicated that the chemisorption might play the main role in the sorption process. Thermodynamic research manifested that the sorption of Pb2+ by PRP-MAH was carried out by a spontaneous process at the study temperature. The studies show that PRP-MAH can remove Pb2+ from water solution through ion exchange, electrostatic attraction, and surface complexation.

Pore structure characteristics of different lithofacies of the Longmaxi shale, Western Hunan‐Hubei Region, China: Implications for reservoir quality prediction

Lithofacies and micropore characteristics of shale reservoir directly affect the exploration and development of natural gas. To determine the development potential of shales of the Longmaxi Formation in the Western Hunan‐Hubei Region, the lithofacies types and micropore structure characteristics of the Longmaxi Formation shales have been systematically studied in this paper, based on ordinary thin sections, argon ion polishing–scanning electron microscopy, physical property testing, x‐ray diffraction whole‐rock and clay mineral analysis, isothermal nitrogen, and carbon dioxide adsorptions. According to the principle of ‘laminar structure + total organic carbon (TOC) + mineral composition of felsic, clay, and carbonate minerals’, eight types of shale lithofacies were identified. The effective porosity of the Longmaxi shale ranges from 1.8% to 14.4%, with a peak range from 3% to 6%, while the permeability ranges from 0.001 to 1.27 mD, with an average of 0.106 mD. Combined with the isothermal adsorption experiments, the proportion of mesopores is the largest in the Longmaxi shale, followed by macropores and micropores. Moreover, the pore diameters of mesopores are concentrated between 3 and 10 nm, while those of micropores are concentrated between 0.4 and 0.9 nm. The pore volume of shale is most developed when the content of brittle felsic minerals is 50% ~ 75% and the content of clay minerals is 25% ~ 50%, and the TOC content is positively correlated with the pore volume and specific surface area. There are significant differences in the pore development characteristics of different lithofacies. The shale reservoir space analysis indicates that micropores are controlled by TOC content and clay minerals, while the macropores are controlled by depositional intergranular pores, TOC content, and felsic content, as well as diagenetic pyrite mould pores, microfractures pores, and intercrystalline pores. On the other hand, mesopores are related to a mix of depositional and diagenetic factors with dominant contribution of intergranular pores, intercrystalline pores, organic pores, and intergranular shrinkage fractures pores. It is found that the pore development of massive organic‐rich siliceous shale lithofacies has the best reservoir quality, including well‐connected intergranular pores, intercrystalline pores, organic pores, and shrinkage fractures. Therefore, the massive organic‐rich siliceous shale lithofacies is the dominant fine‐grained reservoir lithofacies in the studied area. Based on understating the pore characteristics of different lithofacies, this study can provide a scientific basis for the prediction of favourable sweet spots of shale gas reservoir in the Longmaxi Formation, western Hunan‐Hubei Region.