Fixed-bed Experiments Research Articles

The effects of interaction between vermiculite and manganese dioxide on the environmental geochemical process of thallium

The interaction among various soil minerals can significantly impact on the environmental geochemical process of contaminants. Therefore, this study investigated the effects of interaction between vermiculite (VER) and manganese dioxide (MnO2) on the migration and transformation of Tl(I). The VER exhibited typical layered structure and MnO2 possessed a flower-like structure with serious reunion phenomenon, while the production of interaction between vermiculite and manganese dioxide, labeled VER-MnO2, illustrated as fish scales evenly spread over a large sheet, suggesting that MnO2 could triumphantly be anchored on the VER and the aggregation of MnO2 was prevented. Compared with the pure MnO2, VER acted as template substrate contributed the higher specific surface area (298.18 m2·g−1) and the oxidation degree of Mn. VER-MnO2 showed the highest fixation capacity (144.29 mg·g−1) than other two materials in the order VER-MnO2 > MnO2 > VER, and there was no risk derived from Mn dissolution. The influence mechanism of VER-MnO2 on Tl(I) migration and transformation lied in immobilization, ion exchange and oxidization. Fixed-bed column immobilization experiments showed that VER-MnO2 could purify drinking water contaminated by Tl (20 μg·L−1) and the effective breakthrough volumes were 900 bed volumes until reaching the maximum limits allowed in drinking water (0.1 μg·L−1). VER-MnO2 excellently catches Tl to prevent groundwater pollution. This study provides a theoretical guidance for environmental fate and restoration of soil heavy metal pollution.

The behavior of heteroatom compounds during the pyrolysis of waste computer casing plastic under various heating conditions

Single step and two-step pyrolysis of waste computer casing plastic were conducted to optimize both the product distribution and characteristics of liquid products. The single step pyrolysis was performed under various final temperatures ranging from 350 to 600 °C. The two-step pyrolysis was undertaken by initially increasing the temperatures to 350–380 °C and holding for 15 min, followed by a further increase to a peak temperature of 500 °C. The pyrolysis kinetic studies showed the activation energy of the two stages against conversion and revealed the synergistic reactions between BFR additives and plastic matrix. In the single step pyrolysis, fixed bed experiments showed that the final pyrolysis temperature had a significant influence on the product yield. The highest yield of 45.3 wt% oil was produced at 500 °C. The oil products mainly consisted of aromatic compounds, phenolic compounds, nitrogen-containing compounds, and approximately 11.3–15.9 wt% of toxic bromine. For the two-step pyrolysis, the impurities of O-, N- and Br-containing compounds were mainly enriched in the pyrolytic oils from the first step. Comparatively, more than 57% of single aromatic compounds was obtained in the pyrolytic oils from the second step, with less than 2.0 wt% of bromine. Meanwhile, the depolymerization of the plastic for the formation of styrene was promoted at the second step. The results suggested that in the two stage pyrolysis, bromine can be transferred into the liquid phase in the first stage, thus producing bromine containing compounds deficient oil in the second stage.

Effect of A-/B-site Doping on Oxygen Non-Stoichiometry, Structure characteristics, and O2 Releasing Behavior of La1−xCaxCo1−yFeyO3−δ Perovskites

Oxy-fuel combustion is one of the proposed technologies with the potential to achieve zero CO2 emission. La1−xCaxCo1−yFeyO3−δ (LCCF) perovskites are promising materials with high selectively for oxygen. In this study, the oxygen non-stoichiometry of perovskites LCCF was investigated by means of iodometric titration. LCCF was prepared using the liquid citrate method, and the phase structures were identified by X-ray diffraction. Fixed-bed experiments were performed to study the oxygen desorption performance of LCCF. The oxygen deficiency of LCCF increased with increasing Ca molar content of A site, but the value of δ of LCCF with increasing Fe molar content in B site is nearly constant. Experimental observation demonstrated that the O2 release amount of LCCF does not depend on oxygen non-stoichiometry δ generated from A-site doping. At the same time, doping Fe in B site has an obvious impact on the oxygen desorption amount.

Reactivity improvement of ilmenite by calcium nitrate melt infiltration for Chemical Looping Combustion of biomass

Chemical Looping Combustion is a novel process that generates sequestration-ready CO2 from the combustion of woody biomass without requiring a gas separation step and without diluting the CO2 with N2 from air. This is achieved by oxidizing the fuel with lattice oxygen of a metal oxide oxygen carrier. When using cheap and abundant ilmenite ore (FeTiO3) as the oxygen carrier, the rather low reactivity towards volatiles released from the biomass upon devolatilization, as well as detrimental structural changes due to a segregation of Fe and Ti in the material, are of concern. These issues can be addressed by modifying ilmenite with Ca via melt infiltration. In this work, we demonstrate that this modification results in a good distribution of Ca throughout the ilmenite particles that a) prevents detrimental Fe/Ti segregation, b) improves the mechanical stability of the particle compared to materials prepared by solution impregnation and c) improves the reactivity of this material towards hydrogen and wet methane. Moreover, fixed bed experiments showed that the Ca modification not only resulted in increased methane conversion, but also in an increased degree of oxidation of gaseous intermediates CO and H2. We thus conclude that the performance of ilmenite in Chemical Looping processes can be significantly enhanced by Ca modification of ilmenite either prior to use or in-situ during operation of this bed material with Ca-rich fuels such as woody biomass.

Concurrent adsorption and micro-electrolysis of Cr(VI) by nanoscale zerovalent iron/biochar/Ca-alginate composite

This study introduced a new approach for simultaneously enhancing Cr(VI) removal performance and mitigating release of dissolved Fe during nanoscale zero-valent iron (nZVI)-mediated reactions. After entrapping nZVI-impregnated biochar (BC) in the matrix of calcium-alginate (CA) bead, the physicochemical characterization of nZVI/BC/CA composites revealed that nZVI/BC particles were embedded inside CA having a spherical shape and several cracks on its outer layer. The multi-functionality of nZVI/BC/CA composites consisting of reductant (nZVI), porous adsorbent (BC), and external screening layer (CA) enhanced the removal of Cr(VI) with the maximum adsorption capacity of 86.4 mg/g (based on the Langmuir isotherm) and little release of dissolved Fe. With the XPS analysis and fitting results of kinetics (pseudo second order) and isotherms (Redlich-Peterson model), plausible removal mechanisms of Cr(VI) were simultaneous adsorption and micro-electrolysis reactions by nZVI/BC/CA composites. The practical applicability of nZVI/BC/CA composites was further demonstrated through the fixed-bed column experiments. These results provide new insights into the design of high-performance engineered biochar for wastewater treatment.

Immobilization of layered double hydroxide in poly(vinylidene fluoride)/poly(vinyl alcohol) polymer matrices to synthesize bead-type adsorbents for phosphate removal from natural water

Layered double hydroxide (LDH) has been widely used as an adsorbent to remove contaminants from aqueous solutions. However, LDH in powder form might not be suitable in water and wastewater treatment systems due to low hydraulic conductivity and sludge production. Therefore, it is necessary to synthesize bead-type adsorbents for application in treatment systems. In this study, LDH beads were prepared through immobilization of powdered MgFe LDH in polymer matrices, composed of poly(vinylidene fluoride) and poly(vinyl alcohol). The LDH beads had an average size of 2.4 ± 0.6 mm with a Brunauer-Emmett-Teller (BET) specific surface area of 30.41 m2/g and total pore volume of 0.12 cm3/g. Batch experiments were conducted on the use of the LDH beads for phosphate sorption in stream water (pH = 6.9, ionic strength = 613 μS/cm) collected from the Seoho stream located in Suwon, Korea. Fourier-transform infrared (FTIR) spectrometer and X-ray photoelectron spectroscopy (XPS) were used to analyze the chemical characteristics of the LDH beads before and after phosphate sorption. Phosphate sorption to the LDH beads remained relatively constant at initial pH values of 5–9. The LDH beads could be used repeatedly for phosphate sorption through desorption with a NaOH solution. The equilibrium time for the phosphate sorption was 3 h, whereas the maximum sorption capacity was 2.050 mgP/g. In addition, the phosphate sorption increased with a rise in temperature from 15 to 45 °C. Under dynamic flow conditions (flow rate = 4.9 and 9.8 mL/min; bed depth = 10, 20, and 30 cm; inner diameter of column = 2.5 cm), fixed-bed column experiments were performed to test the applicability of the LDH beads in the phosphate removal from the stream water. The phosphate sorption capacity of the column was quantified to be 1.175 mgP/g at given experimental conditions (bed depth = 30 cm; flow rate = 4.9 mL/min). The performance of fixed-bed columns was quantified by analyzing phosphate breakthrough curves with fixed-bed kinetic sorption models (Bohart-Adams and modified dose-response models). This study demonstrated that the LDH beads could be successfully applied as adsorbents for phosphate removal from natural water.

Conversion of waste polystyrene foam into sulfonated hyper-crosslinked polymeric adsorbents for cadmium removal in a fixed-bed column

In this paper, the sulfonated hyper-crosslinked polystyrene (SHCP) adsorbents derived from the waste expanded polystyrene foam (WEPS) were prepared by the simple one-step Friedel–Crafts reaction and the subsequent sulfonation. The prepared SHCP adsorbents were used for the first time in the fixed-bed dynamic adsorption experiments for the removal of cadmium (Cd) ions. The maximum adsorption capacity of SHCP for Cd ion reached 0.7mmol/g at the pH of 7 at the temperature of 25°C. The influencing factors of the actual industrial wastewater including initial Cd ion concentration, height-to-diameter (H/d) ratio, ionic strength and co-existing ions on Cd ion adsorption breakthrough curve were examined in a fixed-bed column with the SHCP adsorbents. Furthermore, Thomas model was employed to fit the adsorption breakthrough curve and the simulated adsorption capacity ranged from 68.90 to 80.46mg/g, with the correlation coefficient higher than 0.97. It was found that the decrease of the ionic strength and the Cd ion initial concentration, as well as the increase of the H/d ratio would increase the adsorption capacity and the breakthrough point in the Cd ion column adsorption. In addition, the SHCP showed good Cd ion selectivity over Na ions in the column adsorption.

Pre-evaluation of strong base anion exchange, Amberlite IRA 958-Cl resin for nitrate removal

Abstract High concentration of nitrate in water either in surface or groundwater is an effect from agricultural activities, domestic use and industrial activities. Hence, removing enormous nitrate from water is necessary because it can be hazardous to the human health and aquatic life. The ion exchange resin is the most widely used technology in removing nitrate from water source. In this study, commercial strong anion exchange resin, Amberlite IRA 958-Cl was used to study the efficiency of nitrate removal from aqueous solution in a fixed-bed column experiment. The influence of resin dosage (0.05 to 0.20 g), contact time (1 to 4 hours) and initial nitrate concentration (20, 50, 100 and 200 mg/L) were examined. More than 87% of nitrate removal achieved at 0.1 g (2 g/L) of resin dosage, 3 hours of contact time and 20 mg/L of initial nitrate concentration. This promising result make that Amberlite IRA 958-Cl can become an attractive candidate as adsorbent for nitrate removal.

Sustainable utilization of a recovered struvite/diatomite compound for lead immobilization in contaminated soil: potential, mechanism, efficiency, and risk assessment.

A waste-struvite/diatomite compound (MAP@Dia) recovered from nutrient-rich wastewater treated by MgO-modified diatomite (MgO@Dia) was provided to immobilize lead in aqueous solution and contaminated soil. The mechanism and effectiveness of lead immobilization was investigated, and the pHstat leaching test and fixed-bed column experiments were carried out to assess the risk of MAP@Dia reuse for lead immobilization. The results showed that MAP@Dia were effective in immobilizing lead in aqueous solution with adsorption capacity of 832.47-946.50mg/g. The main mechanism of Pb immobilization by MAP@Dia could be contributed by surface complexation and dissolution of struvite followed by precipitation of hydroxypyromorphite Pb10(PO4)6(OH)2. Lead(II) concentration reduced from 269.61 to 78.26mg/kg, and residual lead(II) increased to 53.14% in contaminated soil when the MAP@Dia application rate was 5%. The increased neutralization capacity (ANC) and lower lead extraction yields in pHstat leaching test in amended soil suggested 5 times of buffering capacity against potential acidic stresses and delayed triggering of "chemical time bombs." The results of column studies demonstrated that amendment with MAP@Dia could reduce the risk of lead and phosphorus (P) leaching. This study revealed that MAP@Dia could provide an effective solution for both P recycling and lead immobilization in contaminated soil.

Exceptional adsorption of arsenic by zirconium metal-organic frameworks: Engineering exploration and mechanism insight

Highly stable zirconium metal-organic frameworks (UiO-66 and UiO-66(NH2)) had been synthesized and investigated to remove arsenic (As) from contaminated water. The As(III, V) removal performance was studied by batch experiments and adsorption kinetics. At the pH of 9.2 ± 0.1, UiO-66 had exceptional removal capacities of 205.0 and 68.21 mg/g for As(III) and As(V), respectively. The As removal processes were exothermic and verified as chemisorption reactions according to the calculation of Gibbs free energy and Dubinin-Radushkevich (D-R) isotherm model. Fixed-bed reactor removal experiments indicated that the number of effective treatment volumes reached 2270 and 1775 BVs for As(III) and As(V), respectively, until the most stringent As regulation level of 10 μg/L (initial As concentration at 100 μg/L) was reached. FTIR and XPS study indicated that ZrO bonds of zirconium metal-organic frameworks played a vital role in As adsorption. XANES revealed the As adsorption on UiO-66 without the change of oxidation state. More intriguingly, EXAFS spectra demonstrated the main formation of bidentate mononuclear complexes for As(V), and bidentate binuclear complexes for As(III) on the hexanuclear Zr cluster of UiO-66. The advantages of nontoxicity, high stability, high As adsorption capacity, low-cost and easy availability confirm the highly promising application of zirconium metal-organic frameworks in As-contaminated wastewater remediation.

Simultaneous removal of As(V)/Cr(VI) and acid orange 7 (AO7) by nanosized ordered magnetic mesoporous Fe-Ce bimetal oxides: Behavior and mechanism

In this study, nanosized ordered magnetic mesoporous Fe-Ce bimetal oxides (Nanosized-MMIC) with highly well-ordered inner-connected mesostructure were successfully synthesized through the KIT-6 template method. This Nanosized-MMIC displayed excellent adsorption capacities for As(V), Cr(VI) and AO7, and the corresponding calculated maximum adsorption capacities of material were 111.17, 125.28 and 156.52 mg/g, respectively. As(V) and Cr(VI) removal by Nanosized-MMIC were slightly dependent on the ionic strength but highly solution pH-dependent, the coexistent silicate and phosphate ions competed remarkably with both As(V) and Cr(VI) for the adsorption active site. Mechanisms indicated As(V) and Cr(VI) formed inner-sphere complexes on Nanosized-MMIC interface via the electrostatic interaction and surface complexation, while the total organic carbon (TOC) change demonstrated that AO7 could be removed completely and no organic intermediates formed through the adsorption process. In addition, Nanosized-MMIC also possessed superior adsorption performance in As(V)/Cr(VI)-AO7 binary systems, and the reusable and regeneration properties indicated that the obtained nanomaterials could maintain at a comparatively high level after several recycling. Finally, fixed-bed experiments suggested the Nanosized-MMIC was expected to have a promising excellent nano-adsorbent with high application potential for co-existed toxic heavy metals and organic dyes removal in practical wastewater treatment.

Facile synthesis and low concentration tylosin adsorption performance of chitosan/cellulose nanocomposite microspheres

Antibiotic pollution in tap water, surface water, and effluent needs to be controlled in China. Adsorption is an economical and eco-friendly way to solve the antibiotic contamination problem, such as tylosin. In this study, the chitosan/cellulose nanocomposite adsorbents entrapped with activated carbon are prepared by a sol-gel phase inversion method. Structures and properties of the adsorbents are characterized by SEM, EDXS, BET, XRD, FTIR XPS and Zeta potentials. The adsorption behavior of CCM-AC on tylosin is determined by batch and fixed-bed adsorption experiments, while their adsorption mechanism is also studied. The maximum adsorption capacity is 59.26 mg g−1, while the adsorption behavior is in accordance with the Langmuir equation and pseudo-second-order kinetics. These results confirm that the tylosin adsorption process is affected by chemical and physical interactions, and the adsorbent can be captured by tylosin with H-bond, electrostatic and π-π electron-donor-acceptor interaction. Adsorption experiments are significantly affected by pH.

Potential of Araucaria angustifolia bark as adsorbent to remove Gentian Violet dye from aqueous effluents.

Araucaria angustifolia bark (AA-bark), a waste generated in wood processing, was evaluated as a potential adsorbent to remove Gentian Violet (GV) dye from aqueous solutions. The AA-bark presented an amorphous structure with irregular surface and was composed mainly of lignin and holocellulose. These characteristics indicated that the adsorbent contains available sites to accommodate the dye molecules. The GV adsorption on AA-bark was favored at pH 8.0 with adsorbent dosage of 0.80 g L-1. Pseudo-nth order model was adequate to represent the adsorption kinetics of GV on AA-bark. A fast adsorption rate was verified, with the equilibrium being attained within 30 min. Equilibrium data were well represented by the Langmuir model. The maximum adsorption capacity was 305.3 mg g-1. Adsorption was spontaneous, favorable and endothermic. AA-bark was able to treat a simulated dye house effluent, reaching color removal values of 80%. An excellent performance was found in fixed bed experiments, where the length of the mass transfer zone was only 5.38 cm and the breakthrough time was 138.5 h. AA-bark can be regenerated two times using HNO3 0.5 mol L-1. AA-bark can be used as a low-cost material to treat colored effluents in batch and fixed bed adsorption systems.

Novel glucosamine-based carbon adsorbents with high capacity and its enhanced mechanism of preferential adsorption of C2H6 over C2H4

In this work, we synthesized a series of glucosamine-based carbon adsorbents with rich microporosity for effective C2H6/C2H4 adsorptive separation. Glucosamine was chosen as precursor to synthesize new microporous glucosamine-based carbon adsorbents (MGAs) and the resultant adsorbents were then characterized. Results showed that the BET surface area and pore volume of the MGAs reached as high as 3189 m2/g and 1.92 cm3/g, respectively. The FTIR and XPS results showed the presence of abundant N/O groups on carbon surface. Ethane and ethylene adsorption isotherms of the materials were then measured. The effects of N/O functionalities and micropore sizes on C2H6 and C2H4 adsorption were also elaborated by using molecular simulation. Interestingly, the materials presented preferential adsorption of ethane over ethylene with its ethane adsorption capacity reaching 7.6 mmol/g under 1 bar and 25 °C. Its adsorption selectivity for ethane/ethylene (1:1) was improved and higher than many MOFs, being in the range of 2.2–6.8 at <1 bar and 25 °C. Molecular simulation revealed the synergistic effects of the micropore aperture size and the surface N/O functionalities of MGAs on its adsorption property, especially adsorption selectivity toward C2H6/C2H4. An increase in amounts of surface N/O functionalities in the micropores with the aperture size in 6–10 Å of MGAs played an important role in the enhanced interaction of C2H6 with the surfaces, thus resulting in further improvement of ethane/ethylene selectivity. Fixed-bed breakthrough experiments demonstrated the complete separation of C2H6/C2H4 mixture at room temperature by using the glucosamine-based carbons. These excellent adsorption properties make the glucosamine-based carbon materials a type of promising C2H6-selective adsorbents for the effective separation of C2H6/C2H4.

Highly porous zirconium-crosslinked graphene oxide/alginate aerogel beads for enhanced phosphate removal

The decontamination of excessive phosphate by Zr-based nanomaterials has attracted great attention. However, the insufficient phosphate sorption capacities and separation difficulties significantly restrict the potential applications. Herein, the newly designed zirconium-crosslinked graphene oxide/alginate (Zr-GO/Alg) aerogel beads were synthesized through a facile in situ crosslinking method, and their phosphate uptake performance were examined in the aqueous environment under different conditions. Characterization results showed that the incorporation of GO endowed the composite beads with a more porous and reinforced structure. The maximum sorption capacity was 189.06 mg P/g and the isotherm data were well fitted to the Freundlich model. Fixed-bed column experiments showed a large throughput of ∼1050 BV, with phosphate concentration of effluents lower than 0.5 mg/L. Apart from the remarkable phosphate uptake performance, the fast adsorption rate at initial stage as well as easy separation feature of Zr-GO/Alg aerogel beads rendered them to become promising and environmental-friendly adsorbentfor phosphate uptake from polluted water.

Competitive adsorption of heavy metal ions (Pb2+, Cu2+, and Ni2+) onto date seed biochar: batch and fixed bed experiments

ABSTRACTIn a multicomponent systems, the adsorption of Pb2+, Cu2+, and Ni2+ by date seed biochar exhibited competitive behavior. Compared to single component systems, the adsorption capacities of each ion were reduced by 48–75% in both batch and column experiments. Surface complexation with carboxyl and hydroxyl functional groups played a major role in the removal mechanism. Ion exchange mechanism accounted for 37–40% of the total adsorption compared to 57–72% in single component systems. Modified Langmuir isotherm best described the systems. Adsorption capacities and selectivity follow the order: Pb2+> Cu2+> Ni2+. Multi-stage sequences system is recommended to avoid premature exhaustion of biochar.

Lactic acid recovery from a model of Thermotoga neapolitana fermentation broth using ion exchange resins in batch and fixed-bed reactors

ABSTRACTThis study focused on the integration of lactic acid adsorption and desorption onto commercially available resins in batch reactors with consequent scale-up in fixed-bed reactors. Amberlite® IRA-900, IRA-400, IRA-96 and IRA-67 were used as adsorbents for lactic acid recovery from solutions that mimic the fermentation broth of Thermotoga neapolitana. The best resins were further tested in adsorption–desorption batch experiments, over 13 cycles, with IRA-67 showing an average removal efficiency of 97%. IRA-67 was tested in fixed-bed reactor experiments and an average desorption efficiency of 68% was achieved using three bed volumes of 0.5 M NaOH as the desorbing agent.

Enhanced bisphenol A removal from stormwater in biochar-amended biofilters: Combined with batch sorption and fixed-bed column studies

A high-efficient, low-cost, and practical biochar implementation method is desired to extend biochar's powerful adsorption performance for environmental remediation. This study presents novel results with advanced biochar application by integrating biochar with biofilter for the removal of bisphenol A (BPA) from stormwater. Biochars derived from wood dust (BC0) at different pyrolytic temperatures (300, 500, and 700 °C, referred as, BC300, BC500, and BC700, respectively) were characterized and investigated for their adsorption of BPA under different pH levels and humic acid (HA) concentrations by batch sorption and fixed-bed column experiments. Microcosm biofilters vegetated with phragmites australis and amended with different biochars were constructed and used for BPA removal under different hydraulic loading rates (HLRs). Compared with other biochars, BC700 showed a high adsorption rate and capacity due to high specific surface area and pore volume. As a consequence, fixed-bed columns amended with BC700 can remove BPA more efficiently than columns with BC0, BC300, and BC500 from synthetic stormwater, though the treatment performance was affected relatively by pH change and HA concentration. A high correlation (r2 = 0.899) between the breakthrough time and the product of adsorption rate (k2) and capacity (Qmax) was found, which suggests that batch sorption experiments could be an efficient tool for prediction of breakthrough time. The BPA removal efficiency of microcosm biofilters amended with BC0, BC300, BC500 and BC700 for real stormwater containing 200 μg/L BPA at HLR of 40 cm/h averaged 4.1, 10.8, 80.3, and 98.4%, which were about 6, 15, 115, and 141 times, respectively, compared to bilfitlers without biochar amendment. Moreover, biochar amendment not only enhanced the BPA removal but also promoted phragmites australis growth, elevated nutrients and increased the E. coli removal efficiency. Hence, biochar-amended biofilters could be a promising approach for enhancing the elimination of endocrine-disrupting chemicals such as BPA from aqueous environments.

Biporous Metal-Organic Framework with Tunable CO2/CH4 Separation Performance Facilitated by Intrinsic Flexibility.

In this work, we report the synthesis of SION-8, a novel metal–organic framework (MOF) based on Ca(II) and a tetracarboxylate ligand TBAPy4– endowed with two chemically distinct types of pores characterized by their hydrophobic and hydrophilic properties. By altering the activation conditions, we gained access to two bulk materials: the fully activated SION-8F and the partially activated SION-8P with exclusively the hydrophobic pores activated. SION-8P shows high affinity for both CO2 (Qst = 28.4 kJ/mol) and CH4 (Qst = 21.4 kJ/mol), while upon full activation, the difference in affinity for CO2 (Qst = 23.4 kJ/mol) and CH4 (Qst = 16.0 kJ/mol) is more pronounced. The intrinsic flexibility of both materials results in complex adsorption behavior and greater adsorption of gas molecules than if the materials were rigid. Their CO2/CH4 separation performance was tested in fixed-bed breakthrough experiments using binary gas mixtures of different compositions and rationalized in terms of molecular interactions. SION-8F showed a 40–160% increase (depending on the temperature and the gas mixture composition probed) of the CO2/CH4 dynamic breakthrough selectivity compared to SION-8P, demonstrating the possibility to rationally tune the separation performance of a single MOF by manipulating the stepwise activation made possible by the MOF’s biporous nature.

Removal and recovery of phosphate from water by Mg-laden biochar: Batch and column studies

The work investigated the potential application of Mg-laden biochar prepared from Mg-enriched bamboo to remove and recover phosphate from water. The Mg-laden biochar samples were synthesized at 400 °C, 500 °C and 600 °C. With the increasing synthesized temperature, the production rate of adsorbent decreased but the Mg content and specific surface area increased. Factors on phosphate adsorption including kinetic, isotherm, pH, dosage were examined through batch experiments. The maximum phosphate adsorption amount was 344, 357 and 370 mg/g for biochar-Mg-400, biochar-Mg-500 and biochar-Mg-600, respectively. The effect of phosphate adsorption on Mg-laden biochar samples was also investigated by fixed-bed column experiments, and the maximum adsorption amount calculated by Thomas model was 60.7, 61.2 and 62.2 mg/g, respectively. The adsorbed phosphate could be successfully desorbed by 3 M NaOH solution and the regenerated Mg-laden biochar samples could be reused at least 5 times for phosphate adsorption. The bioavailability of postsorption biochar was proved very well through the Mehlich 3 method. Phosphate adsorption characteristic and FTIR analysis indicated that the adsorption was mainly controlled by two mechanisms: ligand exchange and electrostatic attraction.