Composite Adsorbent Research Articles

Removal of cadmium in aqueous solutions using a ball milling-assisted one-pot pyrolyzed iron-biochar composite derived from cotton husk.

A novel iron-biochar composite adsorbent was produced via ball milling-assisted one-pot pyrolyzed BM-nZVI-BC 800. Characterization proved that nano zero valent iron was successfully embedded in the newly produced biochar, and the nZVI payload was higher than that of traditional one-pot pyrolyzed methods. BM-nZVI-BC 800 provided a high adsorption performance of cadmium reaching 96.40mg·g-1 during batch testing. Alkaline conditions were beneficial for cadmium removal of BM-nZVI-BC 800. The pseudo-second-order kinetic model and Langmuir isotherm fitted better, demonstrating that the Cd adsorption on the BM-nZVI-BC 800 was a chemical and surface process. The intraparticle diffusion controlled the adsorption of BM-nZVI-BC 800. The physisorption dominated by high specific surface area and mesoporous structure was the primary mechanism in the removal of cadmium, though electrostatic attraction and complexation also played a secondary role in cadmium adsorption. Compared to adsorbents prepared by more traditional methods, the efficiencies of the ball milling-assisted one-pot pyrolyzed method appears superior.

Multilayer Graphene Oxide Supported ZIF-8 for Efficient Removal of Copper Ions

HighlightsA multilayer graphene based adsorbent was prepared by a simple method;Adsorbents have high adsorption capacity and a high specific surface area;The multilayer structure of graphene layer provides a framework for ZIF, adding more adsorption sites.To address the performance deterioration of ZIF-8 for the adsorption of copper ions caused by powder volume pressure and particle aggregation, we employed multilayer graphene oxide (MGO) as a support to prepare composite adsorbents (MGO@ZIF-8) by using the in situ growth of ZIF-8 on MGO. Due to a good interfacial compatibility and affinity between ZIF-8 and graphene nanosheets, the MGO@ZIF-8 was successfully prepared. The optimal Cu2+ adsorption conditions of MGO@ZIF-8 were obtained through single factor experiments and orthogonal experiments. Surprisingly, the Cu2+ adsorption capacity was significantly improved by the integration of MGO and ZIF-8, and the maximum Cu2+ adsorption capacity of MGO@ZIF-8 reached 431.63 mg/g under the optimal adsorption conditions. Furthermore, the kinetic fitting and isotherm curve fitting confirmed that the adsorption law of Cu2+ by MGO@ZIF-8 was the pseudo-second-order kinetic model and the Langmuir isotherm model, which indicated that the process of Cu2+ adsorption was monolayer chemisorption. This work provides a new approach for designing and constructing ZIF-8 composites, and also offers an efficient means for the removal of heavy metals.

Investigation on water vapor adsorption performance of carbon based composite adsorption material ACF-silica sol-LiCl

The composite adsorption material ACF-silica sol-LiCl (ASL) is prepared by impregnating activated carbon fiber (ACF) with silica sol and LiCl to improve the water vapor adsorption performance. The silica sol provides support to the soft ACF and solidifies it. The silica sol also increases the adhesion area in the ACF for the LiCl. The LiCl can effectively improve the water vapor adsorption performance of the ACF. The adsorption performance of the ASL is optimum when the LiCl impregnation concentration is 430 mg/L. Scanning electron microscope images show that the silica sol and LiCl fill the fibers pores and spaces between the fibers in the ACF after impregnation. And adsorption kinetics of the ASL is characterized using a linear driving force (LDF) model and experiments. Results show that ASL has a high dynamic water absorption rate and adsorption rate coefficient (k). The k of the ASL reaches 1.58 × 10−4−2.05 × 10−4, which is 0.27 × 10−4−0.59 × 10−4 higher than that of the ACF. Meanwhile, the results of water vapor isothermal adsorption tests show that the impregnation of silica sol and LiCl increases the hydrophilicity of the ACF, and thus greatly enhances its water vapor adsorption capacity. The adsorption capacity of the ACF is almost 0 at P/P0 < 0.2 and reaches a maximum of 0.5479 g/g at P/P0 = 0.65. The adsorption capacity of the ASL steadily increases with the relative pressure. When the relative pressure is close to 1, the adsorption capacity of the ASL reaches 2.2876 g/g, which is 2.67 times the maximum for the ACF.

Preparation and Phosphorus Removal Performance of Zr–La–Fe Ternary Composite Adsorbent Embedded with Sodium Alginate

Using single metal salts of zirconium, lanthanum, and iron as raw materials and sodium alginate as a cross-linking agent, a new composite adsorbent was prepared via the co-precipitation method and embedding immobilization technology, and its phosphorus adsorption performance in wastewater was evaluated. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used for characterization, and a 0.5 mol·L−1 sodium hydroxide solution was used to regenerate the adsorbent. The experimental results demonstrated that the adsorption rate reached 99.88% when the wastewater volume was 50 mL, the initial concentration of phosphorus-containing wastewater was 5 mg·L−1, the pH was 5, the dosage of composite adsorbent was 0.2 g, and the adsorption time was 200 min. The prepared adsorbent could reduce the initial phosphorus concentration of 5 mg·L−1 to 0.006 mg·L−1 in simulated wastewater, and from 4.17 mg·L−1 in urban sewage to undetected (&lt;0.01 mg·L−1), thus meeting the discharge requirements of the grade A standard of the Urban Sewage Treatment Plant Pollutant Discharge Standard (GB18918-2002). The adsorption process conformed to the Freundlich adsorption isothermal equation and quasi-second-order kinetic equation, and the adsorption reaction was exothermic and spontaneous. More importantly, after three lye regeneration tests, the removal rate of phosphorus in water remained above 68%, that is, the composite adsorbent could be reproducibly fabricated and recycled. The characterization results showed that the surface of the composite adsorbent was rough, with a complex pore structure. After phosphorus removal, the surface morphology of the composite adsorbent showed a similar honeycomb structure, with a P-H, P-O stretching vibration peak and a characteristic P2p peak. At the same time, the proportion of hydroxyl groups (M-OH) on the metal surface decreased after adsorption. Our findings thus demonstrate that the mechanism of phosphorus removal is mainly based on the coordination exchange reaction between phosphate and metal active sites and surface hydroxyl groups, resulting in the formation of granular phosphate deposits.

A study on activated carbon and carbon nanotube based consolidated composite adsorbents for cooling applications

MWCNT based composites enhance the thermal conductivity of the parent activated carbon, and they exhibit a higher volumetric cooling effect than other promising composites. • Synthesis of Activated carbon (AC)-multiwalled carbon nanotube (MWCNT) composites. • AC-MWCNT composites possess higher packing density than parent AC. • AC-MWCNT composites reveal improved thermal conductivity over parent AC. • MWCNT contributes to the CO 2 adsorption capacity of composite adsorbents. • AC-MWCNT composites exhibit improved SCE and COP over other AC-based composites. Activated carbon (AC)/CO 2 pair is very promising for developing an efficient adsorption cooling system (ACS). However, the low packing density and poor heat transfer properties of activated carbon-based ACS prevent their widespread adoption. Addressing these issues, this study focuses on the synthesis and characterization of AC-based consolidated composites comprising Maxsorb III (one type of AC) as adsorbent, multi-walled carbon nanotube (MWCNT) as thermal conductivity enhancer (TCE), and polyvinyl alcohol (PVA) as the binder. The influence of MWCNT on the porous properties, thermal diffusivity, thermal conductivity, and CO 2 adsorption capacity of composite adsorbents has been experimentally investigated. Besides, performance parameters, including the specific cooling effect (SCE) and coefficient of performance (COP), have been theoretically determined under different working conditions. Porous properties results show that developed composites are microporous like AC and exhibit high surface area and pore volume compared to other AC-based composite adsorbents developed so far. The incorporation of MWCNT into AC results in enhancing packing density, thermal diffusivity, and conductivity. One of the developed composites exhibits 2.47 and 3.5 times higher packing density and thermal conductivity than that of parent AC. Besides, the CO 2 adsorption study concludes regarding the contribution of MWCNT in the CO 2 adsorption capacity of composite adsorbents, which in turn results in the improved CO 2 uptake, SCE, and COP over other AC composites found in the literature. This study's findings will greatly stimulate the development of an efficient and compact adsorption cooling system.

Removal of Arsenic from Wastewater by Using Nano Fe3O4/Zinc Organic Frameworks.

Efficient removal of arsenic in wastewater is of fundamental importance due to the increasingly severe arsenic pollution. In this study, a new composite adsorbent (Fe3O4@ZIF-8) for As(V) removal from wastewater was synthesized by encapsulating magnetic Fe3O4 nanoparticles into metal organic frameworks. In order to evaluate the feasibility of Fe3O4@ZIF-8 as an adsorbent for As(V) removal, the adsorption properties of Fe3O4@ZIF-8 were systematically explored by studying the effects of dosage, pH, adsorption isotherm, kinetics, and thermodynamics. Additionally, the characterization of Fe3O4@ZIF-8 before and after adsorption was analyzed thoroughly using various tests including SEM-EDS, XPS, BET, XRD, TG, FTIR, and the properties and arsenic removal mechanism of the Fe3O4@ZIF-8 were further studied. The results showed that the Fe3O4@ZIF-8 has a specific surface area of 316 m2/g and has excellent adsorption performance. At 25 °C, the initial concentration of arsenic was 46.916 mg/L, and pH 3 was the optimum condition for the Fe3O4@ZIF-8 to adsorb arsenic. When the dosage of the Fe3O4@ZIF-8 was 0.60 g/L, the adsorption of arsenic by the Fe3O4@ZIF-8 can reach 76 mg/g, and the removal rate can reach 97.20%. The adsorption process of arsenic to the Fe3O4@ZIF-8 can be well described by the Langmuir isotherm model and the second-order kinetic equation. At pH 3 and temperature 298 K, the maximum adsorption capacity of arsenic by the Fe3O4@ZIF-8 was 116.114 mg/g. Through the analysis of thermodynamic parameters, it is proved that the adsorption process of arsenic by the Fe3O4@ZIF-8 is a spontaneous endothermic reaction. The Fe3O4@ZIF-8 has broad prospects for removing As(V) pollution in wastewater, because of its strong adsorption capacity, good water stability, and easy preparation.

Pollution Removal Performance of Chemically Functionalized Textile Waste Biochar Anchored Poly(vinylidene fluoride) Adsorbent

Preparation of adsorbent materials in powder and polymeric composite form was achieved by controlled carbonization of ZnCl2 pretreated textile waste at low temperatures. Structural and surface properties of carbonized textile waste samples (CTW) and polymeric composites were prepared by the addition of CTW to PVDF-DMF solution at 0, 5, 10, 15, 20, and 30 mass% ratios analyzed by FT-IR, XRD, SEM, and BET analysis. Adsorption performances of powder and composite adsorbents were investigated for MO dye removal from an aqueous solution. Zn-CTW obtained with carbonization of ZnCl2 treated textile waste at 350 °C presented 117.5 mg/g MO removal. Those were higher than CTW-350 and CTW-400. The presence of 1545 cm-1 band at the IR spectrum of Zn-CTW proved the formation of functional groups that increase dye adsorption performance with honeycomb-like pores on the surface. Zn-CTW reflected its properties onto the PVDF matrix. Improved porosity percentage, BET surface, and dye adsorption of Pz20 were recorded as 105.3, 15.22 m2/g, and 41 mg/g, respectively, compared with bare PVDF. Disposal of textile waste and preparation of functional activated carbon were achieved in a low-cost and easy way. Zn-CTW loaded PVDF composites are promising materials to use as a dye removal adsorbent from water or filtration membranes.

Combination of Corn Waste and Egg Shell as Zn Metal Adsorbent with Batch System

&lt;p&gt;This study aims to determine: the ability of corn cobs and eggshells as Zn metal adsorbents, functional groups of corn cobs and eggshells adsorbent, what isotherm patterns occur in the adsorbent corn cobs and eggshells in adsorbing Zn metal, the optimum ratio and optimum mass of the adsorbent composition of corn cobs and eggshells in Zn metal adsorption, the optimum contact time for adsorbent corn cobs and eggshell in adsorbing Zn metal, the optimum concentration of adsorbate to be adsorbed by corn cobs and eggshell adsorbents. This study used an experimental method in the laboratory. characterization includes functional groups using FTIR, and test the effectiveness of adsorbents using the AAS instrument. Kinetic analysis of adsorbent by adsorption isotherm with Langmuir isotherm, Freundlich isotherm, Temkin isotherm, and dubinin-radushkevivh isotherm. The results showed that: Corn cobs and eggshells can be used as zinc metal adsorbents; in the corn cobs adsorbent, there is a functional group -OH at wave number 3415,15 cm&lt;sup&gt;-1&lt;/sup&gt; and in the eggshell, there is a bent vibration of calcium carbonate at wave number 3400,65 cm&lt;sup&gt;-1&lt;/sup&gt;, the adsorption process of Zn metal by adsorbent corn cobs and egg shells follows the Langmuir isotherm pattern (chemical adsorption), the comparison of the optimum composition and mass of the adsorbent corn cobs and eggshells in Zn metal adsorption are 1:2 and 0,15 grams with Zn metal adsorbed by 80,4571%, the optimum contact time for the adsorbent corn cobs and eggshells in adsorbing Zn metal is 90 minutes with the percentage of absorbed Zn metal concentration is 75,5957%, and the optimum concentration of adsorbate for adsorbed by corn cob and eggshell adsorbents is 1 mg/L with adsorbed Zn percentage of 82,8377%.&lt;/p&gt;

Separable amino-functionalized biochar/alginate beads for efficient removal of Cr(VI) from original electroplating wastewater at room temperature

An alginate gel bead composite adsorbent with polyethyleneimine (PEI) as a surface modifier and Eichhornia crassipes (EC) biochar, known as EC-alg/PEI-3, was added internally to the adsorb Cr(VI) from an aqueous environment. The functionalized gel beads were characterized using SEM, XPS, FTIR, and other techniques. The maximum adsorption capacities of EC-alg/PEI-3 were 714.3 mg g−1 at 10 °C and 769.2 mg g−1 at 25 °C. In the treatment of highly concentrated electroplating wastewater, EC-alg/PEI-3 can be dosed at 1.4 g L−1 to reduce the concentration of Cr(VI) to below 0.05 ppm. EC-alg/PEI-3 maintained a competitive adsorption capacity after six cycles. This spherical adsorbent material is easy to prepare, has a very high adsorption capacity, is environmentally friendly, and can be easily recycled. The EC-alg/PEI-3 gel beads are promising for the treatment of industrial wastewater.

Preparation of a sulfonated coal@ZVI@chitosan-acrylic acid composite and study of its removal of groundwater Cr(VI).

In this research, a new composite adsorbent (SC@ZVI@CS-AA) was designed and synthesized, and its application for the removal of Cr(VI) in groundwater was investigated. The interaction between SC@ZVI@CS-AA and Cr(VI) conformed to a pseudo-second-order model, and the adsorption process was dominated by chemisorption. The effects of material ratios, pH, temperature, SC@ZVI@CS-AA dosage, and coexisting ions on the removal of Cr(VI) were investigated. The removal efficiency of Cr(VI) by SC@ZVI@CS-AA reached 95%, and the reaction was significantly inhibited when SO42- was present. Thermodynamically, the adsorption of Cr(VI) proceeded spontaneously above 35°C (ΔGθ < 0). According to scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometry, and synchronous thermal analysis, the removal mechanism of Cr(VI) by SC@ZVI@CS-AA was attributed to electrostatic attraction and reduction. In addition, SC@ZVI@CS-AA had good cyclic adsorption performance. Overall, the SC@ZVI@CS-AA composite showed great potential in the remediation of Cr(VI)-contaminated groundwater.

Removal of linear siloxanes and dimethyl sulfone from water using hierarchical zeolite porous carbon adsorbents

Low molecular weight linear siloxanes are problematic compounds known to occur in water bodies, especially in water reclaimed from closed volumes. Remediation was attempted using a hierarchical porous composite adsorbent containing a Faujasite zeolite imprinted in activated carbon, namely CFAU. Although CFAU was prepared using procedures reported elsewhere, it was modified also to include extra-framework Ag+ cations. The composites long-range, textural, and compositional characteristics were verified via XRD, nitrogen porosimetry, water contact angle, zeta potential, TGA, and ICP elemental analyses. Furthermore, the composites were tested for the adsorption of siloxanes (i.e., monomethylsilanetriol, dimethylsilanediol, and trimethylsilanol (TMS)) as well as dimethyl sulfone (DMSO2) from water (mg L−1 level) in single and multicomponent fashion at ambient temperature and neutral pH. DMSO2 is highly ubiquitous in reclaimed waters where these siloxanes occur. Ag+-CFAU was the superior adsorbent, with siloxane and DMSO2 loadings of up to 20 and 87 mg cm−3 (or 17 and 72 mg g−1), respectively. These are at least an order of magnitude larger than commercial alternatives like carbon and resins. FTIR data suggest that the adsorption interaction with siloxanes is of Van der Waals type, whereas interactions between Ag+-CFAU and DMSO2 plausibly involve complexation. Moreover, multicomponent adsorption tests showed that Ag+-CFAU excels probably because of the complexation with DMSO2 and a TMS-driven siloxane co-adsorption.

Polyethylene glycol functionalized reduced graphene oxide coupled with zinc oxide composite adsorbent for removal of phenolic wastewater

The development of agricultural activities and industrialization recently has various adverse impacts on living organisms. The ever-increasing problem of organic pollution has been an environmental concern to the community. Among these, phenolic pollutants like 2,4–dichlorophenol (2,4–DCP), phenol, 2–chlorophenol (2–CP), and bisphenol–A (BPA) are priority toxic pollutants that are continuously released into environment from many industries. In this work, a biocompatible zinc oxide incorporated polyethylene glycol functionalized reduced graphene oxide composite (RGO-PEG-ZnO) was synthesized and explored for the adsorptive removal of toxic phenolic pollutants from water. The optimized adsorption parameters were solution pH 7, adsorption time 60 min, temperature 25 °C, and dosage 0.25 g/L. The isotherms were well fitted by the Langmuir model for BPA and phenol, whereas for 2–CP, and 2,4–DCP, Freundlich was the best-fitted model, and the maximum uptake of BPA, phenol, 2–CP, and 2,4–DCP were 485.756, 511.248, 531.804, 570.641 mg/g, respectively. The kinetic data for all the phenolic pollutants follow the pseudo-second-order model. The thermodynamic analysis shows that Gibb's free energy (ΔGo) values for all the pollutants were negative, confirming that the process was spontaneous. The positive values of change in enthalpy (ΔHo) 28.261, 37.205, 46.182, and 61.682 kJ/mol for BPA, phenol, 2–CP, and 2,4–DCP, respectively, confirm that the above adsorption process was endothermic. The composite can be used for up to five cycles with a small reduction in the removal percentage. Adsorption performance of the synthesized composite for synthetic industrial effluents shows that up to 86.54% removal occurred in 45 min adsorption time. Based on the remarkably rapid adsorption and high adsorption capacity, RGO-PEG-ZnO composite can be considered an efficient adsorbent for treating phenolic pollutants from wastewater.

Resin-based iron-manganese binary oxide for phosphate selective removal.

Adsorption technology can effectively remove phosphorus from water and realize phosphorus recovery. Hence, it is used to curb the eutrophication of water and alleviate the crisis caused by the shortage of phosphorus resources. Resin has been attracting increasing interest as an ideal adsorption material; however, its practical application is greatly affected by environmental factors. To solve the competitive adsorption and pore blockage caused by humic acid and coexisting ions during the removal of phosphorus by ion-exchange resin, this study has developed an iron-manganese oxide-modified resin composite adsorbent (Fe/Mn-402) based on the nanoconfinement theory. The structural characterization results of XRD, FT-IR, SEM, and XPS showed that the iron-manganese binary oxide was successfully loaded on the skeleton of the strongly alkaline anion resin and showed good stability under both neutral and alkaline conditions. The batch adsorption experiments showed that the maximum adsorption capacity of Fe/Mn-402 for phosphorus can reach up to 50.97mgg-1 under the optimal raw material ratio (Fe:Mn = 1:1). In addition, Fe/Mn-402 shows good selectivity for phosphorus removal. Fe/Mn-402 can maintain good adsorption performance for phosphate even under high concentrations of SO42-, HCO3-, and humic acid. The regenerated Fe/Mn-402 can be recycled without any obvious change in its treatment capacity. Hence, it is suitable for stable, long-term usage. In general, this work puts forward a new idea for the development of phosphorus-removal adsorbents for the treatment of wastewater containing coexisting ions and HA.

Parallel adsorption of low concentrated ciprofloxacin by a CoFe-LDH modified sludge biochar

The sludge biochar loaded with layered double hydroxides (CoFe-LDH@SBC) was used as a composite adsorbent for removing low concentrated ciprofloxacin (CIP) effectively in water environment. The sludge biochar (SBC) and CoFe-LDH@SBC were synthesized by pyrolysis and self-assembly; and the characterization of SBC and the composite material were analyzed through a series of analytical methods including scanning electron microscopy-Energy Dispersive Spectrometer, X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller, and Zeta potential. Due to various chemisorptions, CoFe-LDH@SBC showed superior adsorption performance for CIP with 14 mg/g, which was 2.8 times of that for SBC. Moreover, Artificial Neural Network (ANN) model was employed to predict the adsorption capacity and removal rate of CIP using experimental data obtained. Furthermore, according to density functional theory (DFT), parallel adsorption was proved to be dominant in the adsorption process, which indicated that the adsorption was a favorable and exothermic chemisorptions process.

Controllable synthesis of porous silicate@carbon heterogeneous composite from Coal Gangue waste as eco-friendly superior scavenger of dyes

Converting naturally abundant Coal Gangue (CG) waste into new materials with special functions or excellent performance has always been desirable. Here, the new porous heterogeneous silicate@carbon composites with high specific surface area of 650.96 m 2 /g (52.88 times of CG), excellent adsorption and removal ability to cationic dyes were synthesized by a controllable one-pot reconstitution reaction process of calcined CG. The optimal composite adsorbent composed of 10.179% Mg and 0.35% carbon can adsorb 269.86 mg/g of Methylene blue (MB) and 504.91 mg/g of Basic Red 14 (BR), which are 29.2 and 28.6 times higher than that of original CG and calcined CG, respectively. The MB and BR dyes in 200 mg/L of the initial dye solution can be removed almost completely after adsorption with 2 g/L of the composite adsorbent, which is significantly superior to raw CG and calcined CG. The dynamic column adsorption curves indicate the adsorption equilibrium was attained at C / C 0 values of 0.78 (for MB adsorption) and 0.75 (for BR adsorption). The used adsorbent can be regenerated and reused for multiple cycles, and the removal efficiency of the adsorbent towards dye is still higher than 90% after 5 regenerations. The adsorption isotherms and adsorption kinetics were studied and the adsorption mechanism was explored. This study demonstrates a feasible way to achieve a sustainable cycle "from waste to environmental purification materials". • Coal Gangue (CG) was converted to synthesize new porous silicate composite adsorbent. • The specific surface area of the adsorbent (650.96 m 2 /g) reaches 52.88 folds of CG. • The adsorbent adsorb 269.86 mg/g of MB and 504.91 mg/g of ABR dye (over 28.6 folds of CG). • Dyes in 200 mg/L of initial solution were almost completely removed by the adsorbent. • The adsorbent shows excellent dye removal efficiency in a dynamic adsorption process.

Compressor-assisted thermochemical sorption integrated with solar photovoltaic-thermal collector for seasonal solar thermal energy storage

• Compressor-assisted thermochemical sorption energy storage with solar PV/T system. • Thermal and electrical energy simultaneously stored in summer, discharged in winter. • Identify the optimal operating condition of solar PV/T coupled with the storage unit. • Chemisorption cycle using SrCl 2 achieves 100% solar fraction for domestic heating. • Higher compression ratio leads to positive effect on the life cycle of PV cells. This paper studied the performance of a compressor-assisted thermochemical sorption energy storage (CATSES) system with a solar photovoltaic-thermal collector (PV/T) to support the domestic space and hot water heating. The heat from the PV/T drives endothermic desorption, whilst the electricity from the PV/T powers the compressor to assist the low-temperature desorption. The main aim of this study was to demonstrate that the integrated system can flexibly and maximally utilise solar energy, and store solar energy in a high energy–density system with minimum loss over long-term storage. The parametric investigation on the CATSES system using SrCl 2 /NH 3 working pair was conducted for a case study in the city of Newcastle upon Tyne in the UK, which has long wintertime with high heating demand. Two different system operation modes (Case 1 and Case 2) with different strategies of solar energy usage (direct usage / storage) were studied. By using 30 m 2 PV/T collector with the CATSES reactor that contains 22 m 3 (450 kg/m 3 ) composite adsorbent and a compressor with 11.5 compression ratio, the system that operated Case 1 could achieve 100% solar fraction of annual heating demand. The achieved material-based energy storage density was around 0.6 GJ/m 3 and the storage efficiency was 0.88 with the net electricity consumption of 180 kWh (around 5% average consumption of an ordinary UK household). The system that operated Case 2 stored less heat than that of the Case 1 but was able to output more electricity.

Efficient and recyclable composite beads containing sodium alginate and EGDMA-AN cross-linked polymer for phenol removal: Kinetic and diffusion mechanisms

Adsorption, a ubiquitous technique used in the purification of pollutants streams, depends on the development of a suitable adsorbent wherein kinetic, equilibrium and diffusion phenomena are crucial aspects to ensure that the separation process will be feasible. Hence, in this study, an accurate isotherm in conjunction with rigorous kinetic and diffusion models was developed to investigate the adsorption mechanisms through independent equilibrium and transient experiments during the adsorption of phenol. To this end, dual cross-linked sodium alginate (SA)/ethylene glycol dimethacrylate (EGDMA) and acrylonitrile (AN) composite beads were prepared using a relatively simple gelation technique. The synthesized SA/EGDMA-AN composite material was characterized by FTIR, SEM-EDS, BET, TGA, XRD and the swelling factor. Additionally, the equilibrium was described by the Freundlich isotherm and the kinetics by the Langmuir model. The diffusion coefficients were found to be in the range 1.54 × 10-7 to 8.75 × 10-8 cm2·min-1 for bead diameters of 2.5 and 4.0 mm, respectively, which represent an effective diffusion behavior of the sorbent molecules. The synthesized SA/EGDMA-AN composite beads can be easily regenerated and separated from an aqueous solution. After regeneration, the SA/EGDMA-AN composite beads still present high adsorption capacity for up to four cycles of desorption and adsorption. These results led us to propose a suitable SA/EGDMA-AN composite adsorbent and a rigorous modeling approximation with good predictive ability that would guide the design of further separation processes for the removal of phenol in wastewater treatment.

Using a Combination of Activated Carbon and Graphene Nanoparticles in a Consolidated Form for Adsorption Ice Maker: A System-Level Modeling

Adsorption refrigeration systems are one of the emerging decarbonization technologies that can use eco-friendly heating sources and working fluids. However, the highly porous adsorbent materials used in these systems have a low thermal conductivity that hinders their system performance enhancement. Graphene nanoplatelets are proposed in the literature to improve the conductive heat transfer through the adsorbent field and the resulting composite adsorbents were favorably testified at the material level. In this study, the impact of employing a composite adsorbent that comprises of 50% activated carbon type Maxsorb III, 40% graphene nanoplatelets, and 10% binder was numerically investigated at a system level. The contradictory effects of heat and mass transfer mechanisms within the composite adsorbent on the performance of an adsorption ice production system were explored for three cases of composite layer thicknesses at different cycle times. The results showed that the maximum specific daily ice production and coefficient of performance of 33.27 kgice·kgads−1·day−1 and 0.3046 were attained at composite thicknesses of 2 and 5 mm and cycle times of 430 and 1230 s, respectively. The higher composite thickness of 10 mm increased the mass transfer resistances, which overlooked the enhancement in the heat transfer and reduced the overall performance.

Evaluating low-cost permeable adsorptive barriers for the removal of benzene from groundwater: Laboratory experiments and numerical modelling

Permeable adsorptive barriers (PABs) consisting of individual (compost, zeolite, and brown coal) and composite (brown coal-compost and zeolite-compost) adsorbents were evaluated for their hydraulic performance and effectiveness in removing aqueous benzene using batch and column experiments. Different adsorption isotherms and kinetic models and different formulations of the equilibrium advection-dispersion equation (ADE) were evaluated for their capabilities to describe the benzene sorption in the media. The batch experiments showed that the adsorption of benzene by the adsorbents was favourable and could be adequately described by the Freundlich and Langmuir isotherms and the pseudo-second-order kinetic model. Particle attrition and structural reorganization occurred in the columns, possibly introducing preferential flow paths and resulting in slight changes in the final hydraulic conductivity values (4.3 × 10−5 cm s−1–1.7 × 10−3 cm s−1) relative to the initial values (4.2 × 10−5 cm s−1–2.14 × 10−3 cm s−1). Despite the fact that preferential flow appeared to have an impact on the performance of the investigated adsorbents, the brown coal-compost mixture proved to be the most effective adsorbent. It significantly delayed benzene breakthrough (R = 29), indicating that it can be applied as a low-cost effective adsorbent in PABs for sustainable remediation of benzene-contaminated groundwater. The formulated transport models could fairly describe the behaviour of benzene in the investigated media under dynamic flow conditions; however, model refinement and additional experimental studies are needed before pilot/full-scale applications to improve the fits and verify the benzene removal processes. Our results generally demonstrate how such studies can be useful in evaluating potential reactive barrier materials.

Chromatographic Purification of Lithium, Vanadium, and Uranium from Seawater Using Organic Composite Adsorbents Composed of Benzo-18-Crown-6 and Benzo-15-Crown-5 Embedded in Highly Porous Silica Beads

The use of the composite adsorbents composed of benzo-15-crown-5 (abbreviated as BC15) and benzo-18-crown-6 (BC18) for the simultaneous recovery of vanadium (V), uranium (U), and lithium (Li) from seawater has been proposed for industrial applications. The adsorption and desorption behavior of these elements on BC15 and BC18 has been examined in various types of aqueous solutions over a wide temperature range. As a result, it was shown that BC15 and BC18 have sufficient adsorption ability for the simultaneous recovery of V, U, and Li from seawater. Moreover, it was seen that the distribution coefficients (Kd) of V decrease with an increase in [HCl]T (subscript T: total concentration), indicating that the anionic V species such as H2V4O134– are exponentially changed into the cationic V species such as V3+, VO2+, and VO2+ under the condition [HCl]T = 1.0 M, and the complexation reactions between BC15 (or BC18) and the initial V structures are inhibited. Besides, it was reasonably shown that the adsorption mechanism is the path through the electrostatic interaction between the anionic V species such as H2V4O134–, and the −C–O–C– single bond that the electron density is eccentrically located in ether functional groups in crown ether rings in BC15 and BC18 (or the −C–OH single bond that the electron density is eccentrically located in bisphenol A in BC15 and BC18). Then, the chromatography experiment of V, U, and Li on BC15 (or BC18) at 298 K was carried out by flowing seawater, 1.0 × 10–2 M HCl, and 1.0 M HCl in sequence. The first peak of V can be separated from the plateau of Li and the first and second peaks of U in the case of the BC15 system. The recovery ratios of V and U were more than 80%. On the other hand, entirely overlapping chromatograms were obtained in the case of the BC18 system, and accordingly, the recovery ratios of V and U were much lower. In short, the separation efficiency of V with BC15 is more pre-eminent than that with BC18. Judging from these results, the durability of BC15 was finally assessed for industrial applications, that is, the aforementioned chromatography experiment was repeatedly carried out to check whether V, U, and Li were stably and mutually separated from seawater or not. The evidence that the recovery performances of V, U, and Li from seawater do not decrease at all after at least five cycle tests was provided. This indicates that this information will be valuable for the development of a practical chromatographic technology to simultaneously recover V, U, and Li from seawater.