Adsorption Capacity Of Adsorbent Research Articles

Improving the removal performance of cadmium from wastewater by phosphate-modified sludge biochar: A mineral dissolution-precipitation perspective

To improve the removal performance of sludge biochar (BC) for heavy metal Cd2+ in wastewater, phosphate-modified sludge biochar (PBC) was prepared by impregnation-pyrolysis. Batch removal experiment was conducted to research the impact of initial solution pH, coexisting ions, contact time, reaction temperatures, and Cd2+ concentrations on the adsorption capacity of adsorbent. The outcome indicated that PBC exhibited excellent Cd2+ removal efficiency at pH 5-7. Compared to the original biochar, phosphate-modified biochar had a stronger resistance to ion interference. The models of pseudo-second-order and Langmuir well described the adsorption processes of Cd2+ on BC and PBC. The maximum adsorption capacities of PBC for Cd2+ were 163.93mg/g, significantly higher than that of BC (72.94mg/g). Adsorption mechanism analysis suggested that Cd2+ removal involved complexation, electrostatic attraction, cation-π interactions, and co-precipitation. According to the semi-quantitative analysis of the mechanism, the leading mechanism for Cd2+ removal by PBC was precipitation (79.94%), whereas the primary mechanisms for Cd2+ removal by BC were complexation (42.57%) and precipitation (48.85%). The strategy of converting highly mobile Cd2+ in aqueous solutions into insoluble cadmium phosphate precipitates using phosphate-modified sludge biochar can be an ideal approach for removing Cd2+ from wastewater.

Emulsion graft polymerization of glycidyl methacrylate onto bamboo fiber composites for efficient removal of lead ions from aqueous solutions

The emulsion graft polymerization process was used to synthesize a novel polyglycidyl methacrylate grafted silanized bamboo fiber composites. The grafting percentage was assessed by varying surfactant, initiator and monomer concentrations. The surface morphologies and thermal behavior of the biocomposites were analyzed using FTIR, SEM, XRD and TGA techniques. In batch adsorption studies, the effect of adsorption parameters like pH, adsorption time, adsorbent dose and solution temperature were examined on the adsorption efficiency of lead ions. The adsorption capacity of biosorbent composites was enhanced through conversion of epoxy group of Poly glycidyl methacrylate (PGMA) into sulfonic acid groups via sulfonation process. The sulfonic acid groups were incorporated into VMBF-g-PGMA by stirring the grafted sample in H2SO4 (98 %) for 2 h at 90 °C to obtain sulfonated grafted polymer (VMBF-g-PGMA-S). By increasing the concentration of monomers up to 5 %, the maximum grafting percentage (289 %) was achieved. The grafting % increases rapidly from 0.5 to 0.20 g initiator and at 0.20 g of initiator, the highest grafting yield was 512 %. The maximum Pb+2 adsorption capacity of adsorbent was 200 mg/g. The thermodynamic parameters for pb+2 adsorption revealed an exothermic and spontaneous nature of sorption process, and the entropy change showed that there are no substantial structural changes occurred in biosorbent material. The experimental results confirmed that sulfonated biosorbent composites are effective, economical, and promising adsorbent which could be used for removal of lead and other ions from aqueous solution.

Capture and removal of nanoplastics using ZIF-derived defective nanoframework: Structure-performance correlation, theoretical calculation and application

Nanoplastics, as a novel pollutant, are widely found in the environment and water, which also can be migrated to vegetables and fruits through irrigation water and the growing process, posing threat to the human health. In this study, post-modification strategy was implemented to synthesize a series of fine-tuning hierarchically porous ZIF-derived nanoframework (Zn-Co-Ni-ZIF, Zn-Co-TA-ZIF and ZIF67-Ni-ZIF) with various morphologies and structures to investigate the relationship between the polystyrene nanoplastics (PS-NPs) adsorption performance and structure property. The correlation degree between PS-NPs adsorption property and structure parameter followed the order of the intensity of Co2p > the intensity of M-N > the number of linker deficiencies > crystal defect > zeta potential. The gray models (GM) (1,1) between adsorption capacity and evaluation items were successfully established (C < 0.342; RSD < 18.108 %) but zeta potential. A highly linked association (R2 = 0.9561) between the PVmeso/PVmicro and equilibrium constants kt2 may be discovered. The combined findings from experimental analysis and Density Functional Theory calculations demonstrated that the adsorption capacity of adsorbents for PS-NPs was greatly enhanced by the introduction of additional defects and the reinforcement of adsorbent-adsorbate interactions, including electrostatic and coordination interactions. Among the selected materials, Zn-Co-ZIF and Zn-Co-Ni-(60 mg)-ZIF exhibited better resistance to acid, alkali, and salt. Moreover, the PS-NPs removal efficiency of Zn-Co-ZIF and Zn-Co-Ni(60 mg)-ZIF were > 83.55 % and > 87.80 %, respectively, in irrigation water, watermelon, strawberry, and carrot, meeting the environmental and food safety. Therefore, this work provides valuable insights into the modification of MOFs to improve the elimination of micropollutants in water, fruit, vegetable, as well as a comprehensive comprehension of the correlations between structure and performance.

Assessing radon adsorption capacity in adsorbents using solid state nuclear track detectors (SSNTDs)

Radon, specifically the isotope 222Rn, poses health risks, particularly in concentrated indoor environments. Recent years have underscored the significance of measuring low radon concentrations outdoors, offering crucial insights into radon priority areas and climate-related processes. To achieve the necessary high sensitivity, one approach involves placing radiation detectors in close proximity to efficient radon adsorbers that function as radiators. While activated charcoal has been employed for over a century, recent years have seen the production of highly efficient synthetic adsorbents and activated carbon materials. A vital parameter essential for designing and modeling sensitive radon detectors/monitors is the adsorption capacity of the adsorbent for radon. This study introduces a simple and cost-effective method enabling the determination of the adsorption capacity of numerous prospective adsorbents simultaneously. The method entails placing SSNTDs in close contact with the adsorbent to generate tracks from the alpha particles emitted by adsorbed 222Rn and its progeny. A theoretical model is presented, facilitating the determination of adsorption capacity using SSNTDs with a well-defined response function to alpha particles. Experimental validation involves comparing theoretical estimates with published data from studies on activated charcoals, demonstrating very good agreement. The method's versatility is underscored by its application to activated carbon fabrics, showcasing its potential to optimize detector designs for enhanced sensitivity. This proposed approach holds promise for advancing radon monitoring technology, contributing to improved risk assessment and environmental studies related to radon.

Chitosan/Graphene oxide/SiO2 Nanoadsorbents for the Removal of Cr(VI) from Wastewaters

The swift industrialization and urbanisation have led to the discharge of significant amounts of hazardous heavy metals into water environments. Heavy metal pollution is currently one of the most significant environmental challenges being addressed, attracting researchers due to its biotoxicity, and non-biodegradability even at minimal concentrations [1]. Chromium (Cr) is among the most prevalent heavy metal contaminants. Its oxidation state, Cr(VI), harms the environment yet has catastrophic consequences for human health [2]. It is removed by physical and chemical procedures such as ion exchange, chemical precipitation and electrochemical treatment. Yet, most of these procedures have downsides, such as the formation of hazardous sludge, causing disposal issues and the need for costly tools and monitoring systems [3]. Adsorption is regarded an appealing and favourable technology because to its ease of design, simplicity, and high efficiency. Carbon-based nanomaterials have been investigated as superior adsorbents in aqueous solutions for the separation of organic and inorganic contaminants. The current study recommends the usage of adsorbents based on graphene oxide (GO). GO is an oxygen-rich material that is produced during the oxidation of graphite. It features hydrophobic areas due to aromatic groups in the nanosheets' centres, along with a large number of hydrophilic functional groups such as hydroxy, aldehyde, epoxy, and carboxyl groups [4]. The latter allow GO to swell and perform electrostatic functions. Chitosan (Cs) is a great adsorbent since it is inexpensive, is biocompatible, and causes no secondary pollution. Its molecular chains include -NH2 and -OH groups, which can interact with heavy metal ions and give significant adsorption capacity [5]. Silicon dioxide (SiO2) nanoparticles with graphene oxide have better physical and chemical characteristics than graphene oxide-like surface area. Similar research has revealed that the presence of SiO2 increases the adsorbent's adsorption capacity for Cr(VI) [6]. The effect of the pH value, contact time and initial chromium concentration was examined in order to determine the feasibility of Cs/GO@SiO2. Its structure and the morphology were studied in detail by the application of BET, XRD, FTIR and SEM techniques. According to the results, the modification of Cs with GO@SiO2 enhanced the percentage removal of chromium ions, especially, in acidic conditions by using 0.5 g/L of the adsorbent. Experimental data of equilibrium were used to calculate adsorption isotherms. According to thermodynamics the spontaneous nature of their adsorption was confirmed. Overall, the results indicate that Cs/GO@SiO2 can be effectively employed for removal of chromium from aqueous solutions.

Two approaches to prepare cationic lignin‐based adsorbents for efficient removal of phosphate ion from wastewater

AbstractIn this work, two types of cationic lignin‐based adsorbents (AL‐METAC and AL‐GTA) were prepared through free radical polymerization or etherification reaction of alkali lignin with 2,3‐epoxypropyl‐3‐trimethylammonium chloride or methylacrylloxyethyl trimethyl ammonium chloride (METAC). The contents of quaternary ammonium groups in the adsorbents were adjusted by changing the dosages of 2,3‐epoxypropyl‐3‐trimethylammonium chloride and METAC to fabricate the adsorbents with excellent adsorption capacity. The structures, aqueous solubility, and physical properties of adsorbents were analyzed. Meanwhile, the effects of adsorbents dosage, pH value of solution, temperature, and ionic strength on the adsorption capacity of adsorbents were also analyzed. These two types of adsorbents exhibited outstanding affinity for phosphate, with a maximum removal efficiency of 51.8 and 73.2 mg/g, respectively. The adsorption processes followed pseudo‐second‐order and Langmuir models well. In addition, the AL‐GTA exhibited higher removal efficiency than AL‐METAC. Moreover, the AL‐METAC and AL‐GTA still retained 69.7% and 69.0% adsorption capacity after four times regeneration. The fabricated lignin‐based adsorbents have potential applications in the removal of phosphate from wastewater, which would promote the high‐value application of lignin.

Investigation on the pore structure-performance relationship of porous carbon adsorbents for SF6/N2 separation via fine pore modulation

The capture and recovery of SF6 as electron specialty gas from SF6/N2 by adsorptive separation have obvious advantages such as the mitigation of greenhouse effect and resource utilization of waste gas. The comprehensive understanding of pore structure-performance relationship of porous materials is beneficial for guiding the design of highly-efficient adsorbents for separating SF6/N2, but is presently limited. In this work, a series of citric acid (CA) and KOH with different molar ratios are designed to synthesize carbon adsorbents denoted as CAK via a one-step carbonization-activation method and probed for the adsorptive separation of SF6/N2. Characterization results reveal that the micropores in carbon adsorbents are finely tuned from 0.73 to 0.88 nm at an angstrom level through increasing the KOH/CA molar ratios in precursors, and the significant mesopores are formed in CAK4. Static adsorption results indicate that the SF6 adsorptive capacity at low pressure of 10 kPa increases and then decreases with the increasing contents of KOH, and the highest value is obtained in CAK2, while the diffusion rates illustrated from the adsorption kinetics continuously increase. By correlating the pore structures with adsorption capacity of adsorbents, the critical role of micropores with size ≤ 0.9 nm in determining the SF6 capacity at 10 kPa and mesopores in enhancing the mass transfer is quantitatively confirmed. The dynamic breakthrough results of CAKx carbon adsorbents for SF6/N2 separation are well explained with these understandings, which are important for guiding the design of porous adsorbents with high-performance for SF6 capture and recovery.

Synthesis of Na-Alginate templated Montmorillonite-Silica Composite as adsorbent for removal of Rhodamine B

In this study, mesoporous Montmorillonite-Silica composites prepared by using different amount Alginate as sacrificial template, for removal of Rhodamine B is investigated. By alternating Alginate amount it is aimed to switch the porosity of adsorbents thus the adsorption capacities of adsorbents. Synthesized adsorbents had been characterized by using Scanning Electron Microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and N2-Ads/Des techniques. It is observed that beside the decrease in the micropore volume, the total pore volume of the adsorbents increased with the increasing of used Alginate amount. The total pore volumes of adsorbents synthesized with different Clay/Alginate ratio (10, 5, 1) were found as 0.116, 0.172, and 0.178 cm3/g, respectively. Batch adsorption studies showed that the maximum removal efficiencies were obtained at acidic conditions and the adsorbents had better fit with Freundlich isotherm. Qm values obtained from Langmuir isotherm were found as 24.47, 31.97 and 28.48 mg/g for synthesized adsorbents. Also, adsorption kinetic studies showed that for all adsorbents, experimental data had good fit to the pseudo-second order kinetics model. The model parameters were found as 5.9,6.3 and 6.5 (10–3 g/ (mg min). Thermodynamic parameters were also investigated in the study. Negative ∆Go values pointed out that the adsorption of RhB onto synthesized adsorbents was favorable process. Positive values of ∆Ho and ΔS indicated that the adsorption of RhB on adsorbents were endothermic and rising of randomness during the adsorption of RhB on the surface of the adsorbent. Adsorbents could be recovered at least five times without significant decrease in adsorption capacity.

Adsorption of cadmium and copper using biochar obtained from the residue of the second-generation ethanol production: kinetics and equilibrium study

The disposal of industrial effluents containing cadmium and copper ions is a significant environmental concern. This study aims to address this issue by evaluating the adsorption capacity of adsorbents derived from residual biomass from second-generation ethanol production. The objective is to effectively remove cadmium and copper ions from aqueous solutions. The biochar utilized in the study was characterized as microporous and exhibited characteristic bands associated with carboxyls and hydroxyls. The pHPZC (point of zero charge) was determined to be 8.0. The kinetic study revealed that the PSO (pseudo-second-order) model provided the best fit, indicating that the adsorption rate depends on the amount of solute adsorbed onto the adsorbent’s surface. In the equilibrium study, it was observed that adsorption occurred in a monolayer, as evidenced by the superior fit of the Langmuir model. Furthermore, the equilibrium experimental data for the bicomponent system was more accurately represented by the empirical models of Extended Freundlich and Modified Redlich-Peterson. These findings demonstrate the potential of biochar derived from the residue of second-generation ethanol production, a novel application, in effectively removing cadmium and copper ions from aqueous solutions.

Modeling of multi-temperature Type I and II benzene/ammonia adsorption isotherms: Dual LF model and linearized DR model

Adsorption isotherm is basic data for evaluating the porous adsorbent adsorption capacity and explaining gas–solid adsorption behavior. Adsorption equilibrium modeling is a simple method to describe isotherm data in application. In this paper, taking C6H6 and NH3 as an example, multi-temperature Type I or Type II adsorption isotherms on AC, ASZMT, and 13X were investigated and fitted. Results show that C6H6 and NH3 adsorption behaviors on 13X both existed in chemisorption. At certain adsorbed capacity, the isosteric heats are higher than 50 kJ·mol−1. Type I and Type II C6H6 or NH3 adsorption isotherms could be successfully described using the extended Dual LF model·NH3 temperature-independent characteristic curves on AC and ASZMT were obtained using the Linearized DR model and successfully used to predict NH3 adsorption data at any pressure within the whole room temperature. Further, the Dual LF model was extended to describe other adsorption isotherms including IUPAC Type III, IV, and V. The R2 between the model and data were higher than 0.98, proving that it has universal applicability than other classical models such as Langmuir, Freundlich, Toth, and so on. It has the potential to be used as a general equilibrium model for adsorption process simulation in the future.

Experimental investigation for enhancement of heat and mass transfer during regeneration of zeolite 13X-water pair

The effect of adding metal pieces in the adsorbent bed for enhancing the effective thermal conductivity and drying kinetics is investigated for the Zeolite 13X bed. Aluminum, stainless-steel pieces ranging in size from 1.5 cm to 2 cm, and aluminum oxide nanoparticles are chosen, and the total weight added to the bed is approximately 2 % of the adsorbent weight. The different semi-theoretical drying models like Lewis, Page, Logarithmic, Henderson, and Pabis and empirical models like Weibull and Gaussian model are used for the analysis. Adsorption and desorption of Zeolite 13X-water integrated with various metal pieces revealed a decrease in the adsorption capacity of adsorbents with metal pieces and increased bed moisture content for powdered aluminum oxide. It can be noticed that the desorption process was improved by including the metal pieces in the adsorbent bed.; Desorption rates range from 19.54 % for the bed mixed with straight aluminum pieces and 21.43 % for the bed filled with stainless steel. The desorption rates for the bed containing nanoparticles of aluminum oxide and spiral aluminum pieces are 20.48 % and 22.21 %, respectively. The experimental investigation on efficiency enhancement revealed that the desorption process of an adsorbent bed with straight aluminum pieces increased efficiency by 12.38 %, while the bed with aluminum oxide and stainless steel increased efficiency by 17.75 % and 23.20 %, respectively. The effectiveness of an adsorbent bed with spiral aluminum pieces is enhanced by 27.68 %. The drying kinetics analysis of zeolite 13x regeneration using semi-theoretical and empirical models which showed good agreement with experimental results.

Efficient dye adsorption of mesoporous activated carbon from bamboo parenchyma cells by phosphoric acid activation.

In order to solve the environmental damage caused by the discharge of dyes as industrial wastewater, the development of efficient and sustainable adsorbents is the key, while most of the previous studies on bamboo parenchyma cells have focused on their microstructural, functional and mechanical properties, and few of the properties in adsorption have been investigated. To evaluate the role of the unique microstructure of bamboo parenchyma cells on adsorption after carbonization and activation, PC-based activated carbon (PPAC) was fabricated by the phosphoric acid activation method and tested for adsorption using methylene blue (MB). The effect of mesoporous structure on MB adsorption was investigated in detail using PPAC-30C impregnated with phosphoric acid at a concentration of 30%. The results showed that the adsorption performance was influenced by single-factor experiments (e.g., pH, activated carbon dosing). The adsorption isotherms and kinetics could conform to the Langmuir model (R2 = 0.983-0.994) and pseudo-second-order kinetic model (R2 = 0.822-0.991) respectively, and the maximum MB adsorption capacity of adsorbent was 576 mg g-1. The adsorption mechanism of MB on PPAC-30C includes physical adsorption, electrostatic attraction, hydrogen bonding, and the π-π conjugation effect, which was dominated by physical adsorption. The results of this study show that PPAC has good application prospects for cationic dye removal.

Removal of Ibuprofen and Diclofenac using Azadirachta indica leaves extract modified with Iron oxide

Plant-based adsorbents have the potential to replace commonly used chemical adsorbents due to their cost effectiveness, eco-friendly and non-toxic properties. In this study, the adsorption potential of green synthesized iron-oxide particles, using neem (Azadirachta indica) leaves extract, was evaluated as a novel adsorbent for the removal of ibuprofen and diclofenac. The optimization of treatment factors for experimental design was undertaken via the Taguchi method. The adsorbent’s characterization was performed by the employment of Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy. Four adsorption factors were kept under consideration during experimental runs for each drug; initial concentration (10–40 ppm), contact time (10–40 min), pH level (3–9), and adsorbent dosage (0.1–0.4 g/L). Maximum removal efficiency as indicated by the results, was 81.89% for ibuprofen and 80.82% for diclofenac, achieved at optimum conditions of pH 5, 40 ppm initial concentration, 40 min contact time, and 0.3 g/L adsorbent dose. Among the adsorption factors, pH and initial concentration were observed to exert the greatest influence on the removal efficiencies for both drugs. The maximum adsorption capacity of adsorbent was 81.96 mg/g and 81.46 mg/g for diclofenac and ibuprofen, respectively. Freundlich isotherm fitted best to the removal both pharmaceutical compounds. The adsorbent used in this study demonstrated significantly higher removal potential and adsorption capacity for diclofenac and ibuprofen as compared with previously used adsorbents.

Sustainable removal of hexavalent chromium using graphene oxide - Iron oxide reinforced pectin/polyvinyl alcohol magnetic gel beads

The study investigated removal of hexavalent chromium Cr (VI) from aqueous solution using graphene oxide‑iron oxide reinforced pectin/polyvinyl alcohol magnetic gel beads prepared through co-precipitation and freeze-drying technique. Scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer, N2 adsorption-desorption isotherm, and zeta potential are used for characterization. The surface area of magnetic gel beads calculated by BET method was determined to be 100.95 m2/g, significantly higher than that of GO and GO-Fe3O4. The optimum removal efficiency of GO-Fe3O4/Pec/PVA was assessed by batch method at variables such as pH(1–6), adsorption time(0–180 min), and temperature(25–35 °C). Accordingly, 0.2 g GO-Fe3O4/Pec/PVA dose, pH 2, contact time: 120 min at 25 °C were found to be the optimal conditions, and maximum adsorption capacity of GO, GO-Fe3O4 and GO-Fe3O4/Pec/PVA toward Cr(VI) removal was found to be 39.5, 62.5 and 78.55 mg g−1, respectively. Kinetic and isotherm studies indicate adsorption data follow pseudo-second-order kinetic and Langmuir isotherm models. Thermodynamic studies showed adsorption capacities of adsorbents decreased when temperature increased which indicated adsorption for Cr (VI) was an exothermic process. The activation energies were found to be 34.92, 26.57, and 35.23 KJ mol−1 for GO, GO-Fe3O4, and GO-Fe3O4/Pec/PVA, respectively, which illustrated adsorption of Cr(VI) onto the surface of adsorbents was a physical process. The beads exhibit excellent recoverability and reusability over five cycles. Overall, GO-Fe3O4/Pec/PVA demonstrates exceptional adsorption properties and can serve as an efficient, stable, less toxic, and magnetically separable adsorbent for removal of Cr(VI) from aqueous solution.

Electrospinning prepared nickel-based carbon fibers with enhanced adsorption capacity for adsorption desulfurization of fuels

Enhanced adsorption capacity of adsorbents with excellent regeneration properties always remained the focus of researchers in the adsorptive desulfurization (ADS) technology. In this paper, we report an electrospinning method to prepare nickel-based carbon fibers (NCF), and their adsorption desulfurization performance was compared with those of nickel-based carbon particles (NCP) obtained via traditional solid-state grinding method. The results demonstrated that compared with NCP, NCF contained more abundant mesoporous specific surface area and mesopore volume, well-distributed active metal sites, which would be beneficial to their enhanced adsorption desulfurization performance. As a result, the adsorption capacity of NCF was as high as 13.13 mg S/g in the ADS of thiophene, and its regeneration performance was also far better than that of NCP. In addition, the adsorption process of thiophene was briefly analyzed from the perspective of kinetics, which demonstrated that the adsorption of thiophene in NCF and NCP were both in accordance with the pseudo-second-order kinetic model.

Ultrasound-assisted adsorption of organic dyes in real water samples using zirconium (IV)-based metal-organic frameworks UiO-66-NH2 as an adsorbent

The utilization of dye adsorption through metal-organic frameworks represents an eco-friendly and highly effective approach in real water treatment. Here, ultrasound assisted adsorption approach was employed for the remediation of three dyes including methylene blue (MB), malachite green (MG), and congo red (CR) from real water samples using zirconium(IV)-based adsorbent (UiO-66-NH2). The adsorbent was characterized for structural, elemental, thermal and morphological features through XRD, XPS, FTIR, thermogravimetric analysis, SEM, BET , and Raman spectroscopy. The adsorption capacity of adsorbent to uptake the pollutants in aqueous solutions was investigated under different experimental conditions such as amount of UiO-66-NH2 at various contact durations, temperatures, pH levels, and initial dye loading amounts. The maximum removal of dyes under optimal conditions was found to be 938, 587, and 623 mg g−1 towardMB, MG, and CR, respectively. The adsorption of the studied dyes on the adsorbent surface was found to be a monolayer and endothermic process. The probable mechanism for the adsorption was chemisorption and follows pseudo-second-order kinetics. From the findings of regeneration studies, it was deduced that the adsorbent can be effectively used for three consecutive cycles without any momentous loss in its adsorption efficacy. Furthermore, UiO-66-NH2 with ultrasound-assisted adsorption might help to safeguard the environment and to develop new strategies for sustainability of natural resources.

New biobased chitosan/polyvinyl alcohol/graphene oxide derivatives for the removal of pharmaceutical compounds from aqueous mixtures

The main scope of this study is synthesis, characterization and implementation of new bio-based chitosan derivatives for the removal by adsorption of pharmaceutical mixtures from aqueous matrices. Six different materials of chitosan/polyvinyl alcohol were synthesized using an increasing quantity of graphene oxide and reduced graphene oxide (0.05%, 0.1% and 0.2%). A combination of different groups of pharmaceuticals was used as a model pollutant. Within this context, four non-steroidal anti-inflammatory drugs (diclofenac, ibuprofen, ketoprofen, paracetamol), one anti-epileptic (carbamazepine) and two antihypertensives (valsartan and irbesartan) were selected. The highest adsorption capacity was exhibited by the composites with the highest concentration of GO and rGO (0.2%), while the pollutants that presented the highest adsorption removal were valsartan and diclofenac. The adsorption process was appeared to be finished after 3 h for all compounds of the studied mixture (well-fitted to pseudo-2nd order model). The results indicated that the Langmuir model offered better match for the experimental data, while the adsorption capacity of adsorbents increased with the rise of the temperature. Overall, the highest adsorption capacities achieved at pH 10 (55 °C). Desorption was accomplished by using different aqueous eluents (with pH 2–10) and organic solvents. FTIR, SEM, EDS techniques were used to characterize the composition and morphology, and for the compounds detection the UHPLC system was used.

CO2-assisted synthesis of graphitic resin-based activated carbon for ultrahigh selective adsorption of VOCs under humid conditions

Water vapor in the waste gases greatly reduce the VOCs adsorption capacity of adsorbents due to the competitive adsorption. Though chemical activation combined with catalytic graphitization was an available strategy for achieving both good graphitization and rich porosity to capture VOCs under humid conditions, it still remains a challenge of catalyst deactivation. This work developed a novel route to synthesize graphitic resin-based activated carbon (GRC) via CO2-assisted Fe-catalyzed graphitization and concurrent KOH activation. The selective adsorption behaviors of VOCs/water vapor were thoroughly investigated by static and dynamic adsorption experiments. The obtained GRC-10-A (5) displayed an outstanding graphitization degree, lower O content and hierarchical pore structure. This triggers a high dynamic adsorption capacity and a faster intra-particle diffusion both for toluene and 1,2-dichloroethane. For weak polar toluene, the adsorption selectivity quantized by Difference of Isosteric Heats equation was up to 69, exceeding strong polar 1,2-dichloroethane up to 12. Grand Canonical Monte Carlo simulations were used to explore the competitive adsorption mechanism from the perspective of surface oxygen groups (SOG) and pore size. The results revealed the main contributor to the excellent adsorption selectivity was a lower SOG content, which restricted the formation and pore condensation of water clusters. On the other hand, both the micropore overlap potential and molecular kinetic diameter determined the advantageous pore size ranges for different VOCs under humid conditions. These findings provide support for the fabrication and practical application of adsorbents in VOCs removal from humid conditions.

Adsorption of CO2 on Activated Carbon, Fe‐Based Metal Organic Framework, ZnO, and CaO for Carbon Capture and Storage Application

AbstractActivated carbon (AC) from coconut shell, iron‐based metal organic framework (Fe‐MOF), zinc oxide (ZnO), and calcium oxide (CaO) were prepared as adsorbents for the CO2 adsorption process. The adsorption experiments were performed in a self‐designed fixed‐bed small reactor to study the influence of reaction conditions on the CO2 adsorption capacity of adsorbents. According to the findings, Fe‐MOF showed better performance in CO2 adsorption compared to the other selected adsorbents. The results were supported by the high surface area of Fe‐MOF, which was greater than that of AC, ZnO, and CaO. The optimal parameters for CO2 adsorption of all adsorbents were determined in terms of adsorbent dosage, operating pressure, and CO2 adsorption time.

Decrease in the Adsorption Capacity of Adsorbents in the High-Temperature Carbonate Loop Process for CO2 Capture

In this study, the sorption capacity of limestone samples for CO2 was investigated to determine the conditions under which they can be used in the high-temperature carbonate loop process. For the work, limestone samples from the Czech Republic were used, which contained a high proportion of CaO (more than 97 wt.%). A total of 20 cycles of calcination (950 °C) and subsequent CO2 sorption–carbonation (650 °C) were performed for each limestone sample tested. The sorption capacity towards CO2 in the 20th cycle was less than 10% of the value determined in the first carbonation cycle of the samples and the most significant decrease was observed between the first and second cycles. The highest sorption capacity was determined for the Branžovy sample, which captured 268 mL of CO2/per 1 g of sorbent by chemisorption. Only 15 mL of carbon dioxide per 1 g of sorbent was bound by physisorption. However, in repeated use, the Vitošov limestone had the highest sorption capacity for CO2. For all samples, the amount of carbon dioxide bound by physisorption was in the range of 4 to 10% of the amount bound by chemisorption. Due to sintering of the material, the BET specific surface area decreased by 95 to 96%.