Single Adsorption Research Articles

Optimization of ciprofloxacin removal by response surface methodology using activated carbon from Burmese grape obtained from Vietnam

Activated carbon is produced from Burmese grapes using NaOH as the activator under microwave irradiation. Through scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction analysis, and Brunauer–Emmett–Teller analysis methods, the activated carbon material is found to have a rough and uneven surface with the formation of pores, an amorphous structure, and possesses hydroxy, C–H, carbonyl, alkene, and ether functional groups. The surface area (478.5 m2 g−1) and pore size (about 3.4 nm) are calculated from the adsorption N2equation. The adsorption mechanism of activated carbon is evaluated and follows a pseudo-first-order kinetic model (large single adsorption) and the Langmuir isotherm model (physical interaction). The factors affecting ciprofloxacin adsorption using activated carbon derived from Burmese grapes are also evaluated and optimized by the response surface method model based on influencing factors including the contact time, the solution pH, the antibiotic concentration, and the material dosage. The optimal parameters are as follows: pH = 6.26, concentration = 58.9 mg L−1, content = 0.15 g L−1, time = 54 min. Under optimal conditions, the adsorption capacity predicted from the model is 191.33 mg g−1with an efficiency of 41.35%.

Raphanus caudatus biomass powder as potential adsorbent for the removal of crystal violet and Rhodamine B dye from wastewater

Abstract In this work, Raphanus caudatus (radish pod) leaves biomass was used as an adsorbent for the removal of crystal violet (CV) and Rhodamine B (RhB) dye from water medium. Adsorption process was performed by changing different adsorption factors such as adsorbent dose, agitation time, adsorbate concentration, pH and temperature to get maximum removal of dyes. It was observed that R. caudatus leaves biomass showed 48.7 and 19.0 mg/g value of adsorption capacity for CV and RhB dyes, respectively. High adsorption capacity value for CV was observed due to its less complex structure and small sized molecules as compared to the RhB dye molecules. Dyes removal process followed pseudo second order with the values of regression factor (R 2) found as 0.999 and 0.998 for CV and RhB, respectively. Values of R 2 were found as 0.999 and 0.998 for the removal of CV and RhB respectively while following the Langmuir adsorption isotherm model. It illustrates the single layered dye molecules adsorption over the homogeneous surface of the adsorbent. Value of enthalpy (ΔH°) was found as 11.983 and 12.28 kJ/mol for CV and RhB, respectively. It indicates endothermic nature of the process along with the increased entropy at the surface of the adsorbent during the process. Increase of salt concentration in adsorption medium caused the decreased percentage removal of dyes. Reported adsorbent also showed potential for the removal of toxic dyes from industrial wastewater.

Europium adsorption by granulated Cr-MIL-PMIDA metal−organic frameworks and dynamic fixed bed column modelling

Cr-MIL-PMIDA adsorbent exhibits high selectivity for Rare Earth Elements (REE) over competing transitional metals. However, shaping of this highly efficient material is necessary for industrial applications. Therefore, this paper focuses on the treatment of mining wastewater using a dynamic column adsorption process. In this study, Cr-MIL-PMIDA was successfully granulated for the first time using alginic acid and CaCl2. Divalent calcium ions (Ca2+) acts as the cross-linking agent with carboxyl groups, enabling the encapsulation of Cr-MIL-PMIDA powder and controlled release. The prepared material was characterised using XRD, SEM and FTIR measurements to validate successful granulation. Adsorption capacity of powdered Cr-MIL-PMIDA of 56.01 mg/g decreased to 31.05 mg/g after granulation due to reduction of surface area and pore volume. However, granulated Cr-MIL-PMIDA recorded only an 8 % reduction in selectivity towards Eu in a multi component solution compared to the powdered state. The material exhibited the ability to be reused for five cycles while maintaining over 90 % of its initial adsorption capacity. Furthermore, this study demonstrates that the dynamic column model developed for a novel granulated Cr-MIL-PMIDA can be reliably utilized to design industrial-scale systems for resource recovery from mining wastewater with a single adsorption column experiment.

The effects of chlorine-containing species on cinnabar: A density functional theory investigation into the surface adsorption reactivity of mercury sulfide

First-principles computations can be used to noninvasively probe semiconductor surfaces and describe mechanisms and transformations that occur on those surfaces. One such material of interest is the chalcogenide mercury sulfide (HgS), also known as cinnabar. Cinnabar (α-HgS) and its synthetic counterpart (vermilion) have been used as bright red pigments since antiquity and are important sulfide materials in the field of art conservation. However, it has been known since Roman times that these pigments can darken when exposed to light. It has been hypothesized that Cl2 and other chlorine-containing materials are involved in the photodegradation of cinnabar surfaces. Here we use first-principles density functional theory (DFT) to probe the adsorption reactivity of Cl-containing adsorbates on HgS surfaces, as DFT yields information at the atomistic level and can link changes in surface structure to changes in electronic states. Specifically, we model single adsorbates interacting with corrugated and flat HgS surfaces to probe the initial step in the photodegradation mechanism. This allows us to not only assess the strength of adsorption and any corresponding adsorbate dissociations, but also link these adsorption and dissociation events to key changes in the electronic band structure that may act as spectroscopic identifiers in the degradation pathway of chalcogenide semiconductors that contain photoreactive metals.

Removal of ciprofloxacin lactate by phosphoric acid activated biochar: Urgent consideration of new antibiotics for human health

The long-term accumulation and residue of the emerging pollutant ciprofloxacin lactate (CIP) in the aquatic environment have caused great harm to the ecological environment. In this experiment, CIP was adsorbed on H3PO4-activated cow dung biochar (PBC) prepared with different impregnation ratios. It was found that the secondary pyrolysis of activated original biochar leads to more thorough carbonization, increased aromaticity, hydrophobicity, increased porosity, and increased hydroxyl, carboxyl, carbonyl and a large number of functional groups. When pH value was 5.0, 30P-BC had the highest adsorption capacity. The fitting correlation of PSO models for BC, 10P-BC, 30P-BC, and 50P-BC is higher, with the correlation coefficients of 0.9930, 0.9917, 0.9874, and 0.9886, respectively. The maximum adsorption capacity of materials were 15.27 mg/g (BC), 39.97 mg/g (10P-BC), 53.89 mg/g (30P-BC) and 22.04 mg/g (50P-BC), respectively. The four adsorbents are dominated by single molecule layer chemical adsorption, and there is also a physical adsorption process. The primary mechanism of CIP is the interaction between pore filling and π-π electron donor acceptor, which also includes electrostatic and hydrogen bonding. The removal efficiency applied to actual wastewater and the health assessment of human health risks are worth considering. The removal rate of CIP by 30P-BC in the simulated wastewater experiment reached 97.77 %. Moreover, through the model fitting of the polluted water quality contribution rate to human health exposure, the removal of CIP by 30P-BC can greatly reduce the related risks to human health.

Graph Transformer with Convolution Parallel Networks for Predicting Single and Binary Component Adsorption Performance of Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) are considered one of the most important materials for carbon capture and storage (CCS) due to the advantages of porosity, multifunction, diverse structure, and controllable chemical composition. With the continuous development of artificial intelligence (AI) technology, more and more machine learning models are used to identify MOFs with high performance within a massive search space. However, current works have yet to form a model that uses graph-structured data only, which can predict the adsorption properties of single and binary components. In this work, we proposed and developed a graph transformer, combined with convolution parallel networks, called GC-Trans. The model can accurately and efficiently predict the adsorption performance of MOFs under the single- and binary-component adsorption conditions using only the features of the crystal diagram as inputs. By extracting and fusing local and global feature information, the model has stronger expression and generalization abilities. Thus, we used it to screen the ARC-MOF database and analyze the MOF structures that meet the target requirements. Additionally, to demonstrate the transferability of the model, we applied transfer learning methods to predict the CO2/CH4 separations and CH4 uptake, both of which showed good predictive performance.

High-affinity fluoride ions absorbent from TiO2-based ionic liquid pyridinium propylsulfonate

The development of materials for high efficiency removal of fluoride ions (F-) from sewage water remains a significant challenge. Unfortunately, traditional metal oxide adsorbents remove F-, but suffer from poor adsorption capacity and generate secondary pollution due to byproducts. To solve this problem, a highly-efficient and recyclable F- adsorbent with rich pore structure (BET specific surface area of 172.15 m2·g−1) was developed by multi-element doping strategy. The F- adsorbent was composed of TiO2 as substrate and ionic liquid pyridinium propylsulfonate as doping. This absorbent displayed good F- adsorption capacity (qmax = 224.11 mg∙g−1, 298 K), which operated through single molecule complex adsorption mechanism, outperformed many commercial adsorbents, and it also exhibited satisfactory adsorption kinetics for improving the efficiency of water treatment. Interestingly, the porous adsorbent had excellent regeneration potential (maintaining more than 70 % F- removal efficiency after 5 cycles of adsorption and desorption) and practical ability in complex water environments of tap water, lake and river. More importantly, a fixed-bed for F- adsorption was designed to simulate the equipment of sewage treatment plant. The breakthrough time and saturation time obtained by fixed-bed experiments proved the practical application value of this novel adsorbent. Most strikingly, the cost estimate showed that the economic feasibility and practical promotion potential of the renewable, continuous and efficient F- wastewater purification system using the novel absorbent were remarkable. This innovative approach showcases a viable solution for addressing F- removal and water treatment.

Highlighting the single and binary adsorption mechanism of amoxicillin and doripenem on copper benzene-1,3,5-tricarboxylate MOF via experiments, characterization, statistical physics modelling and DFT simulation

Highlighting the single and binary adsorption mechanism of amoxicillin and doripenem on copper benzene-1,3,5-tricarboxylate MOF via experiments, characterization, statistical physics modelling and DFT simulation

Exploring the simultaneous mass transport of nimesulide and paracetamol adsorption on activated carbon: A PVSDM approach

Pore Volume and Surface Diffusion Model (PVSDM) was advanced to Extended PVSDM for modeling multicomponent adsorption systems. The dynamic adsorption of nimesulide and paracetamol on activated carbon was investigated through single and binary adsorption experiments. Langmuir and Extended Langmuir isotherms were used as local equilibrium functions, respectively. The results reveal that single and binary adsorption were affected by both external mass transport and intraparticle diffusion. The coexistence of nimesulide and paracetamol led to a competitive adsorption phenomenon, wherein nimesulide exhibited a higher affinity for the activated carbon surface, primarily occupying its surface active sites, while paracetamol diffuse into the pore volume to be adsorbed, especially at higher initial pharmaceutical concentrations. These findings emphasize the necessity of employing the robust Extended PVSDM for predicting the complex dynamics of binary adsorption. The findings also provide valuable insights that can significantly contribute to the development of efficient adsorption processes, addressing urgent environmental challenges.

Removal of Ni(II), Cu(II), Pb(II), and Cd(II) from Aqueous Phases by Silver Nanoparticles and Magnetic Nanoparticles/Nanocomposites.

The intake of heavy metals into the body, even at very low concentrations, may cause a decrease in central nervous system functions; deterioration of blood composition; and liver, kidney, and lung damage. Therefore, heavy metal ions must be removed from water. In this study, silver, magnetic iron/copper, and iron oxide nanoparticles were synthesized using Lathyrus brachypterus extract and then Fe/Cu-AT, Fe3O4-AT, Fe/Cu-CS, and Fe3O4-CS magnetic nanocomposite beads were synthesized using alginate and chitosan. The removal of Cd(II), Pb(II), Ni(II), and Cu(II) ions from aqueous phases using synthesized nanoadsorbents was investigated by single and competitive (double and quaternary) adsorption techniques. The kinetic usability of the magnetic iron oxide chitosan (Fe3O4-CS) nanocomposite beads with the highest removal efficiency was evaluated. Based on experimental results, the order of removal was found to be 98.39, 75.52, 51.54, and 45.34%, and it was listed as Pb(II) > Cu(II) > Cd(II) > Ni(II), respectively. The Dubinin-Radushkevich, Freundlich, Langmuir, and Temkin isotherm models were used, and experimental results revealed that the experimental data fit the Langmuir model better. The maximum adsorption capacities (qm) obtained from the Langmuir isotherm model of Fe3O4-CS were found to be 8.71, 23.75, 18.57, and 12.38 mg/g for Ni(II), Pb(II), Cu(II), and Cd(II) ions, respectively. When the kinetic data were applied to the Lagergren, Ho-McKay, and Elovich models, it was observed that the adsorption kinetics mostly conformed to the Ho-McKay second-order rate equation. The binary and quaternary competitive adsorption data showed that Fe3O4-CS were selective toward Cu(II) and Pb(II). The reusability of the Fe3O4-CS nanoadsorbent was performed as three cycles with the same concentration. The adsorption capacities were found to be 95.81, 70.65, 50.50, and 42.75%, in turn for Pb(II), Cu(II), Cd(II), and Ni(II) ions after three cycles, which revealed that the Fe3O4-CS nanoadsorbent can be used after three cycles without losing its efficiency.

Investigation of adsorption performance of calcium oxide particles upon various treatments.

This study describes the improvements of adsorption capacities for raw calcium oxide (CaO) particles subjected to ultrasonication, activation with nitric acid and thermal treatments. The influence of acids and bases on CaO particle surface was assessed with respect to several variables including treatment methods, adsorption contact times, particle size and specific surface area characteristics, concentration and temperature along with various thermodynamic parameters. Structural analyses and physical characteristics of CaO particles were evaluated using FT-IR and SEM methods. SEM micrographs of samples revealed uniform distributions of CaO particles of average diameter 0.5-2.0µm. The CaO surfaces showed CH3COOH as having the greatest amounts of adsorbate and modeling of the experimental adsorption isotherm data agreed well with the Freundlich adsorption isotherm. Enhancements in adsorption performance of untreated CaO particles were noted with the ultrasonication, activation with HNO3 and thermal treatment processes. The Langmuir-type adsorption demonstrated that single layer adsorption capacities of adsorbate CH3COOH at 25oC on sonicated CaO (386.6mg/g), with nitric acid and thermal activation (354.9 and 320.8mg/g, respectively) were greater than that of the unsonicated CaO (296.3mg/g) particles. Adsorption spontaneities of the processes were confirmed by the decreases in adsorption free energy values, ΔGads0, changing from -16.1 to -17.1kJmol-1 with temperature range 283-338K.

Density functional theory study of NO adsorption on the transition metal M (M=Cu, Fe and Mn) modified TiO2 surface

To study the effect of different kinds of transition metals and their proportions on NO adsorption on TiO2 surface, the density functional theory (DFT) method was used to calculate the energetic, geometric structure and electronic structure of the adsorption of NO on transition metal M (M = Cu, Fe and Mn)-anatase TiO2 (101) surface. The above transition metals were adsorbed on anatase TiO2 (101) surface in three different adsorption ratios, which are single transition metal adsorption model, mixed 2:2 and 1:3 ratio models. On the basis of the study, 13 models were established to study the effects of transition metals and adsorption ratio on NO oxidation to determine the optimal adsorption model. It has been found from the energetic calculations that mixed adsorption model is more stable for the adsorption of NO. The results of electronic structure and charge distribution analysis showed that a large quantity of active electron clusters are distributed around Mn and Fe atoms, which are attached to a large area of N atoms in NO, indicating that Mn and Fe can provide more electrons for catalytic reaction and facilitate electron exchange between catalyst and NO. Among all the adsorption models, the 3Fe+1Mn–TiO2 and 3Mn+1Fe–TiO2 models are superior, i.e., they can exchange more electrons with NO before the catalytic reaction, which is conducive to the subsequent catalytic reaction.

Coexisting ions and long-chain per- and polyfluoroalkyl substances (PFAS) inhibit the adsorption of short-chain PFAS by granular activated carbon

We assessed the competitive adsorption between long-chain and short-chain PFAS and the impact of coexisting ions to understand the mechanisms leading to the early breakthrough of short-chain PFAS from granular activated carbon (GAC) filters. Three pairs of short-chain and long-chain PFAS representing different functional groups were studied using GAC (Filtrasorb 400) in batch systems. In bisolute systems, the presence of long-chain PFAS decreased the adsorption of short-chain PFAS by 30–50% compared to their single solute adsorption capacity (0.22–0.31 mmol/g). In contrast to the partial decrease observed in bisolute systems, the addition of long-chain PFAS to GAC pre-equilibrated with short-chain PFAS completely desorbed all short-chain PFAS from GAC. This suggested that the outermost adsorption sites on GAC were preferentially occupied by short-chain PFAS in the absence of competition but were prone to displacement by long-chain PFAS. The presence of inorganic/organic ions inhibited the adsorption of short-chain PFAS (up to 60%) but had little to no impact on long-chain PFAS, with the inhibitory trend inversely correlated with Kow values. Study results indicated that the displacement of short-chain PFAS by long-chain PFAS and charge neutralization are important mechanisms contributing to the early breakthrough of short-chain PFAS from GAC systems.

Experimental and numerical analysis of oily wastewater treatment using low-cost mineral adsorbent in a single and multi-fixed bed column

In this research, single and multi-bed adsorption columns for oily wastewater treatment were investigated both experimentally and numerically. For this purpose, two mineral adsorbents, namely natural zeolite and calcined bentonite, were used. The adsorbent characteristics were analyzed by XRD, BET, and SEM. Adsorption isotherm and single fixed-bed adsorption column performance for both adsorbents were experimentally assessed at different concentrations. In addition, single- and multi-fixed-bed column applicability with two different configurations, series and parallel connections, were simulated. The experimental results showed that Freundlich and Langmuir isotherms had the best performance to describe the adsorption of calcined bentonite and natural zeolite, respectively. Moreover, natural zeolite has better performance for oily wastewater treatment than calcined bentonite. The maximum capacity of calcined bentonite and natural zeolite was obtained at 3.06 mg/g and 5.37 mg/g, respectively. The simulation results indicated that the maximum separation yields of single fixed-bed, multi-fixed-bed with series connections, and multi-fixed-bed with parallel connections were 39.3%, 99.98% and 74.58%, respectively. Adsorbent mass optimization indicated that the required adsorbent mass decreased by 33.1% when four beds were presented in an operation instead of a single bed. This research recommends a promising application of natural zeolite as an economic adsorbent in multi-bed adsorbers for oily wastewater treatment.

Molecularly imprinted composite membranes with interleaved imprinted network structure for highly selective separation of acteoside

Acteoside (ACT) is one of the phenylethanoid glycosides in Cistanche tubulosa. The ACT molecules have high medicinal value, but the content of ACT is scarce. Therefore, it is imperative to develop the ACT-based molecularly imprinted composite membranes (A-MICMs) with highly selective separation of ACT. In this study, the amine-polyhedral oligomeric sesquisiloxanes (NH2-POSS) were uniformly introduced into polydopamine modified polyvinylidene fluoride (pDA@PVDF) membranes to fabricate NH2-POSS-pDA@PVDF. Then, the ACT-imprinted layers were synthesized on the surface of NH2-POSS-pDA@PVDF to obtain A-MICMs. The results showed that the optimal conditions were 180 mg DA, 12 h DA self-polymerization time, 400 mg NH2-POSS and 10 h washing time for the synthesis of A-MICMs. The results of adsorption isotherm experiments showed that there was a single layer adsorbate analyte on the A-MICMs. The results of adsorption kinetic experiments showed that chemisorption mechanism played a major function in the adsorption process of A-MICMs for ACT. The A-MICMs exhibited the maximum rebinding capacity of 98.37 mg⋅g−1, an excellent rebinding selectivity of 4.63, and the permselectivity of 7.02. The same A-MICMs kept 95.99% of the maximum rebinding capacity for ACT after 5 adsorption-desorption cycles. The designed A-MICMs with the interleaved imprinted network structure have a potential to be applied to the highly selective separation of bioactive components from natural products.

Removal of Fluoroquinolone Antibiotics by Chitosan–Magnetite from Aqueous: Single and Binary Adsorption

In this research, chitosan–magnetite composites (CS-MNPs) were successfully synthesized using a rapid and easy technique. The materials were characterized by FTIR, XRD, EDX, TEM, VSM, and BET methods. The removal of the antibiotics ciprofloxacin (CFX) and levofloxacin (LFX) from aqueous solutions by CS-MNPs adsorbent was investigated. The influencing factors in a single adsorption system were studied, including pH (1–11), initial concentration (2.5–15.0 mg/L), contact time (0–120 min), and adsorbent dosage (5–50 mg/L). The experiment data were analyzed by pseudo-first-order and pseudo-second-order kinetic models. The adsorption isotherms were studied by fitting the experimental data to the Langmuir, Freundlich, and Temkin models. The results indicated that the adsorption of CFX and LFX antibiotics was consistent with the pseudo-second-order kinetics model, the Langmuir isotherm model. Binary adsorption systems (CFX: LFX) with concentration ratios of 1:0, 1:0.5, 1:1.0, 1:1.5, and 1:2.0 were also studied. The antibiotics CFX and LFX were absorbed by CS-MNPs simultaneously in the aqueous solution. The presence of the second component in the solution reduced the first component’s ability to adsorb. The adsorption process in the binary system followed the Langmuir competition model. After four regenerations, CS-MNPS exhibited stability and was well reusable. Studies on actual samples showed that CS-MNPs could effectively remove FQs from those samples, with a treatment efficiency of above 98%.

Preparation of metal oxide-loaded nickel foam adsorbents modified by biochar for the removal of cationic dyes from wastewater

In this study, metal composite oxides grown on nickel foam were prepared, which were modified by dopamine and biochar to obtain cauliflower-shaped Co2MnO4/[email protected]/BC adsorption material to adsorb cationic dyes from aqueous solutions. The maximum adsorption amounts qmax for methylene blue (MB), malachite green (MG), and crystal violet (CV) were 8.44, 41.03 and 3.39 mg g−1, and the adsorption aligned with the Langmuir isothermal model as single molecular layer adsorption on a homogeneous surface. The adsorption experiments of dyes were conducted using lake water in the environment, and the adsorption rates of MB, MG, and CV were 91.4%, 94.8% and 85.1%, respectively. Meanwhile, the material has wide pH applicability (3–9), and good adsorption-desorption cycle performance. In addition, the synthesized adsorbent Co2MnO4/[email protected]/BC and the control adsorbent were investigated and shown to have good adsorption capacity. In conclusion, the adsorbent materials synthesized in this work have some application prospects in dye wastewater adsorption.

The effects of UiO-66 ultrafine particles on the rapid detection of sulfonamides in milk: Adsorption performance and mechanism.

Nanoscale MOFs particles possess both excellent adsorption and dispersion properties. In this study, ultrafine particles UiO-66 (UP/UiO-66) with a particle size below 50nm were synthesised by a template-controlled method. UP/UiO-66 was able to achieve a maximum adsorption capacity of 139.64mg/g for 5 methoxylated sulfonamides. Adsorption studies showed that UP/UiO-66 adsorption of sulfonamides can be classified as a pseudo-secondary kinetic adsorption model for single molecular layer adsorption. ELISA (validated by Raman and molecular docking) showed that the sulfonamide molecule was still immunoreactive with antibodies after adsorption by UP/UiO-66. In 15min, UP/UiO-66 could be used directly in the ELISA test for sulfonamides in milk without elution and separation. The LOQ (IC20) of UP/UiO-66-ELISA for sulfonamides in milk was 0.21-2.05ng/mL. The ultrafine particle strategy of UiO-66 is expected to be applied to other MOFs and used as a general pretreatment material for residue monitoring in complex matrices.

Cr-based metal–organic frameworks (MOFs) with high adsorption selectivity and recyclability for Au (Ⅲ): Adsorption behavior and mechanism study

Preparation of efficient adsorbents is of great significance for the recovery of precious metals from secondary resources. Herein, –NH2 was successfully grafted on MIL-101(Cr) via hydrothermal reaction to improve the adsorption capacity of Au (Ⅲ) in aqueous solution. MIL-101(Cr)–NH2 had a huge specific surface area (1016.50 m2‧g−1), which can provide more adsorption sites for Au (III). At 298 K, the maximum adsorption capacity of Au (III) by MIL-101(Cr)–NH2 was 792.43 mg∙g−1 and was higher than that by MIL-101(Cr) (140.83 mg∙g−1). The adsorption data was well fitted by Langmuir and pseudo-second-order models, confirming that the adsorption process conformed to single molecule adsorption and chemical adsorption. Mechanism study indicated that the adsorption of Au (III) by MIL-101(Cr)–NH2 was initiated with electrostatic attraction and promoted by reduction and inner complexation between AuCl4- and protonated amino groups. During adsorption, Au (Ⅲ) was reduced to Au (0) and Au (I) by –NH2. Density functional theory (DFT) calculation demonstrated that MIL101(Cr)–NH2 possessed higher binding affinity and more adsorption sites for Au (III) than MIL-101(Cr). Moreover, MIL-101(Cr)–NH2 exhibited excellent selectivity towards Au (III) and good recyclability, which is promising in the recovery of precious metals.

Designing novel perlite-Fe3O4@SiO2@8-HQ-5-SA as a promising magnetic nanoadsorbent for competitive adsorption of multicomponent VOCs

Volatile organic compounds (VOCs), which emerge as multicomponent pollutants through many industrial processes, pose a serious threat to human health and the eco-environment due to their volatility, toxicity and dispersion. Hence, the study of competitive adsorption of multicomponent VOCs is of practical and scientific importance. Herein, the perlite-supported Fe3O4@SiO2@8-hydroxyquinoline-5-sulfonic acid (perlite-Fe3O4@SiO2@8-HQ-5-SA) was designed as a novel magnetic nanoadsorbent by a simple strategy and employed for the competitive adsorption of multicomponent toluene, ethylbenzene and xylene in the vapor-phase targeted as VOCs. The successfully prepared perlite-Fe3O4@SiO2@8-HQ-5-SA was characterized by means of SEM, EDX, FT-IR, VSM and BET analyses. Adsorption capacities of 558 mg/g, 680 mg/g and 716 mg/g were achieved for single component toluene, ethylbenzene and xylene, respectively. It was concluded that the adsorption capacities for both binary and ternary components were significantly decreased compared to single component adsorption. The competitive adsorption capacity order of the binary and ternary component VOCs was xylene > ethylbenzene > toluene due to their competitive dominance. The rate-limiting kinetic analysis indicated that the adsorption rates were determined by both the film diffusion and intraparticle diffusion. The analysis of the error metrics demonstrated that the three-parameter isotherm models better described the adsorption data compared to the two-parameter models. In particular, the Toth model provided the closest fit to the experimental equilibrium data. The thermodynamic analysis indicated the spontaneous nature and probability (ΔG° <0), exothermic (ΔH° <0), physical (ΔH° <20 kJ/mol) and a declination in the degree of randomness (ΔS° <0) of the adsorption processes. The reuse efficiency of perlite-Fe3O4@SiO2@8-HQ-5-SA for toluene, ethylbenzene and xylene decreased to only by 88.91%, 88.07% and 87.16% after five recycles. The perlite-Fe3O4@SiO2@8-HQ-5-SA has a significant adsorptive potential compared to other adsorbents reported in the literature, thus it could be recommended as a promising nanoadsorbent for VOCs in industrial processes.