Composite Adsorbent Research Articles

Preparation and characterization of cauliflower-like γ-Fe2O3/H-γ-AlOOH magnetic composites with high adsorption performance towards As(V)

That long-term consumption of water with arsenic concentrations greater than 10 μg L−1 induces renal, hepatic, and cardiovascular diseases, in addition, the effective adsorbents for removing arsenic are limited by their harsh synthesis conditions, slow adsorption kinetics, low adsorption capacities and hard solid-liquid separation. Herein, a hierarchical cauliflower-like γ-Fe2O3/H-γ-AlOOH magnetic composites for the treatment of As(V)-contaminated wastewater is firstly proposed to avoid the complex centrifugation and filtration process, and achieve the purpose of simplifying operation. A series of physicochemical characterization tools reveal the successful synthesis of hierarchical cauliflower-like γ-Fe2O3/H-γ-AlOOH magnetic composite adsorbent with a large specific surface area (SBET) of 131.82 m2 g 1, high Zeta potential of +17.22 mV, and magnetic saturation (Ms) of 26.1 emu g−1, which synergistically improves the adsorption performance and achieve the purpose of simplifying operation. The related adsorption experimental data demonstrates that the saturated adsorption capacity for As(V) reaches 130.17 mg g−1 and decreases by only 17.6 % after six adsorption-desorption experiments, and the whole adsorption process conforms to Pseudo-second order model and the Langmuir model, which proves it is more inclined to be monolayer adsorption and there is no chemical reaction between As(V) and adsorbent. In addition, the adsorption of As(V) onto the cauliflower-like γ-Fe2O3/H-γ-AlOOH magnetic composites is assigned to a spontaneous, endothermic and entropy increased process. The main adsorption mechanism is that, combined with X-ray photoelectron spectroscopy (XPS) analysis, all components of the composite are involved in the adsorption of As(V), with the predominance of metal hydroxyl groups. The synthetic route of a novel and highly effective adsorbent, the hierarchical cauliflower-like γ-Fe2O3/H-γ-AlOOH magnetic composite material, provides a more promising alternative candidate for the As(V) treatment, from the perspective of aquatic ecosystem protection and solid-liquid separation.

Tailoring ethylenediamine functionalization on magnetic Zr-based metal-organic frameworks towards enhanced phosphate and tetracycline adsorption by synergy of Fe3O4 and amino functional groups

The development of efficient adsorbent for removing excessive nutrients (e.g. phosphorous – P) and antibiotics (e.g. tetracycline hydrochloride – TC) from livestock wastewater is necessary but challenging in practical application. In this study, magnetic Zr-based metal-organic frameworks (Fe3O4/UiO-66) with interfacial Fe-O-Zr bonds were synthesized and then modified with ethylenediamine (EDA) functional groups. The resultant optimized composite, namely Fe3O4/UiO-66-N2, showed promising removal of P and TC from both single and binary solution systems. It exhibited the maximum P and TC adsorption capacities of 90.0 mg P/g and 72.3 mg/g in the single component solution, respectively. In the binary solution with an initial P concentration of 5 mg P/L, the coexistence of TC posed a slight inhibition effect on the P adsorption over Fe3O4/UiO-66-N2. However, the TC adsorption was increased by raising the initial P concentration in solution from 5 mg P/L to 20 mg P/L. The Fe3O4 nanoparticles and EDA functional groups were suggested jointly improving the adsorption capacities of P and TC, with the synergy factors of 1.1 and 1.8, respectively. The effects of reaction time, water medium, initial pH and coexisting ions on the adsorption were investigated in detail. The mechanisms governing the adsorption of phosphate included electrostatic attraction, hydrogen bonding, ligand exchange and complexation. Those contributing to the adsorption of TC included Lewis acid-base interaction and π-π electron-donor-acceptor interaction, in addition to electrostatic attraction, hydrogen bonding and complexation. This work designed novel functionalized magnetic MOF composite adsorbents targeting at efficient and simultaneous removal of P and TC from water, under the synergistic effect of the Fe3O4 nanoparticles and surface functional groups.

Experimental Study on the Open Adsorption Performance of Water Vapor with DUT-67 and Its Composite Adsorbent

Experimental Study on the Open Adsorption Performance of Water Vapor with DUT-67 and Its Composite Adsorbent

Magnetically nanorized seaweed residue for the adsorption of methylene blue in aqueous solutions.

The cost-effective and green separation of dye pollutants from wastewater is of great importance in environmental remediation. Industrial seaweed residue (SR), as a low-cost cellulose source, was used to produce carboxylated nanorized-SR (NSR) via oxalic acid (OA)-water pretreatments followed by ultrasonic disintegration. Fourier transform infrared spectroscopy, X-ray polycrystalline diffraction, nitrogen isotherms, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, X-ray photoelectron spectrometry, particle charge detection, zeta potential and retro titration experiments were utilized to explore the physiochemical properties of samples. The NSRs with carboxyl content of 4.58-6.73 mmol g-1 were prepared using 10-60% OA-water pretreatment. In the case of 20% OA-water pretreatment, the highest NSR yield (73.9%) and nanocellulose content (80.2%) were obtained. Through self-assembly induced by the electrostatic interaction, magnetic NSR composite adsorbents (MNSRs) were prepared with the combination of NSR and Fe3O4 nanoparticles (NPs). The carboxylated NSR with negative charge demonstrated good affinity for Fe3O4 NPs. The Fe3O4 NPs were perfectly microencapsulated with the NSR when the NSR/Fe3O4 mass ratio was higher than 1/1. The adsorption properties of the MNSR for methylene blue (MB) removal from aqueous solution were investigated. The adsorbent with NSR/Fe3O4 mass ratio of 1/1 (MNSR1/1) exhibited optimum performance in terms of the magnetic properties and adsorption capacity. The MNSR1/1 showed high adsorption ability in a pH ≥7 environment. According to the Langmuir fitting, the maximum adsorption capacity of MNSR1/1 for MB reached 184.25 mg g-1. The adsorption of MB complies with the pseudo-second-order kinetic model. MNSR1/1 still maintained good adsorption properties after the fifth cycle of adsorption-desorption. MNSR1/1 could selectively adsorb cationic dye (i.e., MB and methyl violet) from wastewater, with hydrogen bonding and electrostatic interaction as the main force.

Investigations of Silica/MOF composite coating and its dehumidification performance on a desiccant-coated heat exchanger

Desiccant materials have an important impact on the dehumidification performance of desiccant-coated heat exchanger (DCHE). In this paper, a desiccant-coated heat exchanger based on a composite desiccant material of metal organic frameworks (MOFs) and silica gel was proposed. The coating was experimentally prepared and tested for its hygroscopic performance under different binder types (PVP, PVA, and PVB), different binder mass concentrations, and different MOF mass concentrations in the composite adsorbent. Further simulations were performed to investigate the effects of key structural and operational parameters on the performance of DCHE. Experimentally, the optimal hygroscopic performance of the composite adsorbent was obtained at 15 wt% PVP and 20 wt% MOF, which was 51.71 % higher than that of silica coating, and the cost of the composite adsorbent drops 78.04 % by comparing to the pure MOF for laboratory fabrication, and based on the novel economic efficiency index proposed in this paper, the mass concentration of the MOF should not exceed 32.8 wt%. Simulation results showed that under the conditions as follows: 1.2 mm (fin spacing), 25 mm (fin height), 0.28 mm (coating thickness), 25 °C (cooling water temperature), and 0 % (initial moisture content), the corresponding moisture removal capacity (MRC) and of DCHE was 6.740 g/kg, which was 149.63 % higher than that of silica coating.

Zearalenone removal using inactivated yeast embedded in porous modified yam starch aerogels and its application in corn silk tea

Zearalenone contaminates food and poses a threat to human health. It is vital to develop cost-effective and environmentally-friendly adsorbents for its removal. By screening Sporobolomyces pararoseus (SZ4) and modified yam starch (adsorption capacity (qe) of 1.33 and 0.94 mg/g, respectively), this study prepared a novel composite aerogel adsorbent (P-YSA@SZ410). The compressive strength of P-YSA@SZ410 was 1.35-fold higher than unloaded yeast. It contained several functional groups and three-dimensional interconnected channels, achieving a 0° contact angle within 0.18 s, thereby demonstrating excellent water-absorbent properties. With a qe of 2.96 mg/g at 308 K, the adsorption process of P-YSA@SZ410 was spontaneous, endothermic, and matched pseudo-second-order and Langmuir models. The composite adsorbed zearalenone via electrostatic attraction and hydrogen bonding, maintaining a qe of 2.24 mg/g after five cycles. P-YSA@SZ410 was found to remove zearalenone effectively under various conditions and could be applied to corn silk tea, indicating its great potential as an adsorbent material.

Composite flat-sheet membrane adsorbent of Li2TiO3-Ethylene-co-vinyl alcohol (LTO-EVAL) for lithium extraction

Composite bead adsorbents have been prevalent for the extraction of Li+ from brines. However, adsorbent beads generally demonstrate declining adsorption capacity and require extended equilibrium time when used repeatedly in absorption/desorption cycles. To overcome this challenge, a novel composite flat-sheet membrane adsorbent based on ethylene-co-vinyl alcohol (EVAL) and Li2TiO3 (LTO) is reported herein for highly efficient Li+ extraction from a geothermal brine. At an optimal LTO loading and membrane thickness, the resulting LTO-EVAL membrane was characterized by a large open macrovoid structure for fast ion transport, a fast adsorption rate that reached equilibrium in 0.5 h, and a high capacity of 96 % of that of the powder. The new membrane adsorbent showed adsorption behavior consistent with the Langmuir model and pseudo-second-order kinetic model. For a geothermal brine with a low lithium concentration, the LTO-EVAL membrane showed stable performance in 13 rapid adsorption/desorption cycles, with adsorption capacity at an average adsorption capacity of 7.3 mg/g and a 70 % adsorption efficiency. The average dissolution rate of Ti4+ was below 0.6 % in each cycle. The structure of the adsorbent material showed no discernable changes in chemical structure as confirmed by XRD and SEM results. With the improved extraction efficiency, the reusable membrane adsorbents would be economically viable in the long run and could potentially serve as the next generation of scalable Li+ adsorption material for brines. Further utilization of membrane adsorbent would lead to new design of adsorption modules and systems with reduced footprint. We need to further optimize the stability of the membrane adsorbents so that loss of Li2TiO3 remain at low level to reduce the lost for lithium extraction from the geothermal brine.

Molybdenum disulfide anchored peanut shell biochar composite for efficient adsorption of Pb2+: Performance and mechanism

Heavy metal lead (Pb2+) contamination in water poses a serious threat to human health, and developing some effective strategies for the removal of Pb2+ is urgent. Herein, molybdenum disulfide (MoS2) anchored peanut shell biochar (BC) composite adsorbents were successfully prepared by hydrothermal method and applied for the adsorption of Pb2+. Among these composites, the MoS2/BC-3 composite displayed the best adsorption performance with the adsorption capacity of 232 mg·g−1 at 30 °C. The adsorption procedure followed the pseudo-secondary kinetics and Freundlich adsorption model, indicating that the adsorption process of Pb2+ over MoS2/BC-3 composite was chemical and multilayer adsorption. Moreover, Pb2+ was spontaneously adsorbed by MoS2/BC-3, and the adsorption capacity increased with the enhance of temperature. The main mechanisms involved in the adsorption of Pb2+ by MoS2/BC-3 composite were found to include electrostatic interaction and complexation interaction. In addition, the MoS2/BC-3 composite had a good stability, and the Pb2+ removal rate could still reach more than 80 % after 6 cycles of adsorption experiments. Meanwhile, the adsorbent demonstrated a strong ability to absorb common heavy metals including copper and cadmium, further confirming that the MoS2/BC-3 composite had a potential value.

Sequential assembly enhanced selectivity on magnetic imprinted polymers for specific capture of naringin: A combination of synergistic dual sites and imprinted effect

Green and sustainable recovery of high-value natural flavonoids in agricultural wastes could not only improve natural resource utilization, but also could effectively reduce environmental pollution. Recently, great efforts have been made for research on the development of magnetic imprinted composite adsorbent, but the simultaneous promotion of stable selectivity and high adsorption amounts still faces its challenges. Inspired by “Sandwich-like” transport channels with proper steric and specific affinity sites, herein we designed a new kind of surface-imprinted magnetic colloidal nanocrystal clusters (MCNCs) with dual recognition sites (MCNCs@DR-MIPs) via sequential surface imprinted strategy. A two-step sequential surface-initiated atom transfer radical polymerization (SI-ATRP) was employed to construct the double imprinted sites, which can significantly improve the adsorption selectivity and adsorption amounts. In this design, the metal ion Zn(II) and the low pKa boronic acid APBA (1-allylpyridine-3-boronic acid, pKa = 7.4) could effectively tune the appropriate yolk-shell confinement sites, the obtained artificial double imprinted binding sites establishes the promising chemical environment for selective separation. As expected, the adsorption equilibrium experiments exhibited adsorption kinetics (180 min) and the maximum equilibrium binding capacity (34.60 µmol g−1). In virtue of unique advantages of magnetic separation materials, this novel absorbent exhibited a green and environmentally friendly enrichment process for naringin (NRG). Meanwhile, MCNCs@DR-MIPs showed excellent selectivity (imprinted factor 2.15) and regeneration properties (only decreased by 8.22 % after 7 cycles) for NRG. Additionally, the commercially available NRG could be effectively extracted and concentrated to 94.78 %. This study offers a sustainable effective strategy for flavonoids purification of magnetic separation materials and promotes advance the other natural compounds from agricultural wastes.

Carboxymethyl cellulose/activated carbon/hydroxyapatite composite adsorbent for remediation of methylene blue from water media

In the present study, activated carbon (AC), activated carbon/hydroxyapatite (AC/HAp), and carboxymethyl cellulose/activated carbon/hydroxyapatite (CMC/AC/HAp) composite adsorbents were prepared to remediation of methylene blue (MB) from water media. The pyrolysis method used the Pine cone as a natural precursor to synthesize AC. FTIR, XRD, Raman, BET, TEM, and SEM-Dot mapping techniques were applied to characterize synthesized adsorbents. Experimental results demonstrated that the maximum removal efficiency of AC, AC/HAp, and CMC/AC/HAp adsorbents under optimum conditions of pH 8, adsorbent dose 1 g/L, contact time 60 min, initial concentration 10 mg/L, and temperature 25 °C was computed to be 98.75, 98.86, and 98.93 %, respectively. Kinetic and equilibrium data were well-fitted with pseudo-second-order and Langmuir models, respectively. The maximum monolayer adsorption capacity of AC, AC/HAp, and CMC/AC/HAp was determined to be 40, 44.248, and 43.86 mg/g, respectively. FTIR results showed that hydrogen bonding and electrostatic interactions are the main mechanisms of the adsorption process. Results of the thermodynamic study showed that the adsorption process is spontaneous and exothermic. Finally, AC, AC/HAp, and CMC/AC/HAp composite adsorbents can be used as promising adsorbents for the remediation of MB from wastewater.

Thermodynamic study of zeolite and graphene nanoplatelet-based composites for adsorption cooling systems

The consolidated composite adsorbents containing AQSOA-Z02 zeolite and graphene nanoplatelets (GNPs), recently developed and exhibiting excellent thermophysical and water adsorption characteristics, are found to overcome the above-mentioned limiting factors. However, rigorous thermodynamic analysis has not yet been studied, which is crucial in the simulation of adsorption characteristics, system design, and ACS analysis. Therefore, this study aims to conduct a rigorous thermodynamic investigation and the assessment of performance parameters for various AQSOA-Z02 – GNPs–based composite/water pairs. In the thermodynamic analysis, the heat of adsorption (Qst) and the adsorbed phase-specific heat capacity (cp,a) are investigated theoretically. The study reveals that Qst decreases with adsorption uptake, while cp,a exhibits the opposite trend. The incorporation of H25-GNPs into zeolite leads to a reduction in both Qst and cp,a, contributing favorably to the design of an energy-efficient ACS. Additionally, the performance parameters such as specific cooling effect (SCE) and coefficient of performance (COP) are theoretically investigated with variations in desorption and evaporation temperatures. Both SCE and COP increase with evaporation and desorption temperatures. The composite containing 90 wt% AQSOA-Z02 and 10 wt% H25-GNPs exhibit the maximum COP value of 0.351 and the maximum volumetric cooling effect of 581.621 MJ m−3, which are almost 20% and 41% improvement over parent AQSOA-Z02 zeolite, respectively. All the findings of this study will greatly assist in the design of an energy-saving and eco-friendly adsorption cooling system.

Loofah sponge immobilized ZIF-8 for efficient adsorption removal of U (VI)

Efficient removal of radioactive and toxic uranium (U) from wastewater is highly desired. In this work, a novel adsorbent was prepared via in situ introducing zeolitic imidazolate framework-8 (ZIF-8) onto the hydrolyzed biomass loofah sponge (HLS) for the removal of U (VI). Benefiting from the introduction of ZIF-8, the physical and chemical properties of the composite adsorbent were significantly improved, leading to an enhanced U (VI) adsorption capacity. The results show that the maximum adsorption capacity of the adsorbent toward U (VI) is 244.03 mg/g under the optimal conditions. The adsorption kinetic parameters and isotherm of U (VI) well follow the pseudo second order model and Langmuir model, respectively. Besides, the thermodynamic parameters shows that the adsorption process of U (VI) is a spontaneous process with an exothermic nature. More importantly, the prepared adsorbent has a good reuseability and anti-interference capability during the adsorption of U (VI). This work supplies a new routine to design highly performed adsorbents for the removal of U (VI).

Adsorptive removal of uranium(VI) from aqueous solutions by amino-functionalized montmorillonite@β-cyclodextrin composite

For economic and environmental security consideration, an amino-functionalized montmorillonite@β-cyclodextrin composite adsorbent (NH2-MMT@β-CD) was successfully synthesized to adsorb uranium(VI). NH2-MMT@β-CD performed excellent uranium(VI) removal performances with the uranium(VI) removal capacity of 469.4 mg/g, which was almost three times that of MMT. The reason for the improvement was that the introduction of 3-aminopropyltriethoxysilane and β-CD not only enhanced the d-spacing and surface roughness, but also brought abundant functional groups, like amino and hydroxyl groups, thus providing more useable active sites. Besides, NH2-MMT@β-CD also had good selectivity and favorable stability with the uranium(VI) removal efficiency of 90.4 % at the fifth cycle. Characterizations indicated that NH2-MMT@β-CD adsorbed uranium(VI) via electrostatic interaction, complexation, reduction reaction and ion-exchange. This work supplied a new idea for exploring novel clay-based adsorbents for selective and efficient removal and regeneration of uranium(VI) from aqueous solution.

Conjugated polymers decorated lignocellulosic nanocomposites for malachite green contaminated water remediation

Various novel conjugated polymer composites were synthesized via in situ chemical oxidative polymerization on lignocellulosic waste, notably Azadirachta indica sawdust. The composites, including Azadirachta indica/polyindole (AIS/PIn), Azadirachta indica/polyaniline (AIS/PAn), Azadirachta indica/polythiophene (AIS/PTh), and Azadirachta indica/polypyrrole (AIS/PPy), were investigated for their porous structure, ease of synthesis, unique adsorptive properties, and adjustable morphology. The synthesized composites were characterized using SEM/EDS, TEM/SAED, XRD, BET, TGA, and FTIR, revealing detailed insights into their structural and morphological features. The potential of these composites as efficient adsorbents for removing malachite green (MG) dye from water was a vital focus of this research. Batch experiments were conducted to assess the impact of various factors on adsorption, such as adsorbent/adsorbate contact time (0–280 min.), adsorbent dosage (0.4–20.0 g/L), initial adsorbate concentration (25–100 ppm), pH (2–13), and temperature (30–60 °C). The results indicate a remarkable removal efficiency of 89.98 % for MG with an initial concentration (Co) of 50 mg/L, achieved within 120 min using 0.4 g/L of AIS/PIn at a pH above 8.3. The Langmuir adsorption isotherm model provided the best fit for the experimental data, with maximum adsorption capacities of 384.61 mg g−1 for AIS/PIn, 344.82 mg g−1 for AIS/PAn, 277.77 mg g−1 for AIS/PTh, and 256.41 mg g−1 for AIS/PPy. This suggests monolayer adsorption. The adsorption kinetics conformed to a pseudo-second-order model, with the process being endothermic, feasible, and associated with positive entropy, thereby underlining its favorability and spontaneity. The desorption studies determined that 0.1 M HCl was the most effective desorbing agent compared to NaOH, NaCl, CH3COOH, and H2O. The spectral and effect of pH analyses suggested that the adsorption mechanisms might involve multiple interactions, prominently including electrostatic interactions, hydrogen bonding, π-π interactions, and n-π interactions. Based on the findings, it is submitted that the conjugated polymer decorated biomass composite adsorbents exhibit reasonable recyclability over multiple cycles, versatility, and potent efficacy as low-cost adsorbents for eliminating MG dye from aqueous systems.

Synergistic adsorption of methylene blue using ternary composite of phosphoric acid geopolymer, calcium alginate, and sodium lauryl sulfate.

The removal of dyes from the aquatic ecosystem is necessary being a major threat to life. For enhanced remediation of methylene blue (MB) dye, a new ternary biopolymer-geopolymer-surfactant composite adsorbent is synthesized by combining phosphoric acid geopolymer (PAGP), calcium alginate (Alg), and sodium lauryl sulfate (SLS). During the synthesis of the composites, PAGP and SLS were mixed with the alginate matrix, producing porous hybrid beads. The PAGP-SLS-alginate (PSA) beads prepared were characterized using different analytical tools, i.e., scanning electron microscopy (SEM), Fourier transform infrared spectrophotometry (FTIR), X-ray diffractometry (XRD), surface area and porosimetery (SAP), and thermogravimetric analysis (TGA). To ascertain the ideal conditions for the adsorption process, a batch reactor procedure was used to investigate the effects of several parameters on MB adsorption, including pH (2, 4, 6, 8, 10), PSA adsorbent dosage (0.06-0.12 g), MB concentration (50-500 mg/L), contact time (15 to 300 min), and temperature (25, 35, and 45 °C). The SEM investigation indicated that ~ 1860 μm-sized PSA beads with 6-8 μm voids are generated. Based on XRD, FTIR, and SAP examinations, the material is amorphous, having numerous functional groups and an average pore size of 6.42 nm. Variation of pH has a little effect on the adsorption process, and the pH of 7.44 was found to be the pHpzc of the PSA beads. According to the findings of the batch study, equilibrium adsorption was obtained in 270-300 min, showing that the adsorption process was moderately slow-moving and effective. The dye adsorption linearly increased with initial dye concentration over concentration range of 50-500 mg/L and reciprocally decreased with rise in temperature. 0.06 g adsorbent dose, 25 °C, pH10, and 270 min were found to be the better conditions for adsorption experiments. Langmuir isotherm fitted well compared to Freundlich, Temkin, and Dubinin-Radushkevich (DR) isotherm models on the experimental data, and the maximum adsorption capacity(qmax) calculated was 1666.6 mg. g-1. Pseudo-second-order (PSO) kinetics model and multi steps (two) intra particle diffusion (IPD) model fitted well on the adsorption kinetics data. The system's entropy, Gibbs free energy, and change in enthalpy were measured and found to be -109.171 J. mol-1. K-1, - 8.198 to - 6.014 kJ. mol-1, and - 40.747 kJ. mol-1. Thermodynamics study revealed that adsorption process is exothermic, energetically favorable and resulting in the decrease in randomness. Chemisorption is found to be the dominant mechanism as confirmed by pH effect, Langmuir isotherm, PSO kinetics, IPD model, and thermodynamics parameters. PSA beads were successfully regenerated using ethanol in a course of 120 min and re-used for five times. To sum up, the PSA adsorbent's impressive adsorption capability of 1666.66 mg/g highlights its potential as a successful solution for methylene blue removal. The results of this study add to the expanding corpus of information on sophisticated adsorption materials and demonstrate PSA's potential for real-world uses in wastewater treatment and environmental clean-up.

Lanthanum-Integrated Porous Adsorbent for Effective Phosphorus Removal.

In pursuit of accessing clean water, the phosphate removal is of great importance for preventing eutrophication toward sustainable ecology. However, effective adsorbents with high capacity, selectivity, and long-term stability for treating phosphate in water still remain desired, which requires further development. Herein, a type of porous La-based adsorbents, which are composed of highly dispersed La(OH)3 on amino-functionalized Caragana korshinskii (CK) nanowires, are designed and fabricated through simple amination and decoration of lemon bars. Specifically, the adsorption to phosphate can be quickly completed within 50 min, and an ultrahigh adsorption capacity of 173.3 mg of P g-1 is realized. Moreover, these composite adsorbents display excellent selectivity and anti-interference ability to phosphate in the presence of common anions (CO3 2-, NO3-, Cl-, and SO4 2-). After four regenerations, there is still a removal rate of 85%. This study underscores an integrated material model for designing advanced structures toward efficient wastewater treatment.

Hydrogen sulphide removal from raw biogas using novel coconut husk and sugarcane bagasse composite biochar adsorbent

Abstract The presence of water, hydrogen sulfide (H2S), ammonia, oxygen, nitrogen, and siloxanes in biogas is not desirable for thermal and electrical applications through the engine route. H2S adversely affects engines and fuel cells by causing corrosion on metal components, poisoning catalytic converters, and accelerating wear and tear, compromising performance and longevity. To meet specific quality requirements for diverse applications such as heating, combined heat and power generation, vehicle fuel, and fuel cells, biogas must undergo cleaning and upgrading processes. Using biochar to remove H2S in biogas is a comparatively new technique and can be a promising option for small-scale, decentralized units. Current research primarily investigates the potential of biochar derived from coconut husk (CH) and sugarcane bagasse (SB) for effectively removing H2S from raw biogas within an experimental framework. The selection of a composite material consisting of equal parts CH and SB was based on available literature and material accessibility. The integrated methodology provided comprehensive insights into the performance of biochars in biogas purification. Morphological analysis elucidated the role of pore structure in facilitating H2S removal, while CHNS analysis highlighted the influence of elemental composition on biochar reactivity. Additionally, pH studies underscored the potential for biochar application to mitigate biogas acidity. According to the findings, the biochar from the combination of CH and SB exhibited a removal efficiency of 77.60% for H2S in raw biogas.

Adsorption performance and mechanism of pectin modified with β-cyclodextrin for Zn2+ and Cu2+

Removing heavy metals from aqueous solutions has drawn more and more attentions these years because of their serious global health challenge to human society. To develop an adsorbent with green, stable and high-efficiency for adsorption of heavy metals, pectin β-cyclodextrin composite was successfully prepared and used for Zn2+ and Cu2+ adsorption for the first time. Various variables that influence the adsorption performance were explored, and the optimal adsorption conditions were determined. According to the pseudo-second-order kinetic model, the adsorption process of Zn2+ and Cu2+ by the adsorbent was mainly chemical adsorption. The adsorbent adsorption process was an exothermic and non-spontaneous process. According to the Langmuir isotherm model, the maximum adsorption capacity was 12.51 ± 0.33 and 24.98 ± 0.23 mg/g for Zn2+ and Cu2+, respectively. The FTIR, EDX and XPS results revealed that the main mechanisms of removing pollutants by adsorbent were ion exchange and coordination. In addition, electrostatic attraction and chelation were present in the adsorption process. After five adsorption desorption cycles, the pectin β-cyclodextrin composite adsorbent still exhibited adsorption and regeneration capabilities. This study provides a low-cost, effective and simple method for preparation of modified pectin, which has excellent application potential in the removal of heavy metal ions from wastewater.

Zeolitic imidazolate framework-8/layered triple hydr(oxide) composite for boosting the adsorptive removal of acid red 1 dye from wastewater

Water pollution is one of the serious environmental problems the humanity currently faces. Adsorption is an attractive process for tackling water pollution. Accordingly, novel adsorbents were synthesized in this study through the coupling of zeolitic imidazolate framework-8 (ZIF-8) with MnCuAl layered triple hydroxide/oxide (MnCuAl-LTH/MnCuAl-LTO) via different approaches. The synthesized adsorbents were characterized using different techniques in order to reveal their textural properties, crystallinity, and functional groups before applying them to decontaminate wastewater samples contaminated with acid red 1 (AR1) azo dye. The BET results revealed that all the synthesized materials are highly porous with specific surface area ranging from about 35 to more than 1200 m2/g. Additionally, the XRD and FTIR results confirmed the formation of the targeted pristine and composite adsorbents. Preliminary adsorption studies showed that the ZIF-8@MnCuAl-LTH composite is the most effective material in removing AR1 from wastewater. Potential mechanism(s) for the superiority of ZIF-8@MnCuAl-LTH over other adsorbents (i.e., MnCuAl-LTH@ZIF-8, MnCuAl-LTO@ZIF-8, MnCuAl-LTH, MnCuAl-LTO, and ZIF-8) has been discussed. The results also demonstrated that the adsorption of AR1 onto ZIF-8@ MnCuAl-LTH is strongly pH-dependent. The adsorption isotherm results confirmed that the removal of AR1 is best fitted by the Redlich-Paterson isotherm with a high degree of compatibility with the Langmuir isotherm model. Similarly, the experimental data were well-fitted to the Avrami model, confirming the complex nature of AR1 adsorption onto ZIF-8@ MnCuAl-LTH. Additionally, the regenerability and stability of this adsorbent have been investigated, and the obtained results revealed that this adsorbent is stable and has a good reusability. Accordingly, the ease of fabrication, high adsorption capacity (qmax is about 1000 mg/g), and the good stability and reusability make ZIF-8@MnCuAl-LTH a very promising adsorbent for removing anionic azo dyes from wastewaters, demonstrating the significance of this study.

Selective adsorption of cationic dyes by layered double hydroxide with assist algae (Spirulina platensis) to enrich functional groups

The present study involved the preparation, characterization, and evaluation of layered double hydroxide (LDH) with the assistance of the algae Spirulina platensis (NiAl-Sp and ZnAl-Sp). These materials were investigated for their potential for selective adsorption of cationic dyes, including rhodamine B, malachite green, and methylene blue. The adsorbents exhibit a significant level of selectivity in their capacity to adsorb malachite green in comparison to other cationic dyes. The next parameter of adsorption was evaluated in malachite green as the selective adsorption of cationic dyes. Based on the Langmuir isotherm model, the calculated maximum adsorption capacities of NiAl-Sp and ZnAl-Sp for malachite green were determined to be 478.190 mg/g (pH = 4, 50 °C for 30 min) and 123.457 mg/g (pH = 4, 30 °C for 30 min), respectively. The main processes of adsorption encompassed not only electrostatic interactions but also hydrogen bonding and π-π interactions involving the dye and the amino, hydroxyl, and carboxyl functional groups derived from Spirulina platensis. Spirulina platensis enhances the functional group of LDH. The findings of this study indicate that the NiAl-Sp and ZnAl-Sp composite demonstrated stability as a sorbent for the adsorption of malachite green. Furthermore, it was observed that this composite could be utilized for up to four adsorption cycles, but there was a noticeable decrease in its adsorption capability over time. The findings revealed that the synthesized composite adsorbents of NiAl-Sp and ZnAl-Sp exhibit high efficacy in the adsorption of malachite green from effluent.