Adsorbent Material Research Articles

Recent development on neem (azadirachta indica) biomass absorbent: surface modifications and its applications in water remediation

This review paper discusses the latest advances in transfiguring Azadirachta indica (neem) biomass into an adsorbent and how it can be used to clean the environment. As an economical and environmentally favorable adsorbent material, neem biomass has become increasingly popular due to its bioactive properties and abundance. The review breaks down modification techniques into chemical and physical processes. Important physical changes covered include preactivation, carbonization, and using fluidized bed technologies and rotary kilns. It has been shown that these methods greatly improve the surface properties of neem biomass, which makes it better at absorbing things and holding more. The changes that were made also have an effect on the adsorption kinetics and isotherms, which helps us understand the adsorption rates and equilibrium behaviors of the changed adsorbents better. Neem biomass adsorbents are illustrated through their versatility and efficacy in the removal of organic pollutants, dyes, and heavy metals from effluent. This is illustrated through specific applications. Additionally, computational studies and artificial intelligence are looked into to see if they can help us understand how adsorption works at the molecular level, improve the efficiency of modification processes, and guess how adsorption will behave. The review also talks about the research gaps and suggests areas for future research. The review emphasizes the crucial importance of integrating experimental and computational methods to enhance the performance of the modified neem biomass and increase its environmental cleaning potential.

Mixed Matrix PVDF Microfiltration Membranes with In-situ Synthesized Polyethyleneimine Particles as a Platform for Flow Through, High Capacity, Weak Base and Salt Tolerant Anion Exchange Membrane Adsorbers for Downstream Bioprocessing

The rapid growth of the monoclonal antibody (mAb) therapeutic market has led to a need for improved downstream bioprocessing, including mAb capture and release from bioreactor harvests followed by product purification and polishing. Membrane chromatography (MC) is poised to displace resin-based column chromatography in mAb product polishing. To remove negatively charged product impurities (e.g., host cell proteins, DNA, viruses, and endotoxins), anion exchange (AEX) membrane adsorbers offer higher process rates and eliminate the risks of cross contamination as they can be deployed as single use separation devices, which are increasingly being utilized in downstream bioprocessing to increase manufacturing speed and decrease production cost. Here, we describe a one-pot and single step phase inversion casting process for the preparation of a family of mixed matrix polyvinylidene fluoride (PVDF) microfiltration (MF) membranes with in-situ synthesized polyethyleneimine (PEI) microparticles that can serve as flow through, high capacity, and salt tolerant weak base AEX membrane adsorbers. These new membranes have a high content of weak base (WB) groups (primary and secondary amines) by virtue of the utilization of bis(2-chloroethyl)amine hydrochloride (BCAH) as crosslinker in the in-situ synthesis of PEI microparticles in the dope dispersions prior to membrane casting. By varying the concentration of PEI and BCAH in the casting dispersions, we successfully utilized nonsolvent induced phase separation (NIPS) with isopropyl alcohol as the nonsolvent in the membrane coagulation bath to prepare a mixed matrix PVDF-PEI MF membrane with (i) a relatively uniform and open microstructure in which the PEI particles completely cover the PVDF spherulites present at the membrane surface and cross section, (ii) high water flux (>1000 liters/m2/hr. at 2 bar) and (iii) a high loading of BCAH crosslinked PEI microparticles (51.0 wt.%) containing weak base primary, secondary, and tertiary amine groups. The protein binding measurements show that this new mixed matrix PVDF-PEI MF membrane can serve as a flow through, high capacity, and salt tolerant WB AEX membrane adsorber with a bovine serum albumin (BSA) dynamic binding capacity of ∼60 mg BSA per mL of membrane in a 50 mM TRIS buffer containing 100 mM of NaCl (15 mS/cm) at 10% breakthrough and flow rate of 10 MV/min. The overall results of this study indicate that our mixed matrix PVDF-PEI MF membranes with in-situ synthesized and BCAH crosslinked PEI microparticles have a promising potential to serve as a platform for the design, preparation, and scale up of a new generation of flow through, high capacity, salt tolerant, WB AEX membrane adsorber materials for downstream bioprocessing.

New Schiff base covalently bonded Graphene Oxide for removing Chromium(VI) from Surface Runoff.

Hexavalent chromium (Cr(VI)) poses severe health and environmental risk, especially in industrial vicinities where runoff concentrations are elevated by evaporation and sedimentation dynamics. This study investigates the utilization of modified graphene oxide (GO) with abundant active groups as an adsorbent. The novel adsorbent, GO/ATA, was synthesized by covalently attaching a Schiff base (ATA) to GO via a coupling reaction, enhancing its adsorptive properties. The physicochemical properties of GO/ATA were meticulously characterized to ascertain structural and morphological attributes. GO/ATA exhibit exceptional adsorptive capabilities, surpassing the performance parameters of other adsorbents with a maximum of 243.3 mg g-1 at 298 K. The electrostatic attraction between the N-containing functional groups in the graphene oxide and Schiff base composite (GO/ATA) and Cr(VI) is the main mechanism behind the adsorption process; Subsequently, a reduction reaction occurs, facilitated by the thiol and N-containing functional groups in GO/ATA composite, resulting in the transformation of Cr(VI) into Cr(III). This transformation is essential for the following chelation process occurring on the surface of the adsorbent material. Evaluations of recyclability indicated that GO/ATA retains substantial adsorption efficacy, with a reduction from 91.2% to 72.7% over five cycles, thus affirming its recyclability and practical application in the remediation of Cr(VI)-contaminated waterborne environment. Additionally, GO/ATA's effectiveness in removing Cr(VI) from surface runoff was specifically tested, emphasizing its economic and environmental viability.

Amino acid functionalized carboxymethyl cellulose-based crosslinked aerogels for efficient removal of dye and metal ion from aqueous solution

In order to protect water resources and maintain sustainable development of society, it is crucial to design the adsorption materials with high adsorption capacity and environmental friendliness to effectively remove the pollutants in wastewater. In this study, amino acid functionalized carboxymethyl cellulose-based aerogels were successfully prepared by combining grafting, blending, freeze-drying and crosslinking technologies. The aerogels exhibited outstanding adsorption properties for methylene blue (MB) and lead ions (Pb (II)) with adsorption capacities of 461.68 and 304.60 mg/g, respectively. The adsorption experiment showed that the adsorption process of aerogels for MB conformed to Freundlich adsorption isotherm model and quasi-second-order kinetics model, and the adsorption process for Pb (II) conformed to Langmuir model and quasi-second-order kinetics model. Furthermore, the aerogels displayed excellent recyclability, with the removal efficiency of over 90.0 % for MB and only 14.0 % reduction for Pb (II) after 6 cycles. It is evident that the aerogels hold great potential for application in wastewater treatment, which has important practical significance for environmental protection and high-value utilization of natural polymers.

PVA-enhanced green synthesis of CMC-based lithium adsorption films

The titanium-based lithium ion sieve (HTO), renowned for its exceptional adsorption performance and cyclic stability, was utilized in addressing the global shortage of lithium resources. However, the recovery and reuse efficiency of HTO in powder form is relatively low, which limits its application in industrial fields. To address this issue, this study utilized carboxymethyl cellulose (CMC) as the principal matrix material, while polyvinyl alcohol (PVA) played a dual function as both matrix and crosslinker, negating the necessity for supplementary crosslinking materials. Employing water as the only solvent, HTO was embedded into the CMC-PVA blended film matrix. It was observed that augmenting the CMC content substantially elevates the adsorptive capability of the film. However, this enhancement comes at the cost of reduced mechanical robustness and diminished stability in solution. Consequently, by balancing the influence of adsorptive capacity and stability through fine-tuning the CMC-to-PVA ratio. Even when HTO powder is encapsulated within the film, the adsorption film retains the excellent adsorption properties of HTO, achieving an adsorption capacity for lithium of 29.21 mg g−1 within 12 h. This study provides an innovative pathway and ideas for the large-scale, low-cost production of sustainable lithium-ion adsorption materials.

Preparation of Calcium-based Phosphate Adsorbent and Mineral-rich Humic acid Fertilizer from Biomass ash and Bamboo by Hydrothermal-pyrolysis: Performance and Mechanism

Biomass ash (BA) contains alkaline cations such as K, Ca, and Mg. Due to its high pH, direct application to the soil may result in soil salinization. Composting of BA with organic matter is an effective strategy, but the composting cycle is long and there is a large amount of insoluble residue in the product. Therefore, this research proposed for the first time using the hydrothermal method to rapidly convert BA and bamboo powder (BP) into water - soluble fertilizer (WSF) within 2 hours. The insoluble hydrothermal residue was further converted into calcium - rich biochar phosphorus adsorption material by a simple pyrolysis process. WSF was neutral and contained humic acid and elements like K, Ca, Mg, and Si. A 14 - day wheat hydroponic experiment showed that the addition of 0.0125% WSF increased the fresh weight of wheat by 18.77% compared with deionized water. The calcium - based biochar adsorbent produced by pyrolysis had an ideal adsorption capacity of up to 113.6mg P g-1 for phosphate in water, higher than many existing reports. The adsorption mechanisms mainly included surface precipitation, ion exchange, and electrostatic attraction. Moreover, the calcium - rich biochar sample slowly released phosphorus into water after adsorbing phosphate. When the pH was 3 or 4, the removal rate of Pb2+, Cd2+, and Cu2+ at 15 - 20 mg L-1 was as high as 99%. This indicated its potential as a slow - release fertilizer and heavy metal remediation agent. This research provided a new way of thinking for the treatment and disposal of BA.

Preparation and Characterization of Materials for Low- to Intermediate-Temperature CO2 Adsorption

Global carbon dioxide emissions are rising and the use of fossil fuels in several sectors are the leading causes. As global population and economies continue to grow significantly, the most practical method of lowering such emissions is to capture CO2. Although other technologies are more developed, adsorption is very promising and has attracted much attention. To ensure this technology’s success, it is essential to have suitable CO2 adsorbent materials. In this work, several new hydrotalcites (HTs) with different initial concentrations of ion precursors were prepared for the first time by the co-precipitation method—it was possible to verify that the ion concentrations influence the characteristics of the materials. The prepared HTs were characterized by thermogravimetric analysis (TG), X-Ray diffraction (XRD), surface area measurements and temperature-programmed desorption of CO2 (TPD-CO2) to relate their CO2 capture capacity to their physicochemical properties; the CO2 adsorption equilibrium isotherms were determined at 35 and 300 °C for the prepared samples, as well as for some commercial materials: magnesium oxide, calcium oxide, aluminium oxide and Zeolite 13X. After determining which materials present the best CO2 adsorption capacity, these were submitted to adsorption-desorption cycles to study their stability. The main objective of the work was to prepare and study different CO2 adsorbents for processes that are carried out at low and intermediate temperatures. From the experimental results, it was possible to conclude that the Zeolite 13X showed the best capacity at 35 °C, 3.38 mmol·g−1 (@ pCO2 = 1 bar), and a prepared calcined HT (c-HT2) was the best at 300 °C, 0.97 mmol·g−1 (@ pCO2 = 1 bar). Moreover, it seems there is an optimum initial concentration of the ions’ solutions for the tested HTs, which depends on the final application—c-HT1 showed a better capacity at 35 °C and c-HT2 at 300 °C. From the adsorption-desorption cycles—performed at 35 and 300 °C with the best materials using a magnetic suspension microbalance at 1 bar of CO2 partial pressure —, a working cyclic capacity of 2.69 mmol∙g−1 was achieved by the Zeolite at 35 °C; in turn, c-HT2 showed a working cyclic capacity of 0.79 mmol∙g−1 at 300 °C.

Two Sustainable Pathways of MOF-Catalyzed Room Temperature Chemical Fixation of CO2 inside Alkynes under Atmospheric Pressure.

The rising atmospheric CO2 levels necessitate the development of effective materials for its mitigation. Utilization of adsorbent materials for the reversible physisorption of CO2 has a significantly less impact. Recognizing this need, herein, we present a nitrogen-rich, aqua-stable, Ag(0)-nanoparticle-doped metal-organic framework (MOF) designed for the irreversible chemical conversion of CO2 into valuable fine chemicals. We demonstrate two sustainable pathways for CO2 fixation, utilizing the catalyst, 1'@Ag NPs. The designed catalyst facilitates the cyclization of propargylic amines and alcohols under ambient temperature and pressure conditions. Remarkably, this is the first MOF-based catalyst that allows for quantitative conversion of propargylic amines into 2-oxazolidinones at room temperature with atmospheric CO2 pressure. The process successfully transforms various propargylic amines and alcohols into 2-oxazolidinones and α-alkylidene cyclic carbonates under the CO2 atmosphere. Additionally, the catalyst shows excellent recyclability, maintaining its activity and structural integrity across multiple reuse cycles. Control experiments revealed that the catalytic efficiency of 1'@Ag NPs is attributed to the highly exposed alkynophilic Ag(0) sites on its pore walls. Computational studies further elucidate the mechanistic pathway for CO2 fixation. This work highlights the potential of 1'@Ag NPs to enhance environmental sustainability by converting CO2 into valuable bioactive chemicals under mild conditions.

Sulfadimethylpyrimidine degradation by non-radical dominated peroxomonosulfate activated with geopolymer-loaded cobalt catalysts

Geopolymers are frequently employed as adsorbent materials to treat heavy metals in wastewater due to their special structure analogous to that of zeolites. Nevertheless, their utilization as catalyst supports has not been extensively employed. In this study, geopolymers were modified using carboxymethyl chitosan and subsequently converted into zeolite through the hydrothermal method. Following calcination with Co loading, Co@MGA was obtained. The results indicated that as-prepared Co@MGA exhibited an excellent performance in activating PMS to degrade SMT. Moreover, the mineralization rate of SMT reached 76 %. Quenching experiments and electron paramagnetic resonance analyses had demonstrated that the non-radical pathway predominated in the degradation process of SMT, and 1O2 was the primary reactive oxygen species. The formation of surface bond was further elucidated through in-situ Raman spectroscopy and electrochemical tests. The potential mechanism and pathways of SMT degradation within the Co@MGA/PMS system were proposed. The system exhibited adaptability to different pH levels and robust resistance to inorganic ions and humic acid. Co@MGA demonstrated excellent reusability and stability, suggesting that Co@MGA is a highly promising catalyst for the activation of PMS.

Waste refractory brick material added chitosan/oxidized pullulan complex gel production and removal of heavy metals from waste water

Wastewater is a by-product of numerous industrial processes that have been demonstrated to have adverse effects on human and natural health due to the pollutants it contains. The pollutants in these substances are organic or inorganic molecules and heavy metal ions that significantly harm the environment and human health. A variety of techniques have been devised for the removal of heavy metal ions from wastewater. The adsorption process has attracted significant attention due to its straightforward implementation, cost-effectiveness, and the environmentally friendly production of adsorbent materials using biocompatible substances. In this study, the removal of Cu2+ ions from wastewater was conducted using chitosan pullulan, a biocompatible and biodegradable polymer. In addition to chitosan and pullulan, waste refractory materials from a furnace used in iron and steel production were added to these polymer materials to increase the adsorption capacity. The initial step involved grinding the waste refractory brick material. Subsequently, chitosan was dissolved in acetic acid. After that, the refractory material was suspended in this solution, facilitating the formation of hydrogel beads using a NaOH solution. The obtained hydrogels were coated with pullulan to produce polyelectrolyte gel. Pullulan was oxidized to 6-carboxypullulan by the TEMPO (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl) oxidation method and the negatively charged groups in its structure interacted with the positively charged groups in the chitosan structure to produce a complex gel. The chemical structure, morphological analysis, thermal analysis, and water release analysis of the produced waste refractory brick material added chitosan/oxidized pullulan complex gels were examined. The impact of the 6-carboxypullulan coating on the gels’ properties was elucidated. Furthermore, the adsorption of Cu2⁺ was conducted using solutions containing 100, 500, and 1000 ppm Cu2⁺ ions. It has been observed that the material can clean water with over 98% efficiency, even in solutions that exceed the standards set for wastewater. The material’s efficacy in cleaning solutions with concentrations above the standard for wastewater cleaning is evidence of its high performance. Furthermore, the kinetics and isotherm of the adsorption reaction were examined. The kinetics were determined to be consistent with the Pseudo Second Order (chemical reaction controlled) and aligned with the Langmuir and Freundlich Isotherm (mixed adsorption occurred on homogeneous and heterogeneous surfaces).

Adsorption characteristics and mechanism of novel ink melanin composite modified chitosan for Cd(II) in water

In this study, chitosan (CS), carboxymethyl chitosan (CMCS), and chitosan quaternary ammonium salt (HACC) were successfully loaded with ink melanin (ME) as efficient adsorbents for Cd(II) removal. The results of batch adsorption experiments and structural characterization showed that the modified CS loaded with ME improved the adsorption capacity of the composites for Cd(II). The pseudo-second-order kinetic and Langmuir equations were better suited to describe the batch adsorption experiments. The adsorption of Cd(II) was chemisorption with desirable adsorption effect when the concentration of the three composites was 0.5 mg/mL and the pH value was neutral. Among them, HACC-ME demonstrated remarkable Cd(II) adsorption performance (107.18 mg/g) and sustained an 85 % efficiency in Cd(II) removal over five adsorption-desorption cycles. Ion exchange, complexation, electrostatic attraction, and hydrophobic interaction were the primary mechanisms for Cd(II) removal. Overall, HACC-ME could be employed as a low-cost and highly efficient new natural adsorbent material for the removal of Cd(II) ions from wastewater. These findings illuminate pathways for the development of efficient and novel natural adsorbent materials for environmental cleanup purposes.

Controlled fabrication of hierarchical porous carbon nanospheres with high doped nitrogen content for high-performance adsorbent of biomacromolecule

Constructing nitrogen-doped porous carbons with high specific surface area, rapid mass transfer channels, and positive charge is a crucial requirement for high-performance adsorbents. Herein, by the kinetic self-assembly synthesis strategy, we prepared nitrogen-doped hierarchical porous carbon spheres (N-HPCS) with adjustable pore structure, high specific surface area, and high nitrogen doping content (8.88 %). By using ethylenediamine as an assisted polymerization and assembly agent, the hydrolysis and condensation rate of tetraethyl orthosilicate (TEOS) as the silica source and the condensation rate of 3-aminophenol and formaldehyde as the phenolic resin precursor were controlled by adjusting ammonia volume as the alkaline catalyst to tune kinetic self-assembly of silica and phenolic resin components, thus achieving their simultaneous or sequential nucleus and growth. After carbonization and selective silica etching, three types of carbon nanospheres with center-radial pores, hollow center-radial pores and hollow structure were obtained. High nitrogen doping content endowed the nanospheres with positive charge. Through adsorption experiments on the bovine serum albumin (BSA) and Hemoglobin (Hb) as typical biological macromolecules, hollow carbon nanospheres with center-radial pores exhibited excellent adsorption performance for BSA(622.34 mg g−1) and Hb(759.96 mg g−1). Our fabricated N-HPCS may become a potential candidate for high-performance adsorption materials.

Synthesis, characterization, and evaluation of antibacterial properties of silver/ carboxymethyl cellulose/ bacterial cellulose/ Clitoria ternatea extract aerogel composites

Food packaging for meat, processed food, and fresh food is often equipped with adsorbent pads to regulate moisture. However, most adsorbents are derived from synthetic polymer materials. There has been increasing demand for functional packaging materials that are not only durable, cost-effective, and well-designed, but also capable of extending the product shelf-life. Butterfly pea (Clitoria ternatea L.) flowers and silver nanoparticles have been reported to exhibit antibacterial activity in several studies. This study aimed to synthesize novel aerogel composites made of carboxymethyl cellulose (CMC), bacterial cellulose (BC), and C. ternatea flower extracts as adsorbent material in food packaging. BC was used as a reinforcing agent. The composites were synthesized by reacting silver solution and carboxymethyl cellulose, and then adding bacterial cellulose and C. ternatea extracts. Three different ratios of C. ternatea extract i.e. 0.5 %, 1 % and 2 % were used in this study (AT1, AT2, AT3). These aerogel composites were tested against four pathogenic bacteria i.e. Staphylococcus aureus, Eschericia coli, Pseudomonas aeruginosa, and Salmonella Typhimurium using disk diffusion and microdilution methods. The aerogel composites were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray fluorescence (XRF), Fourier-transform infrared (FTIR) spectroscopy, and color analysis. The results showed that AT3 had good antibacterial activity against P. aeruginosa, S. Typhimurium, and S. aureus with inhibition zones of 10.14 mm, 11.63 mm, and 7.69 mm, respectively, while composite AT2 had good inhibition against E. coli with the value of 9.82 mm. Equipped with good antibacterial activity, these aerogel composites have excellent potential to be used as adsorbent pads in food packaging to prolong the food shelf-life.

Extraction of nickel ions using nanoporous adsorbent material from waste glass

This study aims to create a porous glass adsorbent from waste glass to extraction nickel ions from its aqueous solution. The process involves converting waste glass to porous glass using 1:1:1:1 lime, sodium chloride, and sodium bicarbonate, followed by reacting with waste glass at 800 ˚C. The porous glass surface morphology, elemental composition, and functional groups, were analyzed using SEM, EDS, and FT-IR techniques.The outcome parameters used in this study are adsorbent dosage (10 g), contact time (150 min), heavy metal ion concentration (100 mg/l), and pH of 6. The adsorption capacity resulting from these parameters is 9.28 mg/g using the porous extract adsorbent for the extraction of nickel ions from its solutions. According to the findings. The proportion of Ni (II) ions extracted increased, coupled with a rise in the adsorbent dosage, heavy metal ion concentration, contact time, and pH. In addition, the Langmuir isotherm (R2 = 0.98,KL=0.072) has shown better performance than the Freundlich adsorption isotherm (R2 = 0.93,N=1.598) for the adsorption of the Ni(II) in this study.

Ag@AgCl/carbon nitride/graphene oxide three-dimensional nanocomposite constructed for efficient removal of organic dyes by synergistic adsorption-photocatalysis

The efficient removal of dye pollutants from wastewater is a significant and hotspot research. In this manuscript, Ag@AgCl nanoparticles were anchored on three-dimensional carbon nitride/graphene oxide (CN/GO) using an in-situ photoreduction strategy, and thus a novel (Ag@AgCl/CN/GO) was achieved. The results showed that the Ag@AgCl/CN/GO was a highly efficient adsorption and photocatalytic material for the removal of dye pollutants. The maximum adsorption capacity of malachite green (MG), methylene blue (MB), rhodamine B (RhB) and crystal violet (CV) can be reached as 324, 216, 148 and 112 mg g−1, and the photocatalytic degradation rate were 95 %, 83 %, 76 % and 93 % under irradiation for 60 min, which were greatly higher than some comparisons reported. The improved visible light, enhanced absorption and electron transfer in the Ag@AgCl/CN/GO three-dimensional structure were responsible to the highly efficient removal of dyes. Furthermore, the Ag@AgCl/CN/GO showed a good reusability in the cycling test. The constructed nanocomposite will be attractive for removing pollutants in wastewater.

Cellulose acetate-decorated and siloxane-modified hydrophobic melamine foam with excellent selectivity and durability for efficient oil/water separation

The construction of hydrophobic porous adsorption materials, which are cost-effective, green, stable, and efficient, are urgently demanded for the large-scale and effective oily wastewater treatment. Herein, a facile and low-cost two-step fabrication strategy of hydrophobic melamine foam (MF) was demonstrated, including cellulose acetate (CA) decoration and siloxane modification. Cellulose acetate initially assembled on the skeleton of MF with the aid of hydrogen bond formation between the hydroxyl groups of CA and imimo groups of MF. At an optimal concentration of CA, the as-prepared composite foam (CA/MF) exhibited good hydrophobicity. To further improve the oil/water selectivity, the above foam was enhanced by chemical vapor deposition (CVD) of methyltrimethoxysilane (MTMS). The successful silicification reaction between CA/MF and MTMS decreased the surface energy and improved the surface topological structure, leading to excellent hydrophobicity (water contact angle of 147.4°) and superoliophilicty. Such hydrophobized cellulose acetate/melamine foam (H-CA/MF) presented low density, favorable porosity (97.78%), and distinguished pore volume (88.66 mL/g), leading to a high oil adsorption capacity of up to 56.6 g/g. Due to the excellent mechanical elasticity of H-CA/MF, the oil absorption and recovery can be achieved easily by a simple manual adsorption-squeezing method and lab-made pump-assisted separation device with satisfactory recyclability. Moreover, H-CA/MF displayed marvelous stability and environmental adaptability in different harsh environment, further enlarging its practical application scenarios. Along with the green and cost-effective preparation process, the present study provides a facile strategy to fabricate hydrophobized melamine-based foam, which is of great significance for scalable and efficient oil/water separation.

Electrospinning of Sodium Alginate/Copper Oxide Nanofibrous Composite Membrane and Its Application of Cationic Dye Adsorption

AbstractDye wastewater is becoming one of the most significant sources of water pollution, and its impact on human survival is immeasurable. In this study, we successfully synthesized a nanofiber membrane with environmentally friendly and efficient properties using electrospinning of a mixture of sodium alginate (SA) and copper oxide (CuO) nanoparticles, aimed at effective dye removal. The adsorption performance of the SA/CuO nanofiber membrane was evaluated using the cationic dye methylene blue (MB). The maximum adsorption capacity of the nanofiber membrane was increased significantly with the addition of CuO nanoparticles, reaching a maximum value of 1633.4 mg g−1, almost twice as much as that of pure SA membrane. The adsorption kinetics follows the pseudo‐second‐order model, where chemisorption acts as the rate‐limiting step. The adsorption isotherm data indicate that the adsorption is monolayer. The nanofibrous membranes showed better dye removal under an alkaline environment. After four cycles of adsorption/desorption, the MB removal efficiency remained at 70.1% of the original adsorption capacity. The addition of CuO nanoparticles facilitated the adsorption of MB dyes, while the form of the nanofibrous membrane is easily recoverable and reusable. Therefore, the as‐prepared SA/CuO nanofibrous composite membrane is a potentially favorable adsorbent material for wastewater treatment applications.

Utilising date palm fibres as a permeable reactive barrier to remove methylene blue dye from groundwater: a batch and continuous adsorption study.

This study aimed to utilise cheap and abundantly available date palm fibre (DPF) wastes for the remediation of methylene blue (MLB) dye-contaminated groundwater. The DPF adsorbents were first prepared, followed by various characterisation analyses, including surface morphology, functional groups, and material structure. Subsequently, the DPF adsorbents were applied in the batch and continuous adsorption studies to assess the MLB dye removal from aqueous environments. The batch adsorption study achieved 98% maximum removal efficiency with a contact time, adsorbents dosage, initial pH, temperature, particle size, initial dye concentration, and agitation speed of 105min, 3g/L, 7.0, 45°C, 0.075mm, 50mg/L, and 150rpm, respectively. Langmuir was the best-fitted isotherm model depending on a higher correlation coefficient (R2 = 0.985), with a maximum monolayer dye adsorption capacity (qmax) of 54.204mg/g. Additionally, the second order was the best-fitted kinetic model (R2 = 0.990), indicating that MLB dye was removed through chemisorption. Besides, the positive enthalpy change (ΔH°) and negative Gibb's free energy (ΔG°) values verified the endothermic process and spontaneous adsorption. According to the impact analysis of initial dye concentrations and flow rates on the permeable reactive barrier (PRB) performance in the continuous adsorption study using the Thomas, Belter, and Yan models, the experimental results and predicted breakthrough curves reflected an excellent agreement (R2 ≥ 0.8767) and a sum of squared errors (SSE) ≤ 0.4834. In short, the results demonstrated DPF as an effective adsorbent material in PRB technology.

Preparation and NH3 adsorption behavior of porous magnesium oxychloride cement-based SrCl2

In addressing challenges in Selective Catalytic Reduction (SCR) systems in vehicles, the development of novel SrCl2 composite materials with high ammonia adsorption and structural stability is crucial. In this context, we employed the porous magnesium oxychloride cement (PMOC) as a carrier material, successfully fabricating a mesoporous PMOC-SrCl2 material via solution impregnation technology. Simultaneously, we employed various characterization techniques such as XRD, full-pore analysis, TG, SEM, TEM, and EDS to examine the material. We conducted static adsorption assessments on numerous candidate materials at 0.1Mpa and 293.15 K. The synthesized C3 series material (Mass ratio of SrCl2 to PMOC = 10:3), solution impregnated for 1 h, exhibited exceptional ammonia adsorption capacity (up to 38.01 mmol·g−1). Through model fitting of experimental data, we discovered that the adsorption process of this material closely aligns with the pseudo-second-order kinetic model and the Langmuir model. Over an adsorption time span of 180 min, the adsorption rate of the composite material increased by 129 % compared to pure SrCl2. In the cycle performance testing phase, we observed that the material exhibited no significant degradation in performance after undergoing 10 cycles of adsorption/desorption. This structurally stable, cost-effective, and readily accessible high-efficiency ammonia adsorption material undoubtedly possesses immense potential to solve the application challenges of ammonia adsorption materials within automotive selective catalytic reduction systems.

Construction and demolition waste as a low-cost adsorbent for water treatment: kinetics, isotherm, thermodynamics, and Fenton regeneration.

The present study proposes to investigate the feasibility of using construction and demolition waste (CDW) as an aqueous remediation agent through adsorption. The CDW, with and without chemical and thermal pre-activation, was evaluated to remove the methylene blue (MB) dye from the water solution. Variables interfering with adsorption processes, such as adsorbent dosage, solution pH, and particle size, were evaluated. The material was characterized by pHZPC, FTIR, XRD, SEM, EDS, and TG. The kinetic and equilibrium data better fitted the Elovich and Sips models, respectively. A maximum adsorption capacity of 18.62mgg-1 at 60°C was observed. Thermodynamic data indicated that adsorption occurred through a spontaneous and favorable process governed mainly by physical processes. The regeneration studies were carried out using processes based on the Fenton reaction, where the catalytic action of the iron naturally present in the CDW was evaluated. The results showed that the desorption balance was the main limiting factor for the effective regeneration of the saturated material. Adding Fe2+ to the system made this process suitable for the regeneration of the CDW and degradation of the pollutant in the aqueous phase. A regeneration efficiency of 65%, maintained practically constant during five adsorption-regeneration cycles, was observed. These results highlight the high potential of using CDWs as an adsorbent material.