Spherical Adsorbent Research Articles

Preparation of a Porous Spherical Adsorbent by Oil-In-Water-In-Oil Emulsion Polymerization for Phycocyanin Adsorption

ABSTRACT Phycocyanin is a protein with potential in food and medical applications. A porous spherical adsorbent was prepared by oil-in-water-in-oil emulsion polymerization. Oil and water phases containing surfactants and monomers, respectively, were emulsified, and the prepared emulsion was added to the oil phase to polymerize the porous spherical adsorbent. The concentration ratio of N,N-dimethylacrylamide and 2-dimethylaminoethylmethacrylate (DMAEMA) in the water phase was changed. The obtained spherical adsorbent had a size of about 150 μm and a water content of 90%, with macropores of several micrometers. Phycocyanin (20 kDa) of Nostoc commune was leached by the freeze and thaw method to prepare the solution. The adsorption data of the batch and column modes were evaluated by ordinary differential and partial differential equations, respectively, considering competitive adsorption, to obtain parameters of the mass transfer coefficient and saturated adsorption capacity. In the b\ sfer coefficient of phycocyanin decreased by about one-third, but the saturated adsorption capacity increased three-fold. In the continuous flow column, leached biomacromolecules other than phycocyanin had greater parameters of mass transfer and capacity. To prepare an adsorbent for the biomacromolecules, selective adsorption sites in the polymer matrix should be designed and prepared.

Al2O3-Encapsulated TiO2 flower-like spherical mesoporous material for efficient removal of PCl3 traces

Solar energy is considered the most promising sustainable green energy source. Currently, more than 95% of solar energy development and utilization is based on silicon, especially polysilicon. In the production of polysilicon, the PCl3 impurity content must be removed to the ppb level to ensure product performance. Al2O3 has been confirmed to be effective at removing PCl3 at ppm levels, however, it suffers from weak adsorption capacity, slow adsorption rate and low adsorption efficiency in the case of PCl3 in ppb levels. In this work, by encapsulating Al2O3 on TiO2, a flower-like spherical adsorbent ([Al2O3]3[TiO2]1) was prepared. The experimental results show that after introducing TiO2, the adsorption performance of [Al2O3]3[TiO2]1 for PCl3 in ppb levels is significantly improved, 34.1% higher than that before introducing TiO2. Five adsorption–desorption cycles indicate that [Al2O3]3[TiO2]1 has excellent regeneration property. Characterization analysis and density functional theory(DFT) simulations suggest that PCl3 interacts with the adsorbent primarily through charge transfer.

Construction of coal fly ash-based spherical grain adsorbents and their adsorption characteristics on phenolic compounds

Addressing the significant emissions and severe pollution hazards posed by coal fly ash waste in the coal chemical industry, as well as the challenges in recovering phenolic substances from coal chemical wastewater, this study utilized coal fly ash as a raw material to construct two types of spherical grain adsorbents: coal fly ash and coal gangue spherical grain (CFAGsg) and coal fly ash and pyrite spherical grain (CFAPsg). The adsorption performance of CFAGsg and CFAPsg towards phenolic substances in coal chemical wastewater was investigated. The research results demonstrated that CFAGsg and CFAPsg exhibited adsorption capacities of 20.31 mg/L and 30.42 mg/L for phenol, respectively, and maintained stable adsorption performance even after multiple regeneration cycles. Further analysis using kinetic, isotherm, and thermodynamic models, along with various characterization techniques, revealed that the adsorption of phenol onto CFAGsg and CFAPsg was primarily governed by physical and chemical adsorption, involving an endothermic reaction. Moreover, the study on the adsorption mechanism of phenol revealed that the adsorption behavior of CFAGsg and CFAPsg was mainly driven by pore filling, π-π stacking, and hydrogen bonding. Additionally, hydrophobic interactions were involved in the adsorption of phenol onto CFAGsg, while surface complexation forces played a role in the adsorption of phenol onto CFAPsg. Overall, the research findings provide vital theoretical support and practical application prospects for the high-value utilization of coal fly ash and the clean production of the coal chemical industry.

Optimization of batch process parameters for chromium (VI) removal from synthetic wastewater using eggshell–clay composite

In this study, a biodegradable spherical adsorbent bead was developed from eggshell (ES) and Bijoypur clay (BC) for the removal of hexavalent chromium from synthetic tannery wastewater. This Eggshell–Clay polymer composite (ES–BC) was made by incorporating them with PVA and alginate. To analyze the morphology and chemical composition of the adsorbent before and after the chromium adsorption, SEM, FTIR, XRD, and EDX were used. The impact of adsorption parameters such as adsorbent dosage (0.67–2.23 g/L), pH of the solution (1.5–9), contact time (10–240 min), initial Cr (VI) concentration (25–100 ppm), and solution temperature (25–65 °C), percentage clay in ES-BC adsorbent (0–40%) for Cr (VI) adsorption were investigated. The optimum value for adsorbent dosage, pH, contact time, initial Cr concentration, temperature, and clay to eggshell ratio was found 1.17 g/L, 1.5, 150 min, 58.2 ppm, 25 °C, and 80/20% respectively. The isotherm model was well-fitted to the Freundlich isotherm suggesting heterogeneous adsorption in multilayer on surface. The adsorption kinetics followed pseudo-second-order kinetics supporting the chemisorption process. Moreover, a decrease in enthalpy (H°) and negative Gibbs free energy (G°) with increased temperature indicated exothermic and spontaneous reaction. Therefore, this research investigated that the composite may serve as a viable option for treating Cr (VI) containing tannery effluent.

Highly selective granulation adsorbents for lithium recovery from gas field brine: Selectivity, kinetics and mechanism

Polyvinyl chloride (PVC)-based granulated adsorbents with high mechanical stability have proven effective for extracting lithium from salt lake brine on a commercial scale. However, granular materials with high adsorption selectivity for Na+/Li+ separation and long service life still remain a great challenge. Here, we prepared granulated spherical adsorbents by a phase conversion method using PVC as a binder; PEG, PMMA, PAN, and PAA as hydrophilic co-binders; and Li1.33Mn1.67O4 (LMO) as a powder adsorbent. Among these materials, P-PAA exhibited excellent hydrophilicity and excellent binder compatibility, facilitating the dispersion of LMO powders and ensuring high adsorption. Moreover, the mechanism of action of the PVC/PAA binders was first explored via experiments and simulations, which revealed that Li+ migration was promoted and occurred primarily on LMO rather than on binders, so nonselective adsorption decreased. Therefore, P-PAA demonstrated exceptional Li+ adsorption capacity (12.9 mg/g) and selectivity for Li+ (distribution factor of 1391.3 mL/g) over other coexisting cations and a separation factor of αNaLi= 718, which are greater than those of other adsorbents reported in the literature. Furthermore, the unique structure of P-PAA, which was obtained by interconnecting larger core pores (5–10 μm) and abundant smaller pores (0.5–1 μm), accelerated the water/ion transfer kinetics without causing powder leakage. Hence, the lifespan of these materials has been extended, as salt crystals or internal cracks did not form during long-term cyclic use, unlike in the case of other granules. All of the above factors made P-PAA effectively recover Li+ from Puguang gas brine, which contains a high sodium salt content and organic pollutants, with an efficiency of 98.4 %. All these properties demonstrate that P-PAA could be used in an appealing and competitive manner for industrial processes.

Experimental studies on the impact of adsorbent particle size on the adsorption chiller performance

Adsorption chiller dynamics and its effect on the performance are greatly influenced by the adsorbent particle size because they govern both the micro (intra-particle) and macro (inter-particle) heat and mass transfer resistances within the adsorber bed. The net effect of adsorbent particle size and shape on the overall cooling system performance is addressed here. Initial CFD analysis of columnar adsorber bed with silica gel + water as the working pair, assuming uniform spherical adsorbent, showed increased uptake capacity with smaller sized (0.23 mm radius) particles over bigger sized (0.8 mm radius) ones despite smaller vapor penetration depth of the former. Subsequently, the effect of adsorbent particle size and shape on the overall cooling system performance is investigated experimentally in a single-stage one-bed mode for RD 2060 (0.8 mm radius) and RD 3070 (0.23 mm radius) silica gel specimens. Though the smaller size of RD 3070 is favourable for the adsorption kinetics at the particle level, its non-spherical shape and highly non-uniform size distribution resulted in significantly lower permeability and thermal diffusivity of the packed adsorber bed, thus hindering the cyclic steady state throughput. For the same operating conditions, RD 2060 and RD 3070 yield a cooling capacity (CC) of 107 W and 22 W, respectively. Further, the coefficient of performance (COP) drops by 73% in the case of RD 3070. The present study indicates that the adsorber bed design must consider both the adsorbent size and shape, in addition to other system operational parameters to enhance performance indicators.

A spherical adsorbent produced from a bagasse biochar chitosan assembly for selective adsorption of platinum-group metals from wastewater

This study addresses the challenge of platinum-group metal scarcity by exploring the adsorption of these metals from industrial wastewater. An inexpensive adsorbent with selective platinum-group metal adsorption capacity, named chitosan/citric acid@diatomaceous earth-sugarcane bagasse (CTS/CA@DE-SBS), was newly synthesized. The material features a double coating of chitosan and diatomite on bagasse biochar, and it exhibits an excellent adsorption performance for platinum-group metals due to the synergistic effects of the biochar and chitosan-diatomaceous earth intercross-linked coatings. CTS/CA@DE-SBS achieved an 81 % adsorption efficiency and a static saturated adsorption capacity of 217 mg/g for Pt (IV) in water. Notably, the material exhibited selective adsorption properties for platinum-group metals dissolved in diverse aqueous solutions. The potential for the secondary recovery of platinum-group metals in complex aqueous bodies further underscores the significance of this adsorbent. In conclusion, this research introduces a promising solution for platinum-group metal shortages, offering a cost-effective and selective adsorbent with potential applications in the secondary recovery of these metals from industrial wastewater.

One-step room temperature synthesis of cyclotriphosphazene crosslinked tannic acid spherical adsorbent for efficient removal of cationic dyes in a wide pH range

A new tannic acid-based adsorbent (cyclotriphosphazene crosslinked tannic acid, TAH) for effective and selective removal of cationic dyes from aqueous solution was facilely synthesized employing rigid molecule hexacyclotriphosphazene (HCCP) as cross-linker at room temperature. The resulting typical sample TAH-3 was spherical with mean size of about 480 nm. Using cationic methylene blue (MB) as target dye, the adsorption property of TAH-3 was assessed systematically by investigating the effects of various key factors on the MB removal, including solution pH, adsorption time, con-existing ions, initial dye concentration and temperature. The experimental results showed that at 298.15 K and an initial MB concentration of 150 mg/L, the adsorption capacities of TAH-3 for MB ranged from 510 to 562 mg g−1 across a wide pH range of 3 to 10. The adsorption rate was very swift, and 72 % of equilibrium adsorption amount could be achieved within the initial 30 min. The effect of different valence co-existing ions on MB adsorption was quite different. The addition of monovalent Na+ could promote the MB adsorption, while the introduction of high-valence Ca2+ and Al3+ could inhibit the MB adsorption. After five adsorption–desorption cycles, TAH-3 presented a small loss in adsorption capacity for MB and maintained good structural stability. The remarkable adsorption of MB on TAH-3 might arise from the synergistic contribution of ion exchange, electrostatic attraction, H-bonding and π-π interaction. In addition, the TAH-3 spherical adsorbent could separate MB dye from binary mixed solution polluted by MB and anionic dye with a relative separation factor ranging from 281 to 11556. This work offers a facile and cost-effective synthetic route for negatively charged TA-based spherical adsorbent with high adsorption capacity and swift adsorption rate for cationic dye over a wide solution pH range.

Dual-use of sodium alginate to prepare sodium algenate -derived carbon dots sodium algenate hydrogel composite for Pb2+ removal

The effective mitigation of the environmental impact of heavy metal remains a significant scientific challenge. In this study, a novel and environmentally friendly approach has been proposed to fabricate three-dimensional (3D) functional composite materials for Pb(II) removal. The easy-to-recycle spherical adsorbent is prepared by the dual utilization of sodium alginate (SA) as a bio-source precursor for the synthesis of carbon dots (CDs) and as a natural framework for the formation of SA hydrogel. The abundant surface-active groups on the SA hydrogel not only provide additional adsorption sites for the aggregation of heavy metal ions but can also be readily cross-linked with CDs without chemical additives, and thereby offering a 3D porous structure for chelating metal ions. The resulting HL-5CDs adsorbent demonstrates an impressive adsorption capacity of 305.21 mg·g−1 for Pb(II). The adsorption mechanism involves both chemical reaction and diffusion, leveraging the porous structure and rich oxygen groups of the material. Notably, a pot experiment revealed that the as-prepared HL-5CDs could inhibit the bioavailability of Pb(II). This study introduces a green and straightforward method for creating high-performance adsorbents, showcasing potential applications in energy, cleaning, and the remediation of wastewater pollution.

Sodium alginate-modified alkali-activated eggshell/Fe3O4 nanoparticles: A magnetic bio-based spherical adsorbent for cationic dyes adsorption

Herein, a mixture of eggshell (ES) and magnetite nanoparticles (MNPs) was alkali-activated using NaOH/Na2SiO3 solution and then, impregnated with sodium alginate (SA) to prepare a magnetic bio-based adsorbent (namely SAAES/SA/MNPs) for the decontamination of water containing basic dyes, in particular, methylene blue (MB) and crystal violet (CV). The physicochemical properties of magnetic spheres of SAAES/SA/MNPs were characterized using XRD, FTIR, FESEM, EDX, elemental mapping, TEM, and zeta potential techniques. Dye adsorption equilibrium was studied experimentally at pH 8.0 and 25–55 °C, and a statistical physics multilayer model was applied to understand the removal mechanism of these dyes including the adsorption orientations on the adsorbent surface. The number of adsorbed dye molecules per functional group (n) of this bio-based adsorbent ranged from 0.70 to 0.91, indicating the presence of vertical and horizontal adsorption orientations for these organic molecules at all tested solution temperatures. The calculated saturation adsorption capacities (Qsat) were 332.57–256.62 mg/g for CV and 304.47–240.62 mg/g for MB, and an exothermic adsorption was observed for both adsorbates. The estimated adsorption energies (∆E) were < 25 kJ/mol, confirming that the SAAES/SA/MNPs–dye interactions were governed by physical forces as electrostatic interactions. This bio-based adsorbent was effectively regenerated using ethanol and it can be reused showing a removal of 71 and 74 % of MB and CV, respectively, after fourth adsorption–desorption cycles. Overall, the results of this article suggest the attractive performance of SAAES/SA/MNPs for removing basic dyes from aqueous solutions, thus highlighting the promising potential of this magnetic bio-based adsorbent for sustainable wastewater treatment at an industrial level.

Controllable microfluidic fabrication of honeycomb capsule adsorbent via the one-step titration-gel method

The hydrogel capsule adsorbent with honeycomb architectures was prepared via the one-step titration-gel method (OSTGM), which the casting solution contained polyvinyl alcohol (PVA), sodium alginate (SA) and tetraethyl orthosilicate (TEOS) were directly dripped into CaCl2 and H3BO3 aqueous mixture through a controllable microfluidic device. The microscopic morphology and adsorbed capacity of the SA-PVA-SiO2 capsules (SPSC) were absolutely depended on the parameter conditions during preparation. In this paper, at optimal synthesis situations [SA: PVA = 3: 7 (w: w), TEOS: (SA-PVA) = 2: 30 (v: w), the titration-gel distance was 14 cm and the feed flowed rate was 13 mL/h], the maximal removed capacity of the MB by the SPSC was 392.54 mg/g, and the SiO2 NPs accounted for 17.94 wt % of the polymers. The prepared SPSC, also, could work in overly acid and alkaline aqueous solutions (pH 1-13). The authors of this manuscript hoped this work would provide a corresponding guideline for the researchers who are aiming at preparing the spherical hydrogel adsorbents for waste water treatments.

Separatable polydopamine-coated cobalt-chitosan beads for Cr(VI) removal from wastewater with superior capacity

The discharge of hexavalent chromium [Cr(VI)] in industrial wastewater into the natural environment can seriously cause harm to the environment and human health. We modified chitosan (CS) with Co and polydopamine (PDA) to synthesize a spherical adsorbent (CS–Co/PDAHCl) for Cr(VI) removal from wastewater. Co doping can help CS–Co/PDAHCl maintain a high adsorption capacity (666.7 mg g-1) for Cr (VI) while retaining a complete bead shape after multiple recycling. In addition, CS–Co/PDAHCl can maintain 96% of its initial adsorption capacity after five adsorption cycles, demonstrating a strong regeneration ability. Under competitive conditions, the adsorption capacity of CS–Co/PDAHCl for Cr(VI) greatly exceed its adsorption capacity for Ni (II) and Mn (II). Because of the high selectivity of CS–Co/PDAHCl for Cr(VI), 1 kg of CS–Co/PDAHCl (cost approximately $31) could reduce the concentration of Cr(VI) in 87 m3 of secondary electroplating wastewater containing various complex components to the drinking water standard. Owing to the high selective adsorption capacity of CS–Co/PDAHCl for Cr(VI) and its good regeneration ability and expected economic feasibility, CS–Co/PDAHCl can find potential applications in removing Cr(VI) from real wastewater.

Zein-enhanced sodium alginate/thiostannate microsphere adsorbent Zein@SA/KBS for efficient removal of cesium from wastewater

Although efficient removal of Cs from wastewater is of great importance because of the nuclear energy sustainable development and public health, removing cesium is challenging for the high concentrations of sodium and potassium ions coexist. In this work, we synthesized the first novel bismuth-doped layered tin sulfide (KBS) and applied it to the efficient green adsorption of liquid cesium resources. KBS could reach the adsorption equilibrium for Cs+ within only 2 min with a theoretical adsorption capacity of 425.55 mg/g. Furthermore, the adsorption performance remained reliable after 10 cycles of use. The structure and properties of KBS were explained at the molecular level by DFT calculations, and the calculated results were in sound agreement with the experimental data. Meanwhile, in this study, the material was reinforced and shaped by the electrostatic interaction of Zein and sodium alginate hydrogel, and finally, Zein@SA/KBS spherical composite adsorbent was obtained. The problem of the difficult recovery of adsorbent and the secondary contamination was solved. The adsorption performance of Zein@SA/KBS on Cs+ was better than most composite adsorbents and showed reliable stability. Therefore, the new microspherical adsorbent (Zein@SA/KBS) has great potential for industrial application in removing radioactive cesium from wastewater.

Adsorption of anionic methyl orange dye on hybrid spherical silica in fixed-bed column

The textile sector is recognized for contributing the most dye residue, which is one of today's environmental challenges. It is a risky technique since wastewater includes toxins that can damage water sources and endanger human health and aquatic life. As a result, wastewater must be treated before disposal. There are numerous methods for removing dyes from wastewater, which categorized into chemical treatments, physical and biological procedures.. This study chose the continuous adsorption approach, which falls under the physical method since it is simple and effective. The oil-in-water emulsion was used to synthesize spherical silica (SSi) adsorbent in order to effectively remove and remediate one of the water-soluble anionic dyes, methyl orange dye (MO). The effect of influent concentration (10 to 50 ppm) and bed height (1.0 to 2.0 cm) on the continuous process was investigated. The breakthrough time exhibited an increase as the dye concentration decreased for all solutions that were examined. The removal efficiency of MO increased as the bed height increased, which can be attributed to the longer contact time between the MO dye and the adsorbent. The Thomas model exhibited a more favorable level of conformity to the data than Adams-Bohart and Yoon-Nelson. According to Thomas ' model, the maximum adsorption capacity (qo) increased as bed height decreased, and concentration increased. Moreover, Correlation values ranged from 0.882 to 0.979. Therefore, spherical silica adsorbent has the highest methyl orange dye adsorption capability at a bed height of 2.0 cm and concentration of 50 ppm.

Dry-column Vacuum Chromatographic Removal of Hg2+ from Wastewater Based on an Acridino-crown Ether-modified Spherical Silica Gel Adsorbent

Dry-column vacuum chromatographic technique is introduced for remediation of wastewater for the first time. A previously prepared chemically modified silica gel containing covalently immobilized Hg2+-selective acridino-crown ether selector molecules was used as an adsorbent. Removal of Hg2+ from highly contaminated river water was carried out to study practical applicability. Adsorption capacity, preconcentration factor, pH-sensitivity and selectivity in separation were determined. The adsorbent proved to be outstanding in selectivity, only Ag+ and Cu2+ interfered among 29 cations, was inert toward organic contaminants, exhibited regenerability and pH-independency between 3.0 ≤ pH ≤ 7.0. The proposed method showed a moderate efficiency in both adsorption (32 mg Hg2+ / 1 g adsorbent) and preconcentration (preconcentration factor of 100). A maximum 10 L of wastewater / 1 g adsorbent ratio is recommended as an upper limit for applicability. The described method showed a unique robustness and simplicity compared to conventional ion-chromatographic methods and an improved selectivity over physical interaction- or simple functional group-based adsorptions.

Marine oil spill remediation by Candelilla wax modified coal fly ash cenospheres

Biodegradable candelilla wax (CW) was creatively used for hydrophobic modification of coal fly ash cenospheres (FACs), a waste product from thermal power plants, and a new spherical hollow particulate adsorbent with fast oil adsorption rate and easy agglomeration was prepared. CW was confirmed to physically coat FACs and the optimum mass of wax added to 3 g of FACs was 0.05 g. From a series of batch scale experiments, CW-FACs were found to adsorb oil, reaching adsorption efficiency of 80.6% within 10 s, and aggregate into floating clumps which were easily removed from the water's surface. The oil adsorption efficiency was highly dependent on hydrophobicity of the used adsorbent, the adsorption of Venezuela oil onto CW-FACs was found to be a homogenous monolayer, and the capacity and intensity of the adsorption decreased as temperature increased from 10 to 40 °C. The Langmuir isotherm model was the best fit, with the maximum adsorption capacity achieved at 649.38 mg/g. CW-FACs were also found to be highly stable in concentrated acid, alkaline and salt solutions, as well as for spills of different oil products. Furthermore, the retention rate of the oil adsorption capacity of the CW-FACs after 6 cycles of adsorption-extraction was as high as 93.2%. Therefore, CW-FACs can be widely used, easily recycled, and reused for marine oil spill remediation, which is also a good alternative disposal solution for FACs.

Revealing Insights into the Mechanism of Hg0 Removal over MnO2 Hollow Sphere Adsorbents: Effect of Calcination Temperatures

In this study, MnO2 hollow spherical adsorbents were synthesized using the template approach, and the impacts of calcination temperatures on their physicochemical parameters and Hg0 removal ability were investigated. The adsorbent calcined at 300 °C (labeled as Mn300) demonstrated the highest performance; at 200 °C, the Hg0 removal efficiency reached over 90%. The presence of surface acid sites promoted the physisorption of Hg0 and compensated for the relatively weak oxidative ability, which made much of the Hg0 susceptible to capture on the adsorbent surface and consequently explained Mn300’s superior Hg0 capture capacity. The Mars–Maessen mechanism helped to understand the Hg0 capture pathways over Mn300, with Mn4+ and chemisorbed oxygen serving as the active species to oxidize Hg0 to HgO. Finally, Mn300 demonstrated reasonable recyclability and a rather weak gas-component adaptability, indicating that additional modification is required to improve the practical use of the adsorbent.

Removal of Methyl Orange Using Hybrid Spherical Silica Adsorbents

This study investigated the potential of adsorption behaviour of methyl orange onto hybrid spherical silica adsorbent. Removal of dye has been a problem worldwide and the study of removing dye through adsorption method is quite limited. This study aims to synthesize and characterize spherical silica (SSi) adsorbent and evaluate its adsorption capacity of it. The spherical silica adsorbent (SSi) was prepared using oil-in-water (o/w) emulsion polymerization modification where Tetraethyl Orthosilicate (TEOS) acts as the silica precursor. The physicochemical properties of SiNs were characterized using Fourier transform infrared (FTIR), field emission scanning (FESEM), nitrogen adsorption/desorption analysis (NAD), and transmission electron microscopy (TEM). The batch adsorption study for the methyl orange removal parameters such as pH (2-10 ) and agitation time (0-180 minutes). The experimental adsorption data were further evaluated using several adsorption kinetic models, namely pseudo-first-order, pseudo-second-order and Elovich kinetic models. The diffusion kinetics model includes the Weber-Morris plot, Fick’s Law equation and Boyd plot. The result shows that the spherical silica (SSi) adsorbent at pH 2 has the highest adsorption capacity amongst another adsorbent towards methyl orange which is 45.05 mg/g. Furthermore, the equilibrium time for methyl orange adsorption onto SSi was 120 min. The data fitted into a pseudo-second-order kinetic model indicating chemical adsorption, limited by film diffusion.

Synthesis of Spherical Composite CMC-LTO-EGDE-ME for Lithium Recovery from Geothermal Water

In this study, ethylene glycol diglycidyl ether (EGDE) and melamine (ME) were used to prepare a spherical composite material CMC-LTO-EGDE-ME through the strategy of cross-linking reaction of biodegradable sodium carboxymethyl cellulose (CMC) with Li2TiO3 (LTO) to improve the cycle stability of the adsorption-desorption for lithium recovery. In the geothermal water at 333.15°K, the adsorption capacity of the spherical composite adsorbent for lithium-ion is 12.02 mg/g, and the adsorption equilibrium time is 8 h. There is a good selectivity of Li+ (Kd = 3.7 × 103) and high separation factors between Li+ and Na+, K+, Cs+ and Ca2+ (between 39.17 and 181.97). Studies on adsorption kinetics and adsorption isotherm showed that composite material’s adsorption process was obtained from the pseudosecond-order kinetics and the molecular diffusion model. It was found that the composite material has broad applications in lithium recovery from geothermal water.

Effective Pb2+ adsorption by calcium alginate/modified cotton stalk biochar aerogel spheres: With application in actual wastewater

A spherical composite aerogel adsorbent (CA/KCB aerogel) with excellent Pb2+ adsorption performance was prepared by sol-gel method using calcium alginate (CA) and KMnO4 modified cotton stalk biochar (KCB). The preparation parameters of CA/KCB aerogel were optimized by response surface methodology. The physicochemical properties and Pb2+ adsorption characteristics of CA/KCB aerogel were systematically investigated. The CA/KCB aerogel before and after Pb2+ adsorption was characterized by SEM, EDS, FTIR and XRD, and the adsorption mechanism was discussed. The optimal preparation parameters of CA/KCB aerogel are: the dosage of KCB was 6 g/L, the mass concentration of sodium alginate and CaCl2 was 3% and 1% respectively. CA/KCB aerogel was rich in oxygen-containing functional groups, exchangeable cations and interconnected pores, and can exist stably in aqueous solutions with a wide pH range (2−12). The data of adsorption kinetics and adsorption isotherms can be well fitted by the pseudo-second-order model and Langmuir model, respectively. The maximum adsorption capacity of Pb2+ was 664.6 mg/g. The adsorption process was an endothermic reaction dominated by monolayer chemisorption. The binding of CA and KCB in aerogel can promote the adsorption of Pb2+ synergistically. Finally, CA/KCB aerogel was directly applied to the treatment of electroplating wastewater. The coexisting heavy metals (Pb, Cu and Zn) in the wastewater can be effectively removed when the adsorbent dose was 35 g/L. The conclusion is that CA/KCB aerogel has a promising application prospect as adsorbent for heavy metal removal.