Adsorption Equilibrium Time Research Articles

Facile Preparation of Magnetic Chitosan Carbon Based on Recycling of Iron Sludge for Sb(III) Removal

In this study, following the concept of “treating waste with waste”, magnetic chitosan carbon (MCC) was developed through the pyrolysis of chitosan/iron sludge (CHS) beads created using an embedding method in a closed environment for antimony removal. The results indicate MCC has a good magnetic recovery rate and that its magnetic saturation strength can reach 33.243 emu/g. The iron proportion and acid resistance of MCC were all better than those of CHS, and at 25 °C, its adsorption saturation capacity improved from 24.956 mg/g to 38.234 mg/g. MCC has a quick adsorption equilibrium time, and in about 20 min, 90% of the final equilibrium capacity can be achieved. The primary mechanism of Sb adsorption by MCC is the formation of an inner sphere complex between Fe-O and Sb, while surface complexation, hydrogen bonding, and interaction also play a function. Thus, MCC, a lower-cost and greener adsorbent for Sb removal, has been made using iron sludge. This enabled it to utilize iron sludge as a resource and served as a reference for the sustainable management of water treatment residuals.

Adsorption and photocatalytic degradation activities of a hybrid magnetic mesoporous composite of α-Fe2O3 nanoparticles embedded with sheets-like MgO

Crystal violet (CV), identified as a potential carcinogen, is a synthetic dye prevalent in wastewater from textile and paint industries. Therefore, the current study demonstrates that the hybrid composite of mesoporous magnetic α-Fe2O3 nanoparticles @ sheet-like MgO (Fe2O3@MgO) can be employed as a potential effective sorbent and photocatalyst for CV-removal from polluted water. A comparative study was systematically performed on the CV-removal using MgO and Fe2O3@MgO composite. The physicochemical, textural, and structural properties, morphological features, and elemental composition of mesoporous Fe2O3@MgO composite were intensively investigated. Batch trials were performed to optimize the sorption conditions. The highest CV-uptake efficiency was detected at pH 9 within the adsorption equilibrium time of about 30 min, where the maximum capacity of Fe2O3@MgO was 50.8 mg/g. Under UV irradiation, the Fe2O3@MgO photocatalyst exhibited a high efficiency and fast response toward CV-removal. The mechanism of CV removal was researched through zeta potential (ZP), bandgap, and density functional theory (DFT) calculations. The outcome demonstrated that mesoporous Fe2O3@MgO sorbent/photocatalyst could be recycled and reused ten times, making it a cost-effective solution for removing CV-dye from wastewater. This manuscript suggested that mesoporous Fe2O3@MgO composite is an efficient adsorbent/photocatalyst for fast, affordable, and efficient decontamination of CV-dye from wastewater.

A sodium alginate gel bead adsorbent doping with amidoxime-modified hydroxyapatite for the efficient adsorption of uranium

In this work, the modified‑sodium alginate gel beads were prepared by sol-gel method. Due to the presence of water channels in the sodium alginate gel bead, amidoxime groups and PO43− were exposed to the surface of the adsorbent to the maximum extent, resulting in the excellent adsorption capacity of modified‑sodium alginate gel beads. The introduction of amidoxime-modified hydroxyapatite significantly improved the adsorption capacity and the adsorption rate of the gel beads. The adsorption capacity increased from 308.7 to 466.0 mg/g and the adsorption equilibrium time was shortened from 300 min to 120 min. The modified‑sodium alginate gel bead possessed the advantages of short adsorption time, high adsorption efficiency and large adsorption capacity, which could be regarded as a potential adsorbent for uranium. Moreover, the uranium removal ability on the modified gel beads was mainly attributed to the Coulomb force between PO43− and uranium and the complexation between uranium and amidoxime groups. In summary, this work would provide a new idea for the modification and application of sodium alginate-based materials.

Adsorption and Desorption Behavior of Partially Hydrolyzed Polyacrylamide on Longmaxi Shale

Large-scale volumetric fracturing is generally used during shale gas development. The return rate of fracturing fluid is low, and a large amount of slickwater is retained in the reservoir. The adsorption and desorption of partially hydrolyzed polyacrylamide (HPAM), an additive commonly used in slickwater, on the surface of shale was studied using Longmaxi shale from the Sichuan Basin. The experimental results showed that the mass ratio of the HPAM solution to shale reached saturation adsorption at 20:1 when the concentration of HPAM solution was 1000 mg/L and 25:1 when the concentration of HPAM solution was 500 mg/L. The mass ratio of the HPAM solution to shale was fixed at 25:1, and the adsorption equilibrium was reached at a HPAM concentration of 1000 mg/L when the aqueous solution temperature was 30 °C and 800 mg/L when the aqueous solution temperature was 60 °C. The Langmuir adsorption model yielded a better fit than the Freundlich adsorption model. The adsorption equilibrium time at 30 °C was at 60 min for a HPAM concentration of 500 mg/L, while for a concentration of 1000 mg/L, it was at 90 min. The adsorption equilibrium time at 60 °C was 40 min for a HPAM concentration of 500 mg/L, whereas it was 60 min for a HPAM concentration at 1000 mg/L. The pseudo-second order (PSO) kinetics model yielded better fits than the pseudo-first order (PFO) kinetics model. The adsorption of HPAM on shale was strong, and the adsorbed HPAM resembled cobwebs adhering to the shale surface. HPAM on the surface of shale after adsorption was able to resist the desorption capacity of water. However, when the amount of adsorbed HPAM on shale increased significantly, the amount of residual HPAM on the surface of the shale decreased rapidly during desorption in deionized water. The desorption of HPAM on the shale surface followed a modified desorption model. The higher the concentration of HPAM adsorbed on the shale surface was, the easier it was to desorb and the easier it was to be removed from the shale.

Length-controlled hydrophobic CF3-COF as a highly efficient absorbent coating for dual-mode solid-phase microextraction of sixteen polycyclic aromatic hydrocarbons in water samples

Polycyclic aromatic hydrocarbons (PAHs), a group of seriously hazardous environmental contaminants, have attracted extensive attention due to their carcinogenicity, genotoxicity, mutagenicity, and ubiquity. In this work, the excellent hydrophobic trifluoromethyl-enriched covalent organic framework (CF3-COF) was designed and synthesized as coating of solid-phase microextraction (SPME). The CF3-COF offered a high adsorption selectivity for PAHs, which could be attributed to the multiple interactions between the CF3-COF and PAHs, including hydrophobicity interaction, π-π and H bond interactions. Furthermore, headspace (HS) and direct immersion (DI) dual-mode solid-phase microextraction (HS/DI-SPME) were innovatively integrated as a dual-mode extraction by varying the length of SPME coating on stainless-steel, which could simultaneously and efficiently extract 16 PAHs with different volatile. Amazingly, the proposed strategy achieved fast adsorption for PAHs and shortened the adsorption equilibrium time to 15 min. By further integrating with gas chromatography tandem mass spectrometry (GC–MS/MS), PAHs could be detected in the range of 0.008–0.16 ng mL−1 with a quantitative limit of 0.029–0.47 ng mL−1, respectively. The recoveries of PAHs in water samples ranged from 80.84 to 117.67 %. This work indicates that the dual-mode CF3-COF-SPME is a promising candidate for the enrichment of multiple hazardous substances in complicated samples.

Thio-groups decorated covalent triazine polyamide (TTPA) for Hg2+ adsorption: Efficiency and mechanism

In this work, the thio-modified covalent triazine polyamides, TTPA-1 (1.5/1) and TTPA-2 (1/1), were successfully synthesized from the diester containing S and melamine, and applied to the adsorption of Hg2+ in the aqueous solution. We have systematically investigated the factors that can affect the adsorption process, such as the dosage of the adsorbent, the contact time, the temperature of the heavy metal solution, the initial concentration of the ions, the pH, the co-existing substances, and the desorption. The pseudo-second-order kinetic model can describe the adsorption of Hg2+ well, and the equilibrium adsorption time is 180 min, respectively. The most appropriate adsorption isotherm model is Langmuir, and the maximum Hg2+ adsorption capacities calculated at 25°C are 685 (TTPA-1) and 657 (TPPA-2) mg g−1. Repeatable experiments have shown that it can be reused more than 10 times without any loss. The adsorption mechanism of TTPA-1 (-2) was elucidated by combining experimental results, spectral characterization (SEM and XPS, etc.) and the density-functional-theory (DFT) calculations. These results indicate that TTPA-1 (-2) could have a good potential for the removal of the Hg2+ metal ions from wastewater.

Liquid-waste derived magnetic porous carbon sphere for effective removal of tetracycline from aqueous solution

Effective removal of tetracycline (TC) from wastewater is highly important while still faces challenges especially in adsorption capacity. Herein, a novel N-doped magnetic porous graphitic carbon sphere (N-MPGCS) adsorbent was fabricated by a green strategy using tannic acid (TA) as organic ligand and stainless steel pickling wastewater as metal source. Melamine was also introduced to increase nitrogen-containing functional groups. Among the obtained carbon spheres, N-MPGCS1–800 sample shows a large specific surface area (up to 922.78 m2 g−1), appropriate O/N functional groups, suitable sp2 carbon, and good magnetic responsivity. Benefiting from these merits, this optimal material exhibits a high Langmuir adsorption capacity (1005.5 mg g−1 at 45 °C) for TC, fast adsorption kinetics (5 min for adsorption equilibration time at 50 mg L−1), and good applicability towards pH (3−10) and co-existing ions. Besides, the excellent magnetism permits the convenient and rapid recovery of adsorbent from the adsorption system. Moreover, the high TC removal ratio (92.3% after three cycles) presents its outstanding regeneration. Adsorption studies and characterizations show that H-bond, π-π stacking, metal-organic complexation interactions, and pore-filling effect contribute to the adsorption together. In addition, N-MPGCS1–800 also shows good removal on enrofloxacin, moxifloxacin, and norfloxacin. This work proves that N-MPGCS material can serve as a potential adsorbent, and more importantly, it gives a new path for mining industrial waste to produce high-effective magnetic carbon materials.

Application of a novel polymer cross-linked with magnetite for efficient norfloxacin adsorption at a wide pH range

Nowadays, NOR-containing wastewater has placed huge pressure on global ecology. In this study, a chemically-modified chitosan-based polymer was cross-linked with magnetite to prepare a novel magnetic composite adsorbent named Fe3O4/CS-P(AM-SSS) for norfloxacin (NOR) removal. The preparation conditions were optimized by single factor experiments and response surface methodology. A series of characterization analyses were carried out on the morphology, structure, and properties of Fe3O4/CS-P(AM-SSS), verifying that Fe3O4/CS-P(AM-SSS) was successfully prepared. Batch adsorption experiments showed that NOR was efficiently removed by Fe3O4/CS-P(AM-SSS), with a broad pH applicability of 3–10, short adsorption equilibrium time of 60 min, maximum adsorption capacity of 268.79 mg/g, and high regeneration rate of 86% after eight adsorption-desorption cycles. Due to the three-dimensional network structure and abundant functional groups provided by modified chitosan polymer, the superior adsorption capability of Fe3O4/CS-P(AM-SSS) was achieved through electrostatic interaction, π-π stacking, hydrophobic interaction, and hydrogen bonding. Adsorption process was exothermic and well fitted by the pseudo-second-order kinetic model and the Langmuir isothermal model. The presence of cations had a slight inhibitory effect on NOR adsorption, while humic acid nearly had no effect. In model swine wastewater, 90.3% NOR was removed by Fe3O4/CS-P(AM-SSS). Therefore, with these superior characteristics, Fe3O4/CS-P(AM-SSS) was expected to be an ideal material for treating NOR-containing wastewater in the future.

Insight into the synergism of residual carbon and slag particles in coal gasification fine slag on porous composites preparation for CO2 capture

Coal gasification fine slag (FS), as a by-product of coal gasification process, contains residual carbon (RC) and slag particles (SP). The two components can be used as raw materials to prepare porous materials. Whereas, during simultaneous utilization of RC and SP, their synergistic mechanism remains unclear. The research on the mechanism is beneficial for synthesis of the high performance CO2 adsorbent. Herein, FS was treated by chemical activation followed by hydrothermal treatment to prepare porous composite material (FS-25-HA-HT) which had high surface area of 2194 m2/g and pore volume of 2.095 cm3/g. After chemical activation, the SP could be completely dissolved in alkali solution within around 20 min. The adsorption of porous carbon in alkali solution and strong electrostatic attraction from oxygen groups with the Si, Al-containing groups led to the increase of the concentration of Si (9825 ppm) and Al (2986 ppm) in subnatant during hydrothermal treatment. Thus, the aluminosilicate could deposit on the surface of porous carbon and pile up to form new crystal layer, which could increase the surface area and the CO2 adsorption capacity. The adsorbent met both high uptake (5.32 mmol/g at 0 °C) and fast adsorption kinetics (adsorption equilibrium time of 3 min.). The clarification of synergism during simultaneous utilization of RC and SP offers new routes to prepare high performance adsorbent.

Synergistic removal performance and mechanism of Cd(II) and As(III) from irrigation water by iron sulfide-based porous biochar.

Since Cd(II) and As(III) have extremely opposite chemical characteristics, it is a huge challenging to simultaneously remove these two ions from aqueous solutions. Therefore, a novel iron sulfide-based porous biochar (FSB) was synthesized and used to evaluate its Cd(II) and As(III) removal performance and mechanisms. The characterization and batch experiments results indicated that FeS was successfully loaded on the surface of biochar and increased its adsorption sites. The iron sulfide-based porous biochar was very favorable for the removal of Cd(II) and As(III) in the weakly acidic environment. The maximum adsorption of Cd(II) and As(III) by FSB was 108.8 mg g-1 and 76.3 mg g-1, respectively, according to the Langmuir and Freundlich isothermal adsorption model, and the adsorption equilibrium time was 12 h and 4 h, respectively, according to the pseudo-second-order kinetic model. In the coexisting ion system, Cd(II) adsorption was suppressed by Ca2+, Mg2+, and humic acid, but enhanced by PO43- and As(III). As(III) adsorption was inhibited by PO43- and humic acid. Precipitation and complexation are the predominant adsorption mechanisms of Cd(II) and As(III), which contribute to the formation of Cd-O, Fe-O-Cd, As-O, Fe-O-As, ternary complex Cd-Fe-As, and stable compounds FeAsO4·2H2O and CdS. Therefore, The iron sulfide-based porous biochar can be an efficient and environmentally friendly candidate for the treatment of Cd(II) and As(III) co-polluted irrigation water.

Evaluation of Chlorella vulgaris biosorption capacity for phosphate and nitrate removal from wastewater

High wastewater production rates during the past few decades are mostly attributable to anthropogenic activities. The main components leading to the nutrient enrichment of natural water bodies are such as nitrogen, phosphorus, and other minerals. The main focus of this research was to assess the ability of using Chlorella vulgaris algae, a potent and environmentally benign material, to eliminate phosphate and nitrate ions from wastewater. FTIR results showed that the biologically active molecules that facilitate the binding of phosphate and nitrate ions unto the C. vulgaris are C=C and N–H amid. The ideal equilibrium time for adsorption was 24 h with an optimum pH of 7 and the mass ratio of algae and different anions concentration was 80%. Freundlich isotherm model was the best-fitted isotherm. Moreover, the results of the experiment fit more closely with the pseudo-second-order kinetic model than other models. Elovich kinetic model data for both ions showed that the adsorption rate was much higher than the desorption rate. The growing popularity of biosorbents in treating wastewater has led to an improvement in their affordability and availability, and C. vulgaris may now represent an environmentally friendly choice from an environmental, and economic standpoint.

Design of ion-imprinted amino-modified chitosan for selective chromium (Ⅲ) ion removal

Green ion-imprinting technique was applied to construct a Cr(III) ion-imprinted absorbent material from an amino functionalized chitosan derivative. First, nitrogenous organic compounds (GACS) as functional monomer is synthesized by a Schiff base reaction followed by a grafting reaction. In the end, imprinting was completed by cross-linking with epichlorohydrin (ECH) in aqueous media and eluting the coordinated ions with hydrochloric acid to obtain chromium-imprinted polymers (Cr(III)-IIP) with pores. The relevant parameters of the imprinting system were explored, and the superior polymer (Cr(III)-IIP9) has an excellent adsorption capacity 385.89 mg/g, wide pH range adsorption, good adsorption rates and equilibrium times (≤120 min) for Cr(III) ion. Additionally, the kinetic study is best defined in terms of pseudo-second order, while the Freundlich isotherm model fits the data well. Competitive adsorption of the quaternary system of Cr(III)/ Cd(II)/ Ni(II)/ Cu(II) were also investigated, it demonstrated a greater affinity for the Cr(III) ion than other ions. Hence, the imprinting materials prepared by amino functionalized chitosan enhances the adsorption of Cr(III) ions in the simulation of actual water sample. The adsorption mechanism accords with the hard and soft acid and base theory (HSAB), which is expected to be is utilized for the separation of Cr(III) ions in the environment.

The Adsorption of Pb(II) from Aqueous Solution Using KOH-Modified Banana Peel Hydrothermal Carbon: Adsorption Properties and Mechanistic Studies.

Adopting banana peel as a raw material, the adsorption properties of banana peel hydrothermal carbon modified with a KOH solution for lead ions in aqueous solution were studied. The surface structure and functional groups of the modified hydrothermal carbon were analyzed by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy, the Brunner-Emmet-Teller (BET) method, element analysis, and Raman spectroscopy. The results showed that an adsorption capacity of 42.92 mg/g and a removal rate of 86.84% were achieved when the banana peel hydrothermal carbon was modified with a KOH solution of 0.5 mol/L, with a pH of 6 and a solid-liquid ratio of 1 g/L. The equilibrium adsorption time for lead ions in solution being adsorbed using KOH-modified hydrothermal carbon was 240 min, the adsorption process satisfied the quasi-second-order kinetic model and the Redlich-Peterson isotherm equation, and the equilibrium removal efficiency was 88.62%. The adsorption of lead ions using KOH-modified hydrothermal carbon is mainly chemical-physical adsorption.

Integration of covalent organic frameworks and molecularly imprinted polymers for selective extraction of flavonoid naringenin from grapefruit (Citrus × paradisi Macf.) peels

Grapefruit (Citrus × paradisi Macf.) peel, a by-product of the citrus-processing industry, possesses an important economic value due to the richness of bioactive compounds. In this study, boron-linked covalent organic frameworks integrated with molecularly imprinted polymers (CMIPs) were developed via a facile one-pot bulk polymerization approach for the selective extraction of naringenin from grapefruit peel extract. The obtained CMIPs possessed a three-dimensional network structure with uniform pore size distribution, large surface areas (476 m2/g), and high crystallinity. Benefiting from the hybrid functional monomer APTES-MAA, the acylamino group can coordinate with the boronate ligands of the boroxine-based framework to form B-N bands, facilitating the integration of imprinted cavities with the aromatic skeleton. The composite materials exhibited a high adsorption capacity of 153.65 mg/g, and a short adsorption equilibrium time of 30 min for naringenin, together with favorable selectivity towards other flavonoid analogues. Additionally, the CMIPs captured the template molecules through π–π* interaction and hydrogen bonding, as verified by FT-IR and XPS. Furthermore, they had good performance when employed to enrich naringenin in grapefruit peels extract compared with the common adsorbent materials including AB-8, D101, cationic exchange resin, and active carbon. This research highlights the potential of CMIPs composite materials as a promising alternative adsorbent for naringenin extraction from grapefruit peel.

Synthesis of Microspheres Printed with Metals and Investigation of Their Detection Performance Against Some Metals by ICP-OES

In this study, ion-imprinted polymers were prepared. These polymers can be used for the selective removal of Cu(II) ions from aqueous solutions. To this end, (E)-2-hydroxy-5-((vinylphenyl)diazonyl) benzaldehyde was used as a functional monomer in the synthesis stage of the polymeric adsorbent. Cu(II) imprinted poly[Cu(C15H11N2O2)] microspheres have been synthesised by dispersion polymerisation technique through interaction of the template molecule Cu(II) ion with the functional monomer. The specific surface area of Cu(II) imprinted poly[Cu(C15H11N2O2)] microspheres was 374.26 m2/g. The swelling rate was 80%. The maximum adsorption capacity, the optimum pH and the adsorption equilibrium time were determined to be 153.03 mg/g, in the 8-10 range and 30 min, respectively. The relative selectivity coefficients of the imprinted microspheres were found to be 13.09, 57.88, 44.719 and 35.006 for Cu(II)/Ni(II), Cu(II)/Pb(II), Cu(II)/Zn(II) and Cu(II)/Co(II), respectively. These results showed that the Cu(II)-imprinted microspheres were more selective with respect to Cu(II) ions. Reproducibility studies showed that Cu(II) imprinted poly[Cu(C15H11N2O2)] microspheres can be used repeatedly without significant decrease in adsorption capacity.

Fabrication of silica/calcium alginate nanocomposite based on rice husk ash for efficient adsorption of phenol from water.

The current work discusses the synthesis of three different solid adsorbents: silica nanoparticles derived from rice husk (RS), calcium alginate beads (AG), and silica/alginate nanocomposite (RSG). The fabricated solid adsorbents were characterized by using different physicochemical techniques such as TGA, XRD, nitrogen adsorption/desorption analysis, ATR-FTIR, pHPZC, SEM, and TEM. The adsorption efficiencies of the prepared solid adsorbents were considered for the removal of phenol as a selected hazardous pollutant. Because of its improved adsorption capacity and environmentally friendly character, a composite made of biosilica nanoparticles and naturally occurring alginate biopolymer by click chemistry is significant in environmental treatment. Adding silica nanoparticles to the alginate biopolymer hydrogel has many advantages, including increased surface area, easier recovery of the solid adsorbent, and additional surface chemical functional groups. The silica/alginate nanocomposite showed surface heterogeneity with many chemical functional groups present, whereas silica nanoparticles had the highest surface area (893.1 m2 g-1). It has been found that the average TEM particle size of RS, AG, and RSG was between 18 and 82 nm. RSG displayed the maximum adsorption capacity of phenol (100.55 mg g-1) at pH 7 and 120 min as equilibrium adsorption time. Adsorption of phenol onto the solid adsorbents fit well with a nonlinear Langmuir isotherm with favorable adsorption. Kinetic and thermodynamic studies prove that the adsorption process follows a pseudo-second-order kinetic model, endothermic process, physical, and spontaneous adsorption. Sodium hydroxide is effective in desorbing 94% of the loaded phenols, according to desorption investigations. Solid reusability tests showed that, after seven cycles of phenol adsorption/desorption, RSG lost only 8.8% of its adsorption activity.

Preparation and dye adsorption properties of activated carbon/clay/sodium alginate composite hydrogel membranes.

A hydrogel membrane was prepared using activated carbon and sodium dodecyl sulphate modified montmorillonite clay incorporated into sodium alginate polymer. The activated carbon was prepared from a locally available susbine plant. The physiochemical characteristics of the synthesized hydrogel membrane were investigated using FTIR, SEM, EDX, and TGA techniques. The performance of the membrane was evaluated as an adsorbent by methyl red adsorption from water. The adsorption behavior of the hydrogel membrane was investigated under varying conditions of pH (2-10), membrane dose (0.0025-0.015 mg g-1), equilibrium adsorption time (30-360 minutes), solution temperature (25-45 °C) and dye concentration (100-500 mg L-1). The maximum adsorption capacity of the hydrogel membrane was 248.13 mg g-1. The kinetics of methyl red adsorption on hydrogel membrane best followed the pseudo-second order (PSO). The equilibrium adsorption results suggested that it obeyed the Freundlich isotherm very closely (R2 = 0.994). The thermodynamics of methyl red adsorption on the hydrogel membrane revealed that the adsorption was spontaneous (ΔS° = 16.15 kJ K-1 mol-1), favorable (ΔG° = -3.51 kJ mol-1), and endothermic (ΔH° = -1.48 kJ mol-1) in nature. These investigations suggested that the fabricated hydrogel membrane could be suitably used for methyl red adsorption from the solution.

Efficient recovery of gold from solution with a thiocyanate-modified Zr-MOF: adsorption properties and DFT calculations.

The design and development of new large-capacity and selective materials for extracting rare precious metals via electronic waste is practically essential. In this paper, a new efficient UiO-66-NCS has been obtained as a consequence of the modification of the classical Zr-MOF (UiO-66-NH2), and its ability to recover gold has been investigated. These batch results adequately illustrated that UiO-66-NCS exhibited good adsorption capacity (675.5 mg g-1) and exceptional selectivity. In addition, UiO-66-NCS achieved faster adsorption equilibrium times of about 120 min. Adsorption kinetics and isotherms demonstrated that the pseudo-second-order adsorption scheme and a Langmuir-type procedure were shown by the adsorption of Au(III) on UiO-66-NCS. Characterized by pH effect experiments, TEM, XRD, and XPS, the adsorption of UiO-66-NCS with Au(III) relies on coordination, which further results in reduction, and the generated Au(0) is uniformly dispersed in the MOF. The adsorbent has considerable advantages for cyclic regeneration. Finally, DFT fitting results showed that the adsorption binding energy of UiO-66-NCS with [AuCl4]- was -8.63 kcal mol-1 for the adsorption process. UiO-66-NCS is likely to be an ideal substance for gold recovery.

Adsorption and Kinetic study of priority organic pollutant phenol from aqueous waste using Activated carbon

Many organic compounds present in industrial and domestic wastewater are carcinogenic in nature. Removal of these organic compounds from waste waters has become a great challenge to waste water treatment technologies as many of them are non-biodegradable in nature. Adsorption on activated carbon has emerged as an efficient and economically viable technology for the removal of a broad spectrum of toxic organic compounds from domestic and industrial waste water. The adsorption of hazardous organic compounds on activated carbon has been the subject of research for the past three decades. In the present study, kinetic study for adsorption of some priority organic pollutants like phenol on activated carbon, was studied at laboratory scale. Series of experiments were carried out to determine kinetics for adsorbate, when present in aqueous solution as a single component. The commercially available bituminous coal based activated carbon Filtrasorb-400 was used as an adsorbent. A simplified interpretation of the kinetic data based on Langmuir theory has been used. The kinetics performed gives the adsorption equilibrium time. The adsorption and desorption rate constants were evaluated from the graph.

Selective Separation of Zr(IV) from Simulated High-Level Liquid Waste by Mesoporous Silica.

The efficient separation of Zr(IV) ions from strong acidic and radioactive solutions is a significant challenge, especially in the context of the aqueous reprocessing of nuclear fuels. The complexity of such solutions, which are often characterized by high acidity and the presence of radioactive elements, poses formidable challenges for separation processes. Herein, several mesoporous silicas (HMS, MCM-41, KIT-6, and SiO2-70 Å) with excellent acid and radiation resistance properties were employed as sorbents to remove Zr(IV) ions from simulated high-level liquid waste. The batch experiments were designed to investigate the influence of adsorption time, HNO3 concentration, initial Zr(IV) concentration, adsorbent dosage, and temperature on the adsorption behavior of Zr(IV). The results indicate that the adsorption equilibrium time of mesoporous silica materials was approximately 8 h, and all the adsorption processes followed the pseudo-second-order kinetics equation. The isotherms of Zr(IV) adsorption by KIT-6 exhibited good agreement with the Langmuir model, while the Freundlich model could be utilized to fit the adsorption on HMS, MCM-41, and SiO2-70 Å. The adsorption capacity of MCM-41 for Zr(IV) in 3 mol/L HNO3 was 54.91 mg/g, which is three times the adsorption capacity reported for commercial silica gel (17.91 mg/g). The thermodynamic parameters indicate that the adsorption processes for zirconium are endothermic reactions. Furthermore, the mesoporous silicas exhibited a pronounced selectivity in the adsorption of Zr(IV) within a simulated high-level liquid waste containing 10 co-existing cations (3 mol/L HNO3). This suggests that mesoporous silicas have great potential for Zr(IV) removal in actual radioactive liquids with high acidity during spent fuel reprocessing.