Column Adsorption Experiments Research Articles

Biomass polyamine-functionalized nanocellulose-loaded covalent organic framework to construct composite aerogels for highly efficient removal of Cr (VI) and methyl orange

Heavy metal ions and organic dyes cause ecological pollution, which is a problem that needs to be solved urgently. In this study, a novel biomass polyamine-functionalized nanocellulose loaded-covalent organic framework (COF) successfully constructed a hybrid aerogel (TDB). Due to the synergistic effect of biomass polyamines and COF, a vast number of active sites are present on the surface of TDB aerogel. This made the TDB aerogel have the largest adsorption capacity (470.67 mg/g, 488.22 mg/g) and the highest removal efficiency (98.49 %, 99.51 %) for Cr (VI) or MO (methyl orange). In the binary pollutant system, TDB aerogel also showed excellent removal efficiency for Cr (VI) and MO (91.29 %, 82.84 %). The adsorption process and adsorption mechanism of TDB aerogel were analyzed by adsorption kinetics, adsorption isotherms, thermodynamics, FTIR, and XPS. Its crystalline structure also didn't change. Fixed-bed column adsorption experiments showed that TDB aerogel could effectively purify 4510 mL of wastewater that contained Cr (VI) or 4681 mL of wastewater that contained MO. Therefore, TDB aerogel can be considered a promising adsorbent for the treatment of heavy metal ions and organic dyes in wastewater.

Removal of low concentration of perchlorate from natural water by quaternized chitosan sphere (CGQS): Efficiency and mechanism research

In this study, an innovative approach utilizing betaine as a raw material was employed to effectively modify the surface of chitosan with quaternary ammonium groups. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FTIR) characterization showed that the quaternary ammonium groups on betaine were successfully loaded on the chitosan surface. The effects of dosage, pH, initial perchlorate concentration, temperature and co-existing anions on the removal efficiency of perchlorate were investigated. The saturated adsorption capacity of CGQS was 35.41 mg/g under natural condition. The impact of initial perchlorate concentrations and column flow rates on the column adsorption experiments were investigated, as well as natural water tests. Sterilizing performance experiments of CGQS were carried out innovatively. Under the condition of initial concentration of 0.5 mg/L, 9 BV/h (bed volume per hour), the effluent natural water was up to standard (≤0.07 mg/L) with a treatment capacity of 210 BV/g, and the sterilizing rate of CGQS was up to 97.02%. The proposed adsorption mechanisms involved surface pore adsorption, electrostatic adsorption of quaternary ammonium groups, and ion exchange between chloride and perchlorate ions. The CGQS prepared in this work had great potential for treating trace perchlorate contamination in natural water.

Construction of 3D network aluminum sludge-based hydrogel beads: combination of macroization, amino functionalization, and resource utilization.

An aluminum sludge-based composite material was constructed against the problems of phosphorus pollution and the waste of aluminum sludge resources. Utilizing metal Ce doping and hydrogel microbeads with pore preparation, the adsorption performance of the original sludge was improved. Meanwhile, the macroscopic body was constructed, and on this basis, polyethyleneimine (PEI) was introduced to complete the amino functionalization further to enhance the adsorption of phosphorus by the adsorbent, and NH-CeAIS-10 microbeads were successfully prepared. In adsorption, microbeads with larger specific surface area and richer functional groups are better choice compared to original sludge. The results of SEM, BET, FT-IR, and XPS analyses indicate that the adsorption of phosphorus by the microbeads is mainly achieved through electrostatic interactions, ligand exchange, and the formation of inner-sphere complexes. According to the Langmuir model, the maximum phosphorus adsorption capacity of NH-CeAIS-10 was 29.56mgg-1, which was four times higher compared to native aluminum sludge. This also confirms the significant enhancement of phosphorus adsorption through the modification of aluminum sludge. Besides, in dynamic adsorption column experiments, the material exhibited up to 99% removal in simulated wastewater for up to 30days, demonstrating the great adsorption potential of NH-CeAIS-10 in engineering applications.

Dual-templating synthesis of superhydrophobic Fe3O4/PSt porous composites for highly efficient oil-water separation

Fe3O4/PSt porous composites with low density, interconnected network structure and superhydrophobic were prepared successfully by a dual-templating method, including High Internal Phase Emulsion (HIPEs) template method and the introduction of organic template species. It was worth mentioning that a novel amphiphilic di-block copolymers P(DMAEMA-b-St) were prepared as emulsifier by reversible addition fragmentation chain transfer (RAFT) polymerization method. At the same time, the effects of PS block length, emulsifier content, Fe3O4 content, DVB content and dispersed phase proportion on HIPEs droplet size and the corresponding polyHIPEs oil absorption were researched. The results showed that the oil adsorption capacity of 9.43 g/g toward toluene under optimal conditions. Subsequently, adsorption isotherm and adsorption kinetics were investigated. The results were shown that the adsorption of oil on adsorbent followed Freundlich model and pseudo-second-order (PSO) model. In addition, the adsorption experiments on a variety of oils demonstrated the wide applicability of Fe3O4/PSt porous composites. The cycling experiments proved that the Fe3O4/PSt porous composites had excellent cycling ability, were easy to recover and could be reused for multiple times. Finally, the adsorption column experiments showed that Fe3O4/PSt porous composites had powerful potential for industrial applications.

Transport of bisphenol A, bisphenol S, and three bisphenol F isomers in saturated soils.

With the limitation of the use of bisphenol A (BPA), the production of its substitutes, bisphenol S (BPS), and bisphenol F (4,4'-BPF) is increasing. Understanding the fate and transport of BPA and its substitutes in porous media can help reduce their risk of contaminating soil and groundwater systems. In this study, column and batch adsorption experiments were performed with 14C-labeled bisphenol analogs and combined with mathematical models to investigate the interaction of BPA, BPS, 4,4'-BPF, 2,2'-BPF, and 2,4'-BPF with four standard soils with different soil organic matter (SOM) contents. The results show that the transport capacity of BPS and 4,4'-BPF in the saturated soils is significantly stronger than that of BPA. Meanwhile, the mobility of the three isomers of bisphenol F exhibits variability in saturated soils with high SOM content. The two-site nonequilibrium sorption model was applied to simulate and interpret column experimental data, and model simulations described the interactions between the bisphenol analogs and soil very well. The fitting results underscore SOM's role in providing dynamic adsorption sites for bisphenol analogs. Hydrophobicity primarily accounts for the disparity in adsorption affinity between BPA, BPS, 4,4'-BPF, and soil, whereas hydrogen bonding forces may predominantly influence the differential adsorption affinity between 4,4'-BPF and its isomers and soil. The results of this study indicate that BPS and three isomers of BPF, as alternatives to BPA, have higher mobility in saturated soils and may pose a substantial risk to groundwater quality. This study enhances our understanding of bisphenol analogs' behavior in natural soils, facilitating an assessment of their environmental implications, particularly regarding groundwater contamination.

More movement with manure: increased mobility of erythromycin through agricultural soil in the presence of manure.

Antibiotic residues in the environment threaten soil and aquatic organisms and human and livestock health through the building of antimicrobial resistance. Manure spreading associated with animal agriculture is one source of environmental antibiotic residues. To better understand the risk of contamination, we studied the adsorption of erythromycin, a model macrolide antibiotic used across human and animal medicine. We conducted a series of equilibrium batch experiments to determine the kinetics and extent of adsorption and a continuous-flow column adsorption experiment to observe non-equilibrium adsorption patterns. We determined that the adsorption equilibration time to soil was approximately 72 h in our batch experiments. Erythromycin adsorbed to soil relatively strongly (K = 8.01 × 10-2 L/mg; qmax = 1.53 × 10-3 mg/mg), adsorbed to the soil in the presence of manure with less affinity (K = 1.99 × 10-4 L/mg) at a soil: manure ratio of 10:1 by mass, and did not adsorb to manure across the solid ratios tested. We observed multi-phased adsorption of erythromycin to the soil during the non-equilibrium column experiment, which was largely absent from the treatments with both soil and manure present. These results suggest that erythromycin is more mobile in the environment when introduced with manure, which is likely the largest source of agriculturally sourced environmental antibiotics.

Self-cross-linking of metal-organic framework (MOF-801) in nanocellulose aerogel for efficient adsorption of Cr (VI) in water

Chromium (Cr) poses significant hazards to both human health and the natural environment. Therefore, in this study, metal-organic framework (MOF-801) was compounded with nanocellulose aerogel for the first time. And a nanocellulose/metal-organic framework composite aerogel was developed for efficient chromium ion adsorption. The resulting aerogel has an ultra-low density (0.017 g/cm3) and high porosity (98.87%). The removal efficiency of this aerogel for Cr (VI) (93.86%) was measured to be higher than that of cellulose nanofiber aerogel (TCNF: 50.08%) and MOF-801 powder (59.86%). It was also higher than the cellulose nanocellulose aerogel prepared without MOF-801 (TMPA: 70.58%). This is because MOF-801 cross-linked with nanocellulose increased its porosity and provided a large number of adsorption sites. The maximum adsorption of Cr (VI) by this aerogel was 350.64 mg/g (5.96 mg/cm3). The adsorption mechanism was investigated by adsorption isotherms, adsorption kinetics, XPS, and FT-IR analysis. The aerogel has good reusability, with no significant loss of adsorption performance over 6 cycles. It is worth mentioning that 0.69 g (V: 7.363 cm3) of aerogel could effectively remediate 3710 mL of chromium-containing wastewater in a fixed-bed column adsorption experiment. In addition, the aerogel can effectively remove many metal ions from wastewater. As a result, the aerogel made in this study has the ability to be an effective adsorbent for metal ion removal.

Alumina microspheres for the adsorption of fatty alcohols containing oxygenates in Fischer-Tropsch synthetic oils

The efficient and economical removal of oxygenated compounds from Fischer-Tropsch synthetic oil is vital to the promotion of high-quality chemical development in the coal chemical industry. In this study, alumina microspheres with high specific surface area, high pore capacity, and small particle size were prepared. The adsorption thermodynamics, adsorption kinetics, and column adsorption experiments were systematically conducted on various fatty alcohols bearing different carbon numbers, in mixtures of α-olefins and alkanes with different carbon numbers. The competitive adsorption behavior between weakly polar, oxide-containing methyl acetate and 12-alcohols on an alumina surface was investigated to better reduce the actual system. The Freundlich model exhibited a better fit than the Langmuir model. The adsorption kinetics and proposed first-order kinetic equations fitted better to the Crank model. Comparing the adsorption effect of commercial alumina and the alumina microspheres prepared in this study, it was observed that a smaller particle size and larger pore volume reduced the internal and external diffusion resistance of adsorption, and a larger specific surface area provided more adsorption sites for the adsorption of the oxide-containing compounds. The competitive adsorption behavior of fatty alcohols and methyl acetate on the surface of γ-alumina was explored using a combination of density functional theory (DFT) calculations and experimental techniques. The results of this study can prove to be extremely useful for the efficient removal of oxide-containing compounds from Fischer-Tropsch synthetic oils.

Synergistic effects of tungstate trioxide hemihydrate decorated reduced graphene oxide for the adsorption of heavy metals and dyes and postliminary application in supercapacitor device

Simultaneously managing water pollution, energy crises, and adherence to green chemistry standards poses a significant challenge. The objective of this investigation is to synthesize a novel material suitable for adsorbing contaminants that are typically found in wastewater, and to suggest an alternative approach for managing the spent adsorbent. A tungstate trioxide hemihydrate (WO30.5H2O) decorated reduced graphene oxide (RGO) nanocomposite (RGO-WO30.5H2O NCs) was synthesized and their batch and continuous operation for the removal of heavy metal ions and dyes from synthetic wastewater was investigated. The RGO-WO30.5H2O NCs presented batch adsorption capacity (removal percentage) of 28.005 mg/g (93.35%), 26.985 mg/g (89.95%), 25.935 mg/g (86.45%), 242.69 mg/g (97.07%), 186.97 mg/g (93.48%) for Pb2+, Cd2+, Ni2+, MB and CV, respectively. The fixed-bed column adsorption experiments presented the adsorption amount in between 123 and 79 mg/g for MB and 93 to 71 mg/g for CV as the concentration varied from 100 to 50 mg/L and 52 to 30 mg/g for Pb2+, 45 to 28 mg/g for Cd2+, and 36 to 25 mg/g for Ni2+, as the concentration varied from 50 to 20 mg/L and the breakthrough curves were fitted by the Yoon-Nelson and Thomas models. After then, the spent adsorbent was repurposed for energy storage based on the “waste-to-wealth" principle to prevent secondary pollution. The nanomaterial based on WO30.5H2O NPs, RGO-WO30.5H2O NCs, Ni(II)-Adsorbed RGO-WO30.5H2O exhibited specific capacitance of 306.42, 276.96, and 241.06 F/g, respectively, at 1.25 A/g. The Ni(II)-Adsorbed RGO-WO30.5H2O showed almost comparable capacitance stability of 75% with RGO-WO30.5H2O NCs (82%) after 12000 cycles in 1 M Na2SO4. The fabricated Ni(II)-Adsorbed RGO-WO30.5H2O-based symmetric supercapacitor device displayed energy density of 47.77 Wh/kg at power density of 45 kW/kg while exhibiting specific capacitance of 90% after 10,000 cycles. This research presents a novel methodology for the utilization of spent-adsorbent in energy storage applications, showcasing a significant environmental impact towards reducing the waste generated by conventional adsorption method.

A comparative study of experimental and advanced modelling analysis for adsorption of Cd (II) from aqueous solution by Melia azedarach L. charcoal powder

The present study deals with the preparation and characterization of Melia azedarach L. twigs charcoal powder (MAT-CP) followed by batch and column adsorption experiments to appraise its Cd(II) removal efficiency from aqueous solution. The characterization of charcoal was done using XRD, FTIR, FESEM, EDX and BET analysis. Batch adsorption study was conducted with varied variables including adsorbent dose, contact time, temperature, pH and agitation speed. Resultant data was suitably fitted in Langmuir isotherm model exhibiting a maximum 196.078 mg/g adsorption capacity. Kinetic studies revealed that the adsorption followed Pseudo-second order kinetic while thermodynamic analysis (enthalpy (ΔH°), entropy (ΔS°) and Gibb’s free energy (ΔG°)) revealed the interaction to be thermodynamically favorable and endothermic. Regeneration of adsorbent was also done and the reactivated MAT-CP was repeatedly used as adsorbent. In fixed-bed column investigation, variables such as flow rate, initial metal concentration and column bed height were varied to obtain breakthrough curves (BTCs). The column adsorption was optimally obtained at 2.5 mL/min flow rate, 25 mg/L of Cd(II) concentration and 5 cm bed height. Column adsorption modeling reflected higher R2 and adsorption capacity using Thomas and Nelson-Yoon models. The present study advocates the MAT-CP as an efficient adsorbent for Cd(II) removal from aqueous solution.

Preparation and application of porous functional polymers for boron removal in seawater desalination by a mild and free-organic solvents process

The development of high-performance adsorbents to address high concentrations of boron and thus acquirement of drinkable water from seawater is a huge challenge. Most of the boron removal adsorbents reported in the literature have complex and organic solvents involved in preparation processes, which makes industrial production difficult. Herein, the porous cross-linked polyglycidyl methacrylate (CLPGMA) with a rich pore structure is prepared in one step by water-in-oil high internal phase emulsification, and then functionalized using water as a solvent to dissolve glucosamine to obtain the boron removal adsorbent. The whole preparation process is facile and free-organic solvents, making it suitable for further industrial production. The adsorbent demonstrates excellent performance in batch adsorption. Especially, we propose to combine the adsorption with reverse osmosis technology, by which the drinkable desalinated seawater can be obtained. The column adsorption experiments show that the adsorbent can rapidly remove boron from desalinated seawater at high flow rates under dynamic conditions to meet drinking water standards. This research provides a new method for the green large-scale synthesis of high-performance boron adsorbent for seawater desalination.

Highly effective recovery of palladium from a spent catalyst by an acid- and oxidation-resistant electrospun fibers as a sorbent

Palladium is not only a precious metal but also is widely used in catalyst production, therefore it is of significance to recover palladium from spent catalysts. In this paper, Nanofiber modified by 2-Thionicotinic acid (TN-Nanofiber) featuring acid- and oxidation-resistant was fabricated through electrospinning and chemical grafting, which can trap efficiently Pd(II) ions from the extremely acidic and oxidizing systems derived from the leaching of spent catalyst. The adsorption kinetic data of Pd(II) ions was well described by the pseudo-second-order model, and the times required to reach equilibrium was 60 min. The Langmuir isotherm model provided better fitting for the Pd(II) ions adsorption, and the maximum uptake capacity of TN-Nanofiber was evaluated as 348.4 mg/g for Pd(II) ions. Furthermore, the column adsorption experiments proved the feasibility of TN-Nanofiber separation of Pd(II) ions from the spent catalyst. Investigation of the adsorption mechanism demonstrated a planar quadrilateral coordination pattern between the Pd(II) ions and the adsorption sites of TN-Nanofiber, which includes one N and one S atom sourced from the adsorption sites and two Cl atoms derived from the original PdCl42−. In summary, TN-Nanofiber may serve as the next generation of emerging adsorbents to recover palladium from the strongly acidic and oxidizing systems due to its excellent performance.

Qualitative and quantitative analysis for Cd2+ removal mechanisms by biochar composites from co-pyrolysis of corn straw and fly ash

Removal of heavy metals (e.g., Cd) from contaminated water using waste-converted adsorbents is promising, but the efficiency still needs to be improved. Here, we prepared a functional biochar composite as novel Cd adsorbents by co-pyrolysis of two typical solid wastes, i.e., agricultural corn straw and industrial fly ash. The adsorption behavior and mechanism were investigated using batch and column adsorption experiments and modern characterization techniques. Results showed that alkali-modified fly ash (AMFA) was loaded onto the surface of the corn straw biochar as some fine particle forms, with quartz (SiO2) and silicate being the main mineral phases on the surface. The maximum sorption capacity fitted by Langmuir model for functionalized biochar composite (FBC700) was up to 137.1 mg g−1, which was 7.7 times higher than that of the original corn straw biochar (BC700). Spectroscopic analysis revealed that adsorption mechanisms of Cd onto the FBC700 included mainly precipitation and ion exchange, with complexation and Cd-π interaction also contributing. The AMFA could effectively improve the mineral precipitation with Cd. The adsorption columns filled with FBC700 exhibited a longer breakthrough time than that filled with BC700. The adsorption capacity calculated by Thomas model for FBC700 was also approximately 6.0 times higher than that for BC700, showing that FBC700 was more suited to practical applications. This study provided a novel perspective for recycling solid wastes and treating Cd-contaminated water.

Removal Performance and Mechanism of Emerging Pollutant Chloroquine Phosphate from Water by Iron and Magnesium Co-Modified Rape Straw Biochar.

Chloroquine phosphate (CQP) is effective in treating coronavirus disease 2019 (COVID-19); thus, its usage is rapidly increasing, which may pose a potential hazard to the environment and living organisms. However, there are limited findings on the removal of CQP in water. Herein, iron and magnesium co-modified rape straw biochar (Fe/Mg-RSB) was prepared to remove CQP from the aqueous solution. The results showed that Fe and Mg co-modification enhanced the adsorption efficiency of rape straw biochar (RSB) for CQP with the maximum adsorption capacity of 42.93 mg/g (at 308 K), which was about two times higher than that of RSB. The adsorption kinetics and isotherms analysis, as well as the physicochemical characterization analysis, demonstrated that the adsorption of CQP onto Fe/Mg-RSB was caused by the synergistic effect of pore filling, π-π interaction, hydrogen bonding, surface complexation, and electrostatic interaction. In addition, although solution pH and ionic strength affected the adsorption performance of CQP, Fe/Mg-RSB still had a high adsorption capability for CQP. Column adsorption experiments revealed that the Yoon-Nelson model better described the dynamic adsorption behavior of Fe/Mg-RSB. Furthermore, Fe/Mg-RSB had the potential for repeated use. Therefore, Fe and Mg co-modified biochar could be used for the remediation of CQP from contaminated water.

As(III) removal by a recyclable granular adsorbent through dopping Fe-Mn binary oxides into graphene oxide chitosan

Graphene oxide chitosan composite (GOCS) is recognized as an environmentally friendly composite adsorbent because of its stability and abundant functional groups to adsorb heavy metals, and Fe-Mn binary oxides (FMBO) have attracted increasing interest due to their high removal capacity of As(III). However, GOCS is often inefficient for heavy metal adsorption and FMBO suffers poor regeneration for As(III) removal. In this study, we have proposed a method of dopping FMBO into GOCS to obtain a recyclable granular adsorbent (Fe/MnGOCS) for achieving As(III) removal from aqueous solutions. Characterization of BET, SEM-EDS, XRD, FTIR, and XPS are carried out to confirm the formation of Fe/MnGOCS and As(III) removal mechanism. Batch experiments are conducted to investigate the effects of operational factors (pH, dosage, coexisting ions, etc.), as well as kinetic, isothermal, and thermodynamic processes. Results show that the removal efficiency (Re) of As(III) by Fe/MnGOCS is about 96 %, which is much higher than those of FeGOCS (66 %), MnGOCS (42 %), and GOCS (8 %), and it increases slightly with the increasing molar ratio of Mn and Fe. This is because amorphous Fe (hydro)oxides (mainly in the form of ferrihydrite) complexation with As(III) is the major mechanism to remove As(III) from aqueous solutions, and it is accompanied by As(III) oxidation mediated by Mn oxides and the complexation of As(III) with oxygen-containing functional groups of GOCS. Charge interaction plays a weaker role in As(III) adsorption, therefore Re is persistently high over a wide range of pH values of 3–10. But the coexisting PO43− can greatly decrease Re by 24.11 %. As(III) adsorption on Fe/MnGOCS is endothermic and its kinetic process is controlled by pseudo-second-order with a determination coefficient of 0.95. Fitted by the Langmuir isotherm, the maximum adsorption capacity is 108.89 mg/g at 25 °C. After four times regeneration, there is only a slight decrease of <10 % for the Re value. Column adsorption experiments show that Fe/MnGOCS can effectively reduce As(III) concentration from 10 mg/L to <10 μg/L. This study provides new insights into binary polymer composite modified by binary metal oxides to efficiently remove heavy metals from aquatic environments.

A novel S,N-rich MOF for efficient recovery of Au(III): Performance and mechanism

A novel S,N-rich MOF with adenine and 4,4′-thiodiphenol as organic ligands was synthesized via the one-step solvothermal method, and used for gold recovery. The pH impact, adsorption kinetics, isotherms, thermodynamics, selectivity, and reusability were investigated accordingly. The adsorption and desorption mechanism were also explored comprehensively. The electronic attraction, coordination, and in situ redox account for the Au(III) adsorption. The Au(III) adsorption is affected strongly by the pH of solutions, and best at pH of 2.57. The MOF exhibits exceptional adsorption capacity as high as 3680 mg/g at 55 °C, fast kinetics with 8 min for 9.6 mg/L Au(III), and excellent selectivity for gold ion in real e-waste leachates. The adsorption process of gold on the adsorbent is endothermic and spontaneous, and influenced visibly by temperature. The adsorption ratio still maintained 99% after seven adsorption-desorption cycles. The column adsorption experiments show that the MOF has outstanding selectivity for Au(III) with 100% of removal efficiency in a complex solution containing Au, Ni, Cu, Cd, Co, and Zn ions. A glorious adsorption with a breakthrough time of 532 mins was obtained for the breakthrough curve. This study not only provides an efficient adsorbent for gold recovery, but also guidance for designing new materials.

Multifunctional pH-responsive carbon-based hydrogel adsorbent for ultrahigh capture of anionic and cationic dyes in wastewater

An environmental friendly hydrogel adsorbent (DEC@GEL) was successfully manufactured by a facile free-radical polymerization method. Multiple characterizations demonstrated that the adsorbent was rich in functional groups and porous structures. The batch and multisystem adsorption experiments were applied to systematically investigate the adsorption properties of methylene blue (MB), malachite green (MG), indigo sodium dimethyl sulfonate (IC) and tartrazine (TR) in wastewater. The experimental results proved that the kinetic and isotherms of four dyes were more consistent with the pseudo-second-order and Langmuir model, respectively. Notably, the maximum adsorption capacities of MB, MG, TR and IC at 318 K were 2186.85, 2302.53, 1766.13 and 2301.75 mg/g, respectively, which were higher than many adsorbents that had been reported. Recycle experiment demonstrated the high reusability of the DEC@GEL. The selectivity and adsorption column experiments proved that DEC@GEL was not only widely applicable to various dyes, but also provided a positive start for the industrial application. Moreover, the simulated adsorption experiments further demonstrate that DEC@GEL had the prospect of application in real industrial conditions. Finally, four adsorption mechanisms had been proposed. Various adsorption experiments had shown that DEC@GEL was not only efficient in processing dyes, but also had great potential for practical industrial applications.

Removal of PFAS from groundwater using weak‐base anion exchange resins

AbstractThis research provides new insights on the application of weak‐base (WB) anion exchange resins (AERs) for groundwater treatment of six perfluoroalkyl acids (PFAAs) with different properties. Continuous‐flow column adsorption and regeneration experiments involving WB, polyacrylic, and WB, polystyrene resins were conducted considering salt‐only regeneration solutions and two representative strong‐base (SB)‐AERs of analogous polymer composition and a third solution of methanol/salt used as baseline for comparison. The WB, polyacrylic resin was regenerated using salt‐only solutions of NaOH due to deprotonation of the tertiary amine functional group at alkaline pH. However, organic cosolvent was required to weaken the hydrophobic interactions between PFAAs and the nonpolar WB, polystyrene resin. Removal was predominantly influenced by polymer composition with free‐base WB‐AERs exhibiting similar selectivity and higher capacity as SB resin counterparts. This work highlights WB‐AER selection based on PFAA‐selective removal and more sustainable regeneration strategies.

Adsorption Characteristics of Phosphate Based on Al-Doped Waste Ceramsite: Batch and Column Experiments.

Phosphorus widely existing in rainfall and wastewater impacts the water environment. In this study, sludge, cement block, and coal fly ash were employed as ceramsite material to synthesize Al-doped waste ceramsite (Al-ceramsite) for removing phosphate (PO43--P) from aqueous solutions. Batch static adsorption-desorption experiments were designed to investigate the effect of various parameters such as Al-ceramsite dosage, PO43--P concentration, temperature, initial pH, coexisting ions, and desorbents on the removal of PO43--P. Also, the fate of PO43--P removal efficiency in actual rainwater was studied through dynamic adsorption column experiments using Al-ceramsite. Results showed that Al-ceramsite could remove PO43--P efficiently under the optimum parameters as follows: Al-ceramsite dosage of 40 g/L, initial PO43--P concentration of 10 mg/L, temperature of 25 °C, and pH of 5. Besides that, the Al-ceramsite could completely remove PO43--P in actual rainwater, and the effluent PO43--P concentration was lower than the environmental quality standards for surface water Class Ⅰ (0.02 mg/L). The adsorption characteristics of Al-ceramsite on PO43--P by X-ray photoelectron spectroscopy (XPS) were further explained. As a result, ligand exchange and complexation were confirmed as the main PO43--P removal mechanism of Al-ceramsite. Thus, Al-ceramsite was prepared from industrial waste and has shown excellent potential for phosphorus removal in practical applications.

Treatment of raw sanitary landfill leachate using a hybrid pilot-scale system comprising adsorption, electrocoagulation and biological process

The effectiveness of a three-stage pilot approach using adsorption (AD), electrocoagulation (EC) and biological (BIO) processes for the treatment of raw sanitary landfill leachate (SLL) was investigated. SLL is loaded with hazardous substances such as organic load and heavy metals with high ammonium nitrogen (NH4+-N) concentrations and is also produced in large quantities, causing serious risks to both living organisms and the environment. In this study, column adsorption experiments were initially performed to examine the removal of toxic NH4+-N using different initial NH4+-N concentrations and recirculation flow rates. The adsorption process was then examined as a pre-treatment step in two sequential treatment scenarios, i.e., AD-EC-BIO and AD-BIO-EC, to determine which achieved the highest removal of pollutants and leachate toxic potential, thus ensuring the biosafety of these processes during the release of the respective effluents into surface waters. The overall removal efficiencies of NH4+-N, color, dissolved chemical oxygen demand (d-COD), manganese (Mn), nickel (Ni), zinc (Zn) and iron (Fe) achieved after the application of the AD-EC-BIO system were 95.5 ± 0.1%, 98.8 ± 0.1%, 85.7 ± 0.8%, 100 ± 0.1%, 71.4 ± 1.7%, 63.8 ± 1.9% and 94.2 ± 0.2%, respectively, while the values for the AD-BIO-EC system were 98.5 ± 0.2%, 98.7 ± 0.1%, 85.7 ± 0.4%, 98.9 ± 1.2%, 67.7 ± 1.7%, 76.1 ± 1.6% and 94.8 ± 0.1%, respectively. In accordance with the latter, the assessment of leachate toxic potential using a Thamnocephalus platyurus bioassay revealed that the AD-EC-BIO system could be considered a promising treatment strategy for the purification of raw SLL.