Efficient Co-removal Research Articles

Efficient co-removal of aqueous Cr(VI) and ciprofloxacin by alkali lignin-derived carbon supported nanoscale zero-valent iron via adsorption and redox synergistic mechanisms

Developing an efficient co-removal strategy is crucial for the treatment of combined contaminants with heavy metals and antibiotics due to their great threat to sustainable advancement and ecological preservation. Herein, the efficient co-removal of aqueous hexavalent chromium (Cr(VI)) and ciprofloxacin (CIP) is achieved via a newly developed composite of nanoscale zero-valent iron particles embedded into alkali lignin-derived carbon (nZVI/ALC) without external assistance (such as light, advanced oxidants). nZVl/ALC demonstrates superior co-removal efficiencies of Cr(VI) (99.9 %) and CIP (89.9 %) with high removal kinetic rate constants of 1.595 and 0.779 min−1, respectively. The underlying mechanisms involving the co-removal of Cr(VI) and CIP verify that Cr(VI) ions are adsorbed onto the skeleton of nZVI/ALC originating from the electrostatic interaction, and CIP molecules adsorbed on nZVl/ALC act as a bridge, complexing with the Cr(VI) ions to promote Cr(VI) removal. Meanwhile, the CIP adsorption by nZVI/ALC involves hydrogen bonding, π-π interaction, and complexation. The coexisting Cr(VI) ions are transformed into Cr(III) components with abundant electron transfer, leading to the generation of more •O2– radicals, thus the self-generating reactive oxygen species (•OH, •O2– and 1O2) in ambient-air condition promote CIP degradation in the binary system. The CIP molecules’ degradation pathways mainly include piperazine ring cracking, piperazine epoxidation, quinolone ring opening and defluorination according to the analysis of HPLC-MS and FuKui function, along with the gradual reduction in toxicity throughout the degradation process of CIP molecules. This study offers a new insight on the co-removal of Cr(VI) and CIP, which would provide promising guidance for the remediation of compound wastewater with heavy metals and antibiotics.

Zwitterionic adsorbents derived from self-Exfoliated ionic covalent organic frameworks for efficient Co-Removal of anionic and cationic radionuclides

Exfoliating Covalent Organic Frameworks (COFs) into few-layer or even monolayer nanosheets not only improves the exposure of active sites and facilitates mass transfer efficiency, but also enhances their solubility or dispersion to achieve solution processability. As the Coulomb repulsion can weaken the stacking interactions, the construction of ionic COFs shows promising prospects for obtaining self-stripping nanosheets, but precisely controlling the self-exfoliated degree remains a challenge. Herein, we found for the first time that varying the number of hydroxyl groups in the building blocks could significantly affect the self-exfoliated degree for ionic COFs, and thus successfully produced a series of ionic COFs with stepwise solubility differences. Interestingly, the trend of self-exfoliated degree and solubility of cationic (EBCOFs) and anionic COFs (SDCOFs) were completely opposite to each other. Mechanistic studies indicated that more hydroxyl groups as electron donating groups increased the electron density of ionic COFs, resulting in a decrease in the Coulomb repulsion of cationic COFs (EBCOFs) but an increase in the Coulomb repulsion of anionic COFs (SDCOFs). Furthermore, in order to achieve the efficient co-removal of anionic and cationic radionuclides, we assembled cationic and anionic COF nanosheets through electrostatic attraction to obtain a novel zwitterionic COF (EB@SD COF) with both anion and cation adsorption sites. Impressively, EB@SD COF demonstrated rapid and efficient co-adsorption of ReO4- (a substitute for TcO4-) and Sr2+ with the maximum adsorption capacities of 117.6 and 122.4 mg/g, respectively. This work not only developed an effective zwitterionic COF adsorbent for the co-removal of radionuclides but also broadened the horizon of preparation methods for self-exfoliated ionic COFs.

Efficiency and synergy of MnO2@LDO for arsenic and fluoride simultaneous sorption from water

High levels of groundwater containing both arsenic and fluorine are prevalent, resulting in serious health problems when consumed as drinking water. This co-pollution phenomenon is widespread and requires urgent attention. The multiple forms of arsenic and arsenic–fluorine co-contamination pose a significant challenge to efficiently co-remove both substances. This research utilized a green and stable synthesis approach to create MgLaFe layered double oxide (LDO) heterostructures, which were anchored on α-MnO2 nanowires. The materials comprise magnesium and lanthanum elements with a powerful attraction toward fluoride ions; elemental iron, which can establish stable compounds with arsenate; and MnO2, which can effectively oxidize arsenous acid, thereby enabling efficient co-removal of arsenic and fluorine. The efficient oxidation process of the MnO2 nanowire and the prompt ion adsorption process of the LDO work together synergistically. The adsorption performance was assessed through isotherms and kinetic fitting. Chemisorption was found to be the process for As(Ⅲ), As(V), and F− adsorption, with As(Ⅲ) going through monolayer adsorption on the surface of MnO2 nanowires, while As(V) and F− were mainly adsorbed by multilayer process on LDO. The maximum adsorption capacities were 111.76, 230.51, and 765.10 mg/g for As(Ⅲ), As(V), and F−, respectively. The x-ray photo-electronic spectroscopy analysis provided further elucidation on the adsorption mechanism of the MnO2@LDO heterostructure, detailing each component's role in the process. The results confirm the successful construction of the heterostructure and the efficient coupling of oxidation and adsorption.

Simultaneous abatement of NOx and CO using tandem catalyst system via reactant- and energy- Co-promoting effect

Although selective catalytic reduction (SCR) of NOx with NH3, CO catalytic oxidation, and selective catalytic reduction of NOx with CO have been used to control NOx and CO from mobile and industrial sources, the simultaneous removal of NOx and CO at low temperatures remains a great challenge due to the specificity of each catalytic reaction. Here, we achieve the simultaneous abatement of NOx and CO at low temperatures by skillfully utilizing a tandem catalyst system (e.g., Cu1/MnO2 and Ce-W/TiO2 as oxidation-SCR tandem catalysts). Through a series of catalytic activity evaluations and structural characterizations, we report that NO can promote the oxidation of CO due to the easier decomposition of the intermediates formed by the combination of adsorbed NO species and gaseous CO, and the faster supply of O* required for CO oxidation in CO+O2+NO2/NO atmosphere. Meanwhile, the heat released from the oxidation of CO not only accelerates the oxidation of NO in the oxidation system, but also contributes to the high reaction rate of subsequent fast NH3-SCR. Eventually, 100 % conversion of CO and 80 % conversion of NO appear at 128 and 186 °C, respectively. This work provides a new strategy for the simultaneous and efficient removal of CO and NOx at lower temperatures.

Synthesis of MgLaFe MMO Composites and Their Adsorption Properties for Co-removal of Fluoride and Arsenic from Water

Fluorine and arsenic co-contamination in groundwater is a common phenomenon in Northwest China, leading to serious health problems when consumed as drinking water due to high levels of both contaminants. It is important to note that the region's highly fluoridated and arsenic groundwater is widely distributed. Achieving efficient adsorption and co-removal of these pollutants is particularly challenging due to their co-pollution and strict drinking water standards. The study achieved the preparation of Mg-La-Fe mixed metal oxide composites through a green and stable synthesis pathway. The composites consist of magnesium and lanthanum hydroxides with a strong affinity for fluoride ions and iron, which can form stable compounds for arsenate and arsenite, enabling efficient co-removal of fluoride and arsenic ions. The material can adsorb up to 30.26 mg∙g-1, 36.96 mg∙g-1, and 133.65 mg∙g-1 of As(III), As(V), and F-, respectively, in solution. Even after four cycles, the adsorption of As(III), As(V), and F- remains at 81.11%, 81.36%, and 80.87%, respectively. This study obtained an efficient adsorption material for the co-removal of fluorine and arsenic, providing a theoretical basis and technical support for ensuring the safety of drinking water in remote areas of Northwest China.

Effect of Co3O4 powder on the explosion characteristics and CO products of methane-air mixture

Rapid removing toxic CO for methane-air mixture explosions is essential in reducing casualties, but relevant research is rare. This paper proposed a novel approach for efficient CO removal and explosion suppression for methane-air mixture explosions using Co3O4 powder. The effect of Co3O4 powder on the explosion characteristics and basic parameters to quantify the CO removal performance have been studied, mainly including maximum explosion pressure (Pm), combustion time (tc), flame propagation velocity, and average CO removal rate (Rave.). Results indicated that explosion intensity and CO concentration decreased significantly with Co3O4 powder, due to increased heat absorption capacity and the active site of CO catalytic oxidation. However, the average CO removal rate decreased as the Co3O4 powder usage and CH4 partial pressure increased, which could reduce the dispersion degree of the Co3O4 dust cloud. The CO removal was achieved through the CH4 catalytic combustion and CO catalytic oxidation, which could reduce the CO generation and oxidize the generated CO to harmless CO2, respectively. This work provides a novel routine to lessen the explosion hazards and has promising applications in emergency rescue.

Synergistic removal of NOx and CB by Co-MnOx catalysts in a low-temperature window

The simultaneous removal of NOx and CVOCs in a deNOx unit has gained significant attention in recent years. However, efficient co-removal of NOx and CVOCs is still a challenge due to the low tail gas emission temperatures in the non-electric industry. To address this, m-MnOx (m = Sn or Co) catalysts were prepared based on the Mn-based catalyst to investigate their catalytic performance in removing NOx and CB.The results demonstrated that the Co-MnOx catalyst exhibited the best catalytic activity, achieving over 90 % NOx conversion within the temperature window of 105–275 °C, while CB conversion rates surpassed 90 % above 180 °C. The characterization results revealed that Co doping formed MnCo2O4 adding additional Lewis acid sites and promoted the conversion of Mn2+ to Mn3+ and Mn4+, thereby improving the redox ability and surface acidity of the Co-MnOx catalyst. DFT simulations revealed that Co addition improved the adsorption of NH3 and CB on the Co-MnOx catalyst and effectively reduced the energy barriers for N-H cleavage and oxygen vacancy formation. This work is hoped to provide an important reference for the further design and optimization of efficient low-temperature NOx/CB synergistic removal catalysts.

Insights into the underpinning effect of graphene in Cu1Mn10 on enhancing the low-temperature catalytic activity for CO oxidation

CO emission is a critical issue of industrial processes such as steel-smelting, cement manufacturing, and waste incineration. Catalytic oxidation based on Cu–Mn binary catalysts shows great potential for efficient removal of CO, whereas their practical applicability is limited by the inferior low-temperature catalytic activity and the high catalyst cost owing to a substantial quantity of Cu. In this study, doping graphene is designed to adjust the electron transfer capability to improve the low-temperature catalytic activity as well as reduce the amount of Cu, and thereby Cu1Mn10 catalysts doped with slight amounts of graphene (x%G-Cu1Mn10, x is 1∼5) were fabricated. It was found that the introduction of graphene could form effective electron transport channels to enhance the intermetallic interaction and oxygen vacancy generation, thus improving the low-temperature catalytic performance of the Cu1Mn10 catalyst. Among all the catalysts, 4%G-Cu1Mn10 exhibited the highest activity, achieving CO conversion of 92% at 110 °C at a weight hourly space velocity of 120,000 mL/(g∙h). The introduction of graphene also enabled the catalyst with excellent catalytic activity and stability at a relative humidity of 70%. Attractively, 4%G-Cu1Mn10 can be further loaded into the polyester fabric, presenting great application potentials in the effective elimination of CO during the dust removal process since the flue gas temperature in the dust collector is just around the T90% and the catalyst that is inside of fabric fiber rather than on the fabric surface can be rarely influenced by the dust. In general, doping graphene provides a facile method to enhance the low-temperature activities of the Cu–Mn binary catalysts and cut down the use of valuable Cu, showing great application potential.

Efficient removal of Co(II) from aqueous solution by one-step preparation of heterocyclic ligand-functionalized MOFs: study on adsorption properties and irradiation stability

Efficient removal of Co(II) from aqueous solution by one-step preparation of heterocyclic ligand-functionalized MOFs: study on adsorption properties and irradiation stability

Support Effect and Stability of Inverse Fe1(OH)x/Pt Single-Site Interfacial Structured Catalysts for Preferential CO Oxidation in H2

Preferential oxidation of CO in hydrogen (PROX) has been regarded as a promising method for removing a trace amount of CO to a parts-per-million (ppm) level to provide pure hydrogen fuel for polymer-electrolyte membrane fuel cells. Recently, we reported that SiO2-supported Pt nanoparticles with atomically dispersed Fe1(OH)x decoration exhibited exceptional CO removal in a very broad temperature window of −75–107 °C in the PROX reaction because of enriched interfaces and remarkably high reducibility of the iron species. Here, we further investigated the support effect on the catalytic performance of this inverse Fe1(OH)x/Pt single-site interfacial structure, as well as their stabilities under high-temperature redox atmospheres. We found that Fe1(OH)x/Pt on nonreducible supports such as SiO2 and Al2O3 is more favorable for efficient CO removal than those on reducible supports (e.g., Fe2O3 and TiO2) in the PROX reaction. The inferior performance of the latter case is attributed to the creation of additional active interfaces to initiate competing H2 oxidation. High-temperature redox pretreatments of the optimized SiO2-supported Fe1(OH)x/Pt catalyst up to 500 °C did not cause any noticeable changes of the temperature window of complete CO removal, indicating that the inverse Fe1(OH)x/Pt single-site interface structure has high thermal stability against sintering. Further increasing the H2 concentration did not change the temperature window either. The above results suggest that the inverse Fe1(OH)x/Pt catalyst is very robust with high potential for practical applications and other catalytic reactions.

The interaction between Pseudomonas C27 and Thiobacillus denitrificans in the integrated autotrophic and heterotrophic denitrification process

Compared to autotrophic and heterotrophic denitrification process, the integrated autotrophic and heterotrophic denitrification (IAHD) shows wider foreground of applications in the actual wastewaters with organic carbon, nitrogen and sulfur co-existing. The efficient co-removal of sulfur, nitrogen, and carbon in the IAHD system is guaranteed by the interaction between heterotrophic and autotrophic denitrificans. In order to further explore the interaction between functional bacteria, Pseudomonas C27 and Thiobacillus denitrifcans were selected as typical heterotrophic and autotrophic bacteria, and their characteristics metabolic responses to different sulfide concentrations were studied. Pseudomonas C27 had higher metabolic activity than T. denitrificans in the IAHD medium with sulfide concentration of 3.12–15.62 mmol/L. Moreover, the fastest sulfide removal rate (0.35 mmol/L·h) was achieved with a single inoculation of Pseudomonas C27. Meanwhile, in mixed inoculant conditions, the interaction between Pseudomonas C27 and T. denitrificans (P:T = 3:1, P:T = 1:1 and P:T = 1:3) yielded the highest sulfide removal efficiency (more than 85%) when sulfide concentration was 6.25–12.5 mmol/L. Additionally, the sulfide removal rate increased with the inoculation proportion of Pseudomonas C27. Thus, this apparent interaction provided a theoretical basis for further understanding and guidance on the efficient operation of IAHD system.

Application of Nanosized Zeolite X Modified with Glutamic Acid as a Novel Composite for the Efficient Removal of Co(II) ions from Aqueous Media

In this work, nanosized zeolite X modified with glutamic acid was facilely synthesized as a novel composite. Also, the synthesized zeolite X/glutamic acid composite was identified using various instruments such as XRD, CHN, FT-IR, and FE-SEM. The FE-SEM image confirmed that the fabricated composite has a cotton-like structure. Also, the XRD pattern confirmed the presence of a wide XRD peak at 2Ɵ = 23°. Hence, this confirmed that the crystalline structure of zeolite X interfered or combined over amorphous surroundings. Besides, the synthesized zeolite X/glutamic acid composite was employed as an adsorbent for the efficient removal of Co(II) ions from aqueous media. Moreover, the highest removal efficiency is achieved at pH = 6, time = 100 min, and temperature = 298 K. The experimental results were matched well with the Langmuir equilibrium isotherm and pseudo-second-order kinetic model. The maximum adsorption capacity of the synthesized composite is 120.90 ± 3.94 mg/g. Additionally, the removal of Co(II) ions is chemical, exothermic, and spontaneous.

Efficient removal of Co(II) and Sr(II) from aqueous solution using polyvinyl alcohol/graphene oxide/MnO2 composite as a novel adsorbent

In this study, a novel adsorbent, polyvinyl alcohol/graphene oxide/MnO2 composite was prepared, characterized and used for efficient removal of Co2+ and Sr2+ from aqueous solution. Polyvinyl alcohol (PVA) and Mn2+ played a synergistic role in the gelation of PVA/GO/Mn2+, while Mn2+ can be further converted into oxide to achieve functionalized aerogel (PVA/GO/MnO2). The spectroscopy analysis manifested that hydrogen bonds and electrostatic attraction were responsible for the formation of PVA/GO/MnO2. The functionalization of MnO2 enhanced the adsorption capacity for Co2+ (2.1 folds) and Sr2+ (1.3 folds) by PVA/GO/MnO2. The composite showed high adsorption capacity at broad pH range of 4.0–9.0. For competitive adsorption test, Ni2+/Zn2+ exerted the most interfering effect on Co2+ adsorption, while Mg2+/Ca2+ showed severe interfering effect on Sr2+ adsorption. Both electrostatic attraction and oxygen-containing groups contributed to the adsorption mechanism. This study may provide a new adsorbent for separation of Co2+ and Sr2+ from aqueous solution.

Rapid and efficient removal of CO in CH4 and CH4/coal dust hybrid explosions: A novel approach of spraying catalyst powder

A novel approach of spraying catalyst powder (SCP), based on copper manganese oxide catalyst, has been proposed for CO removal in both CH4 and CH4/coal dust hybrid explosions. The CO removal performance and mechanism of SCP approach in both CH4 and CH4/coal dust hybrid explosions were deeply studied with a standard 20L spherical chamber. The results show with application of SCP approach the CO concentration is decreasing obviously. When adding 200 g/m3 Cu/Mn catalyst, the CO removal efficiency in CH4 explosions and 8% CH4/coal dust hybrid explosions is up to 43.2% and 98.1%, respectively. The remarkable CO removal efficiency is mainly caused by the combination of suppression effect and catalytic oxidation. Inert Al2O3 powder with faint CO catalytic activity was added to find out the influence of suppression effect on CO production. Results demonstrated that suppression effect may promote CO production by lowering explosion temperature in CH4 explosions, while restrain CO production by weakening pyrolysis process of coal dust in CH4/coal dust hybrid explosions. Therefore, SCP approach exhibited better CO removal performance in CH4/coal dust hybrid explosions. Especially, there is an optimum concentration of catalyst powder for CO removal in CH4 explosion owing to the combined effect of catalytic oxidation and suppression behavior. This method offers a novel perspective for CO fast removal in explosion accidents and is promising for practical application in emergence rescue.

Efficient removal of Co(II) from aqueous solution by flexible metal-organic framework membranes

In this work, flexible surface-supported metal-organic framework (MOF) membranes were successfully prepared on fabric by a simple method and used for cobalt adsorption for the first time. MIL-101-NH2 crystals were deposited in-situ on the fabric by hydrothermal synthesis. SEM and XRD results demonstrated that the MOF membranes were robust, stable, and consistent. The influences of pH, temperature, and initial cobalt concentration on the cobalt adsorption capacity of the membranes were investigated. The maximum Co(II) adsorption capacity was found to be 116.3 mg g−1, and the MOF membranes retained excellent adsorption capacity even after ten cycles. The Co(II) adsorption process on the membranes was endothermic and spontaneous and followed pseudo-second-order chemisorption. The XPS analysis implied that the formation of Co2+ and -NH2 complexes dominated the cobalt adsorption process. The application of MOF membranes in Co(II) adsorption simplified the MOF powder recycling process indicating that the easily-prepared and environment friendly flexible MOF membranes have a great potential for engineering applications in cobalt adsorption.

Utilization of rice husk and waste aluminum cans for the synthesis of some nanosized zeolite, zeolite/zeolite, and geopolymer/zeolite products for the efficient removal of Co(II), Cu(II), and Zn(II) ions from aqueous media

In this paper, rice husk and waste aluminum cans were exploited as silicon and aluminum sources, respectively for the low-cost synthesis of some nanosized zeolite, zeolite/zeolite, and geopolymer/zeolite products. XRD confirmed that the synthesized geopolymer/zeolite products are geopolymer/zeolite A (has a crystallite size of 58.44 nm & abbreviated as G1) and geopolymer/faujasite (has a crystallite size of 25.58 and 20.26 nm & abbreviated as G2 and G3, respectively). Also, the synthesized zeolite products are sodium aluminum silicate hydrate (has a crystallite size of 27.65 and 41.85 nm & abbreviated as H1 and H2, respectively). Besides, the synthesized zeolite/zeolite product is sodium aluminum silicate hydrate/zeolite A (has a crystallite size of 66.01 nm and abbreviated as H3). Moreover, the synthesized products were characterized using other tools such as HR-TEM, FE-SEM, EDX, and FT-IR. The synthesized products were efficiently applied for removing Co(II), Cu(II), and Zn(II) ions from aqueous media and wastewater which was taken from Abuzaabal- Qalyubiyah-Egypt. The maximum uptake capacity of G3 sample toward Co(II), Cu(II), and Zn(II) ions is 134.24 ± 1.26, 126.26 ± 0.32, and 131.93 ± 0.87 mg/g, respectively. The uptake of the studied metal ions is spontaneous, chemical, exothermic, and fitted well with the Langmuir isotherm and pseudo-2nd-order kinetic model.

Insight into the efficient co-removal of Cr(VI) and Cr(III) by positively charged UiO-66-NH2 decorated ultrafiltration membrane

To effectively remove total Cr from wastewater, a novel composite membrane (PEI/MOF@PVDF) was successfully prepared by depositing UiO-66-NH2 and subsequently cross-linking with polyethylene imine (PEI) based on polyvinylidene fluoride (PVDF). UiO-66-NH2 was mainly immobilized on the membrane surface and finger-like pore, which reduced the hydrophilicity and improve the surface positive charge, while the cross-linked PEI not only sufficiently covered this shortage but also enhanced the stability of membrane. PEI/MOF@PVDF owned such a high pure water flux as 561 L/(m2·h), meanwhile the water flux of BSA-contaminated membrane could be restored to 96.13%. This is the first work focusing on the efficient co-removal of both Cr(VI) and Cr(III) with the novel positively charged UiO-66-NH2 decorated ultrafiltration membrane (PEI/MOF@PVDF). Interestingly, the effluent concentration of Cr(VI) was broke through at effective treatment volume of 2322.23 L/m2 which was mainly charged by electrostatic attraction with the positive pores. And the effluent concentration of Cr(III) was consistently stable because of Donnan effect on the positive membrane. The EDS mapping revealed that Cr(VI) was preferentially adsorbed in the membrane pores for their high potential with highly concentrated UiO-66-NH2, while Cr(III) was mainly rejected on the positive surface. Moreover, PEI/MOF@PVDF showed negligible leakage of UiO-66-NH2 owing to the successful cross-link of PEI and the membrane can be easily regenerated and reused. Thus, the newly-developed composite membrane showed a promising potential for the efficient co-removal toward both Cr(VI) and Cr(III) in treating authentic wastewater.

Simultaneous removal of butylparaben and arsenite by MOF-derived porous carbon coated lanthanum oxide: Combination of persulfate activation and adsorption

A novel multifunctional material of MOF-derived porous carbon coated lanthanum oxide (donated as La-MOF-900) had been successfully synthesized by hydrothermal-calcination method, which used in the simultaneous removal of butylparaben (BPB) and As(III). For the single contaminant system, the degradation rate of BPB could reach 98% and retain a high removal efficiency in a wide pH range of 3–9, which covered the most wastewater. In contrast, the removal rate of As(III) reached 90% in the pH of 3, and still 70% of the As(III) can be removed in the pH of 9. For the BPB-As(III) binary system, the presence of As(III) had no obvious impact on the degradation rate of BPB. However, the removal rate of As(III) was suppressed at the presence of BPB because of the competitive reaction of radicals between BPB and As(III). O2−, 1O2, HO and SO4− were all involved in La-MOF-900/PS system. The composition of porous carbon in the La-MOF-900 was responsible for activating persulfate to degrease BPB and oxidize As(III) to As(V) while La2O3 component of La-MOF-900 acted as adsorbent for the removal of evolved As(V). The proposed strategy would be very indicative for the efficient co-removal of combined pollutants in the aqueous solution.

Synergistic co-removal of zinc(II) and cefazolin by a Fe/amine-modified chitosan composite

A novel Fe/amine modified chitosan composite (Fe/N-CS) was facilely synthesized and showed higher affinity to both Zn(II) and cefazolin (CEF) than its precursors. Synergistic co-adsorption of them by Fe/N-CS was observed in varied conditions. The adsorption amount maximally increased by 100.1% for Zn and 68.2% for CEF in bi-solute systems. The initial adsorption rate of Zn(II) also improved with CEF. The increasing temperature facilitated coadsorption. The results of the preloading tests, FTIR/XPS characterizations and DFT calculations suggested that (1) both polyamines and Fe sites participated in the adsorption of Zn(II) and CEF, (2) Zn(II) could serve as a new efficient site for CEF, forming [amine-Zn-CEF]/[FeOH-Zn-CEF] ternary complexes, and (3) the co-presence of CEF shielded the electrostatic repulsion between protonated amines and Zn(II), contributing to the enhancement of Zn(II) adsorption. Further, the ion strength exerted positive and negative influences on the adsorption of Zn(II) and CEF, respectively. Additionally, CEF and Zn(II) were successively recovered by 0.1 mol/L NaOH followed by 2 mmol/L HCl. Fe/N-CS could be stably reused five times. The findings imply that Fe/N-CS is promising for the highly efficient co-removal of concurrent heavy metals and antibiotics.

Efficient co-removal of copper and tetracycline from aqueous solution by using permanent magnetic cation exchange resin

This work aimed to examine a permanent magnetic cation-exchange resin (MCER) for synergistic co-removal of Cu(II) and tetracycline (TC) from their mixed solutions. Batch adsorption experiments and characterizations were performed to elucidate the adsorption mechanisms. The adsorption of Cu(II) followed the Langmuir isotherm model in most cases, while Freundlich isotherm model was more suitable for fitting TC adsorption, which was due to the surface coordination between adsorbed Cu(II) and TC and the formation of multilayer MCER-Cu-TC complexes. The equilibrium TC adsorption amount in binary Cu/TC system was about 5.5–13.5 times of that in sole system, whereas Cu(II) uptake was nearly unchanged. Decomplexing-bridging was ascribed as the primary mechanism, which involved the [Cu-TC] decomplexing and [resin-Cu] bridging for TC uptake. Moreover, these MCER microbeads could be reused with negligible loss in adsorption capacity during five adsorption-desorption cycles, indicative of great potential in synergistic co-removal of organics-Cu complexes from aqueous solutions.