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In this study, a novel green tea/Mg-functionalized magnetic nano-adsorbent, denoted as GTE-MgO-Fe3O4 NPs, was developed and applied to the extraction of Methylene Blue (MB) from water-based solutions. The GTE-MgO-Fe3O4 NPs were synthesized by incorporating green tea extracts (GTE) and Mg species onto the surface of Fe3O4 nanoparticles using a hydrothermal method. Characterization analyses corroborated the successful functionalization of the Fe3O4 surface with GTE and Mg species, resulting in a superparamagnetic adsorbent equipped with abundant surface functional groups, which promoted MB adsorption and facilitated magnetic separation. Batch experiments revealed that different operating parameters had an impact on the adsorption behavior, such as adsorbent dosage, pH, coexisting ions, contact time, the initial MB concentration, and temperature. The investigations of adsorption kinetics and isotherms emphasized that the MB adsorption onto GTE-MgO-Fe3O4 NPs was an exothermic process dominated by chemisorption. The experimental adsorption capacity of GTE-MgO-Fe3O4 NPs for MB surpassed 174.93 mg g−1, markedly superior to the performance of numerous other adsorbents. Ultimately, the utilized GTE-MgO-Fe3O4 NPs could be effectively regenerated through acid pickling, retaining over 76% of its original adsorption capacity after six adsorption–desorption cycles, which suggested that GTE-MgO-Fe3O4 NPs was a suitable adsorbent for eliminating MB from effluent. [ABSTRACT FROM AUTHOR]

In this work, a novel chitosan-based magnetic adsorbent [poly(2-(dimethylamino)ethyl methacrylate) grafted magnetic chitosan microspheres, GMCMs] was synthesized by graft polymerization of (2-(dimethylamino)ethyl methacrylate on the surface of magnetic chitosan microspheres (MCMs). The as-prepared GMCMs exhibited significantly enhanced adsorption capacity towards anionic dyes (e.g., Acid Green 25 and Reactive Blue 19) compared with MCMs. It is due to the fact that the abundant tertiary amine groups of the grafted polymer protonated at low pH and the polymer chains stretched as a result of electrostatic repulsions and chain-solvent interactions. The stretched polymer chains provided a variety of adsorption sites, which efficiently adsorbed dyes through electrostatic interactions and hydrogen bonding. While, in alkaline conditions, the tertiary amine groups were deprotonated and the polymer chains collapsed due to hydrophobic interactions, which facilitated the regeneration of the dye-loaded GMCMs at high pH. The regenerated GMCMs showed excellent adsorption performance even after five adsorption–desorption cycles. Besides, the GMCMs could be rapidly separated from aqueous solutions under an external magnetic field. Therefore, the GMCMs materials bear great application potentials in water treatment owing to its high adsorption capacity, pH-responsiveness, facile regeneration and good reusability. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new magnetic composite of FSNCS/SDBS was synthesized at low temperature. • FSNCS/SDBS shows excellent adsorption performance for CIP. • FSNCS/SDBS shows wide pH adaptability. • SDBS enhances CIP's adsorption by improving the surface charge of FSNCS. In this study, a novel magnetic nickel cobalt sulfide/sodium dodecyl benzene sulfonate (FSNCS/SDBS) adsorbent was synthesized successfully by a facile protocol and was developed to remove ciprofloxacin (CIP) for water purification. The FSNCS/SDBS adsorbent is featured with excellent CIP adsorption capacity of 625 mg·g−1 (much higher than reported most adsorbents), wide pH adaptability (little changed CIP adsorption capacity in pH 6–11), and good magnetic property. The effects of pH and ionic strength on CIP adsorption were investigated. The calculative thermodynamic parameters indicated that CIP adsorption by FSNCS/SDBS was spontaneous and exothermic. CIP adsorption followed pseudo-second-order kinetics and an isotherm best fit with the Langmuir adsorption mode. The adsorption mechanism of CIP onto FSNCS/SDBS was proposed and demonstrated, which included the electrostatic interaction, π–π interaction, coordination with metal and hydrogen bonding. [ABSTRACT FROM AUTHOR]

• Multifunctional magnetic composite nanoparticles were facilely prepared. • The as-prepared FS@CS-PAA showed excellent adsorption capacities for cationic dyes. • FS@CS-PAA exhibited satisfactory removal rates for metal ions in a wide pH range. • The good adsorption ability was attributed to abundant active sites from CS-PAA. • FS@CS-PAA's good stability and reusability facilitated its practical application. Wastewater containing highly toxic, non-biodegradable and carcinogenic organic dyes and metal ions has been regarded as a severe threat to ecological environment and human health. Thus, it is of great significance to develop an effective approach to purify this kind of wastewater. Herein, novel magnetic adsorbent FS@CS-PAA was facilely prepared by coating anionic polyacrylamide-modified chitosan (CS-PAA) on the surface of silica-combined Fe 3 O 4 (FS). The morphology, structure, physic-chemical and magnetic properties of as-prepared FS@CS-PAA were fully characterized by various characterization techniques. Its adsorption behaviors towards cationic dyes and metal ions were systematically investigated in single systems, binary systems, and model wastewater. FS@CS-PAA was proved to have superior adsorption capacities of 2330.17 and 1044.06 mg g−1 respectively for crystal violet and methylene blue at 318.15 K, much higher than other reported adsorbents. Besides, FS@CS-PAA exhibited a pH-independent adsorption capability for metal ions, as demonstrated in single systems and in metal ion-dye binary systems, thus it could be used to treat a variety of metal ion wastewaters with different pH values. Moreover, FS@CS-PAA could be effectively and easily regenerated by HCl solution after the treatments of both synthetic wastewater and model wastewater. As revealed in FTIR and XPS analyses, the adsorption mechanism was mainly attributed to the electrostatic interaction, hydrogen bonding, cation exchange and chelating effect. With its excellent adsorption capacity for cationic dyes, pH-independent adsorption capability for metal ions, easy separation ability, satisfactory stability and good reusability, FS@CS-PAA can become an ideal candidate for wastewater treatment. [ABSTRACT FROM AUTHOR]

Wastewater containing dyes poses a severe threat to human health and to environmental safety. Hence, finding an effective way to treat this wastewater has attracted wide attentions. In this study, quaternary ammonium group-rich magnetic nanoparticles (MNPs), Fe 3 O 4 @SiO 2 -MPS-g-DAC (FSMD), were facilely prepared by grafting polymerization and served as a cationic adsorbent to remove anionic dye Orange G from aqueous solutions. Being compared with Fe 3 O 4 @SiO 2 -MPS MNPs, the adsorption capacity of FSMD MNPs was notably enhanced and it could be maintained in a high level under a wide solution pH range. The dependency on pH and the sensitivity to ionic strength indicated that the main adsorption mechanism was the electrostatic interaction. The adsorption kinetics followed the pseudo-second-order model, and the adsorption isotherms were well described with the Langmuir model. According to the thermodynamic analysis, the adsorption process was spontaneous and endothermic. FSMD MNPs were proved to have advantages of fast adsorption rate, high adsorption capacity, easy separation ability under external magnetic field, and satisfactory reusability, therefore they can be applied in the removal of anionic dyes from wastewater. [ABSTRACT FROM AUTHOR]

The removal of methylene blue (MB) from wastewater has attracted global concerns. In this study, polymer-functionalized magnetic nanoparticles for MB removal, Fe3O4@SiO2-MPS-g-AA-AMPS (FSMAA), were successfully synthesized by grafting acrylic acid (AA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) on the surface of vinyl-modified Fe3O4@SiO2. With various characterization techniques, it was confirmed that the obtained FSMAA had a core–shell structure, a good magnetic property, and plenty of functional groups on its surface. MB adsorption experiments showed that the adsorption capacity of FSMAA was notably enhanced as the grafted monomer concentration and solution pH were increased. The adsorption kinetic data and isothermal data were well described by the pseudo-second-order kinetic model and the Langmuir model, respectively. The maximum adsorption capacity of FSMAA was 421.9 mg g−1 with grafted monomer concentration at 2.0 mol L−1 and solution pH at 9, much higher than those of other adsorbents stated in previous literatures. Based on XPS analysis, surface adsorption mechanism between FSMAA and MB was electrostatic interaction, hydrogen bonding, and hydrophobic interaction. Furthermore, FSMAA was effectively regenerated by acid pickling, and the remaining adsorption capacity was more than 60% after eight adsorption–regeneration cycles. All the results demonstrated the self-made FSMAA was a desirable adsorbent to remove MB from wastewater. [ABSTRACT FROM AUTHOR]

With the rapidly increased discharges of various complex dyeing wastewaters, adsorbents are required to own more properties such as cost-effectiveness, amphoteric ability, and rapid solid-liquid separation ability, to treat dyeing wastewaters. A multi-functional adsorbent was synthesized by co-grafting m-phenylenediamine and sodium allyl sulfonate on the surface of a low-cost base-material: hollow glass microsphere (HGM). Characterization results indicated the surface roughness and –Si–OH groups of HGM were increased by NaOH corrosion; functional groups such as aromatic-rings, –NH 2 , and –HSO 3 − were grafted on the surface of HGM. The synthesized adsorbent showed amphoteric attraction abilities for anionic acid green 25 and cationic basic fuchsin dyes. Kinetics and isotherms studies suggested the PSO model and Langmuir model were most satisfactory for adsorption processes, the theoretical maximum adsorption capacities for acid green 25 and basic fuchsin reached 454.55 and 588.24 mg g−1, respectively. The mechanism investigations indicated the electrostatic attraction, π-π stacking, and hydrogen bonds were the potential interaction forces between dyes and adsorbents. The synthesized material owns self-floating ability due to the hollow structure of HGM, over 95.7% of adsorbents were collected at water surface via the self-floating process in 12 min, which was beneficial to the solid-liquid separation process and the reuse of adsorbents. The technologies developed by these research efforts can serve as templates for synthesizing multi-functional adsorbents for complex wastewaters decontaminations. [Display omitted] • First demonstration of an amphoteric self-floating adsorbent. • The adsorption capacities of anionic/cationic dyes reached 454.55/588.24 mg g−1. • Electrostatic force, π-π stacking, hydrogen bond were dominant adsorption mechanisms. • Over 95.7% of adsorbents were collected at the water surface within 12 min. • The multi-functional adsorbent is beneficial for cleaner production of dyeing goods. [ABSTRACT FROM AUTHOR]

[Display omitted] • The synthesized adsorbents captured 94.18 mg g−1 of Co2+ and 62.56 mg g−1 of Ni2+. • <1% of lithium was lost in the cathode leachate during the separation process. • The dominant capture mechanism conversed from physical to chemical adsorption. • The N atoms on the adsorbents were the effective chemical adsorption sites. • Particle movement track in water was predictable via the proposed equation. The effectiveness of lithium recovery determines the future use of the devices powered by lithium-ion batteries (LIBs) under lithium resource shortages. Selective separation of Co2+/Ni2+ from the cathode leachate of LIBs is a key step to reduce the lithium loss in the recovery progress. This study reported a hollow structured self-floating adsorbent synthesized by co-grafting of (3-Aminopropyl)triethoxysilane (APTES) and ethylenediaminetetraacetic acid (EDTA) on hollow glass microsphere (HGM) for selective capture of Co2+/Ni2+ from LIBs cathode leachate. The introduction of the N atom of APTES was crucial for bridging the inorganic HGM and organic EDTA. The organic component of the synthesized adsorbent accounted for 12.82%, which was responsible for the Co2+/Ni2+ adsorptions. Physic- and chemic-adsorptions were the ordinal mechanisms during the three-stages divided adsorption progress. The negative –COO− groups promoted the electrostatic attraction between metal ions and the adsorbents. The N atoms of EDTA were the effective adsorption sites for Co2+ and Ni2+ ions, resulting in chemical chelation of the metal ions with adsorbents followed by ion exchanges of Na+ and Ca2+. The adsorbents captured 94.18 mg g−1 of Co2+ and 62.56 mg g−1 of Ni2+ with a < 1% lithium loss in the LIBs cathode leachate. The self-flotation process of the adsorbent was non-linearly fitted by our original equation for predicting its movement track for further solid–liquid separation. This research proposed a new strategy for the selective adsorption of Co2+/Ni2+ from LIBs cathode leachate with limited lithium loss. [ABSTRACT FROM AUTHOR]