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The solid-liquid separation ability of adsorbents is of great significance for improving the recovery efficiency and reducing the cost. Herein, a novel floating-magnetically responsive silica adsorbent (FMSA) was prepared and applied to the adsorption of cationic dyes from aqueous solution. FMSA with self-floating and magnetic response properties exhibited great solid-liquid separation ability and adsorption performance for cationic dyes. According to the Langmuir model, the theoretical saturated adsorption capacity of FMSA for Basic Blue 7 (BB-7) and Crystal Violet (CV) reached 1632.55 mg g−1 and 1587.23 mg g−1, respectively. Thermodynamic experiments manifested that the adsorption was a spontaneous endothermic process with increasing entropy. After 5 adsorption-desorption processes, FMSA's adsorption capacity for BB-7 and CV remained above 80%, indicating that it has satisfactory stability and reusability. Furthermore, the pH effect, isotherm, kinetics, ion interference experiments and characterization analysis manifested that the adsorption was mainly chemical adsorption with an ion exchange process. This research aims to bring some inspiration for the combined use of floating separation and magnetic separation to achieve more flexible, efficient and energy-saving solid-liquid separation. [Display omitted] • A floating-magnetically responsive silica adsorbent was successfully developed. • Obtained adsorbent has both self-floating ability and magnetic response properties. • FMSA showed great reusability and resistance to ion interference. • BB-7 and CV were efficiently removed in a wide pH range. • Powerful electrostatic interaction and ion exchange ensure efficient adsorption. [ABSTRACT FROM AUTHOR]

Natural polymeric flocculants as sludge conditioners have received great attention due to their non-toxic and biodegradable advantages. However, the application of amphiphilic natural flocculants as sludge conditioners is rarely reported. In this work, the novel chitosan-based flocculants (CS-g-PAO) with amphiphilic structure were synthesized by ultraviolet light initiated method for the enhancement of sludge dewatering performance. The solubility of CS-g-PAO was significantly improved in a wide pH range (2.0–10.0). Various characterization methods were used to investigate the structure, thermal stability and surface morphology of copolymers, suggesting the successful synthesis of CS-g-PAO. In dewatering experiments, CS-g-PAO showed superior dewatering performance, and filter cake moisture content could be decreased to 77.98% from 95.14%. Moreover, the results of extracellular polymeric substances (EPS) components indicated that hydrophobic effect of CS-g-PAO was beneficial to remove the protein in S-EPS and TB-EPS, which had the crucial influence on dewatering performance. Furthermore, the dewatering mechanism was discussed based on the effects of zeta potential, apparent viscosity, surface tension and flocs structure on dewaterability. Results revealed that CS-g-PAO had strong hydrophobic association effect and surface activity. In addition, enhanced charge neutralization and hydrophobic interaction played a synergetic role in improving the dewaterability of CS-g-PAO. Image 1 • A novel chitosan-based flocculant with amphiphilic structure was synthesized. • The water solubility of the amphiphilic flocculant was improved in a wide pH range. • The amphiphilic flocculant showed superior dewatering efficiency under low dosage. • All results confirmed the role of charge neutralization and hydrophobic attraction. [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]

In this paper, a novel magnetic sorbent based on silica coated iron oxide (Fe 3 O 4 /SiO 2 , denoted as FS), poly(ethylene imine) (PEI), sodium p-styrenesulfonate (SPS) and sodium alginate (SA) polymer (Fe 3 O 4 /SiO 2 /SA-PEI-SPS, denoted as FSSEP) is successfully prepared by free radical polymerization. Antibiotic (ciprofloxacin, CPX), dye (methylene blue, MB) and heavy metal (copper ion, Cu2+) are used to test the adsorption capacity of the prepared adsorbent. Compared with other adsorbents, FSSEP exhibited good capture efficiency for the pollutants in this study, especially for organic pollutants (CPX and MB). The maximum sorption capacity of FSSEP reached 203.99 mg g−1 for CPX, 423.69 mg g−1 for MB, 41.81 mg g−1 for Cu2+. Hydrogen bonding, electrostatic interaction, π-π interaction and cationic exchange are involved in the sorption mechanism. This study suggests a strategy for the design and synthesis of eco-friendly modified sodium alginate adsorbents through free radical polymerization and explores their potential application in the field of removal of different types of toxic substances. [Display omitted] • A new magnetic composite of FSSEP was synthesized by free radical polymerization. • Dye (MB), antibiotic (CFX) and Cu2+ ion were efficiently captured via FSSEP. • FSSEP microparticles can be regenerated and quickly separated from solution. • Adsorption mechanism of FSSEP was analyzed and discussed in this work. [ABSTRACT FROM AUTHOR]

The metal activating sulfite system has attracted widespread attention as a novel advanced oxidation process recently. In this study, a silica-supported highly dispersed cobalt catalyst was prepared using Co ammine complex as precursor, characterized by transmission electron microscope, X-ray diffraction, Brunauer–Emmett–Teller surface area, X-ray photoelectron spectroscopy and so forth, and used to activate sulfite for the removal of organic pollutants. The as-prepared catalyst displayed a durable and remarkable catalytic activation of sulfite for organic degradation in sequential experiments. The mechanistic study corroborated the dual roles of sulfite as a complexing ligand on catalyst surface and a precursor of oxysulfur radicals. The surface-bound and free SO 4 •− were found to be the dominating radicals responsible for organic degradation. The steady-state approximation of SO 4 •− were examined and the apparent reaction rate constant of SO 4 •− generation was 0.60 ± 0.07 M−1 s−1 at 0.25 g L−1 catalyst. The influencing factors and operating parameters, including catalyst dosage, sulfite/contaminant ratio, pH, temperature, anions and natural organic matter were investigated and optimized systematically. As conclusion, the as-prepared catalyst to efficient activation of sulfite can be proposed as a promising advanced oxidation process based on oxysulfur radicals for the treatment of wastewater. Image 1 • The silica-supported cobalt catalyst is synthesized via a complexation process. • CoASi shows an effective performance in sulfite activation for organic degradation. • Sulfite acts as a complexing ligand and a radical precursor in activation process. • Surface-bound and free sulfate radicals are responsible for dye degradation. • The optimal operating conditions are obtained for further application. [ABSTRACT FROM AUTHOR]