•MIL-101(Cr)/natural polymer composites possess enhanced separability from water.•MIL-101(Cr)/chitosan composite beads exhibit high adsorption capacity.•Cr centers of MOFs and NH2 of chitosan have charge attraction with contaminants.•Strong π-π interaction also contributes to the adsorption.Porous metal-organic frameworks (MOFs) have great potential as high-effective adsorbents for water treatment. However, poor separability restricts their practical application. To overcome the drawback, both MIL-101(Cr)/sodium alginate (MIL-101(Cr)/SA) and MIL-101(Cr)/chitosan (MIL-101(Cr)/CS) composite beads were prepared and characterized. Adsorption of three selected pharmaceuticals and personal care products (PPCPs) (benzoic acid (BEN), ibuprofen (IBU) and ketoprofen (KET)) onto the two composite beads was investigated and compared with pristine SA and CS beads. Kinetic plots, pH dependence, isotherm data, and influences of ionic strength were reported. The MIL-101(Cr)/CS beads exhibit much higher adsorption capacity than SA, CS and MIL-101(Cr)/SA, and the adsorption amounts of three PPCPs onto MIL-101(Cr)/CS follow the order of KET > IBU > BEN. The adsorption amounts of the three PPCPs on the MIL-101(Cr)/CS increased quickly during the first 60 min of contact time and then achieved the adsorption equilibrium after ∼180 min. Not only the protonated amine groups but also the Cr center of the adsorbents exerted electrostatic attraction with the deprotonated carboxyl groups of contaminants, as elucidated by X-ray photoelectron spectroscopy (XPS). Based on the adsorption isotherms and π-energy analysis of three PPCPs, π-π interaction of aromatic groups between adsorbents and contaminants also contributed to the adsorption. The MIL-101(Cr)/CS beads exhibited good regenerability over several repeated adsorption/desorption cycles. Overall, this study is believed to enlarge the application of MOFs on the removal of emerging contaminants from waters.Download high-res image (231KB)Download full-size image

•Sulfamic/amino acids modified polyaspartic acid scale inhibitors are prepared.•The scale inhibitors have high scale inhibition capacities against calcium sulfate.•DFT calculation gives quantitative explanation of inhibition mechanism.•Inhibitors prevent the growth of crystal planes ({040}, {041} and {113}).•Differential UV spectra show Ca2 + is controlled by carboxylic and phenolic hydroxyl.Modified polyaspartic acid (PASP) scale inhibitors, Tyr-SA-PASP and Trp-SA-PASP, were prepared through grafting copolymerization on PASP with sulfamic/amino acids, and then applied for the inhibition of calcium sulfate from cooling water. Scale inhibition performance evaluation demonstrated Tyr-SA-PASP and Trp-SA-PASP were two cost-effective scale inhibitors for the inhibition of calcium sulfate: Compared to PASP and two commercial scale inhibitors (PAPEMP and JH-907), both modified PASP scale inhibitors exhibited higher inhibition performance, due to coordination between the deprotonation of carboxylic acid and phenolic hydroxyl groups of Tyr-SA-PASP and carboxylic acid groups of Trp-SA-PASP and Ca2 +. Scale inhibition mechanism was investigated from microscopic viewpoints: coordination was the intrinsic driving force; Modified PASP scale inhibitors significantly damaged the crystalline structure of calcium sulfate scale, which resulted from coordination between functional groups on modified PASP scale inhibitors and Ca2 +; The scale inhibition ability of modified PASP scale inhibitors came from the prevention of the growth of crystal planes ({040}, {041} and {113}). The current study provided a strategy for the design of scale inhibitors from the viewpoint of chemical structures.Download high-res image (110KB)Download full-size image

•New nanocomposite adsorbent ZIF-67/D201 is prepared by an alternate deposition method.•ZIF-67/D201 exhibits enhanced adsorption capacity to BTA.•ZIF-67/D201 has selective affinity to BTA when BTA with similar structure coexists.•Density functional theory (DFT) calculation is used to clarify adsorption mechanism.•A strategy for precise separation of pollutants with similar structure is provided.A new nanocomposite adsorbent ZIF-67/D201, in which nanocrystalline ZIF-67 were immobilized inside the networking pores of a commercial polystyrene anion exchanger D201 by an alternate deposition method, with high capacity and enhanced selective affinity toward benzotriazole (BTA) was fabricated and characterized. ZIF-67/D201 demonstrated precise selective adsorption of BTA when benzimidazole (BMA), with very similar chemical structure to BTA, coexisted. After the uptake of BTA, ZIF-67/D201 could be regenerated for repeated use with slight capacity loss. According to kinetics data, two diffusion steps driven by electrostatic attraction were found prior to adsorption equilibrium: a fast diffusion of the contaminant into mesopores of D201 and then a relatively slow diffusion into micropores of ZIF-67. The underlying mechanism for the enhanced selective adsorption was revealed by spectral analysis and density functional theory (DFT) calculations. Three sorts of interactions (coordination, electrostatic attraction and π-π interaction) contributed to the fixing of contaminants. Among them, coordination was the predominant effect. For each sort of interaction, the binding energy of adsorbent-BTA was always larger than that of adsorbent-BMA, which was the intrinsic reason of the high selectivity in molecular level. The above results provided a strategy for precise separation of components with similar structures in water.Download high-res image (155KB)Download full-size image

Complex interactions between antibiotics and graphene-based materials determine both the adsorption performance of graphene-based materials and the transport behaviors of antibiotics in water. In this work, such interactions were investigated through adsorption experiments, instrumental analyses and theoretical DFT calculations. Three typical antibiotics (norfloxacin (NOR), sulfadiazine (SDZ) and tetracycline (TC)) and different graphene-based materials (divided into two groups: graphene oxides-based ones (GOs) and reduced GOs (RGOs)) were employed. Optimal adsorption pHs for NOR, SDZ, and TC are 6.2, 4.0, and 4.0, respectively. At corresponding optimal pHs, NOR favored RGOs (adsorption capability: ∼50 mg/g) while SDZ preferred GOs (∼17 mg/g); All adsorbents exhibited similar uptake of TC (∼70 mg/g). Similar amounts of edge carboxyls of both GOs and RGOs wielded electrostatic attraction with NOR and TC, but not with SDZ. According to DFT-calculated most-stable-conformations of antibiotics-adsorbents complexes, the intrinsic distinction between GOs and RGOs was the different amounts of sp2 and sp3 hybridization regions: π–π electron donor–acceptor effect of antibiotic-sp2/sp3 and H-bonds of antibiotic-sp3 coexisted. Binding energy (BE) of the former was larger for NOR; the latter interaction was stronger for SDZ; two species of TC at the optimal pH, i.e., TC+ and TC0, possessed larger BE with sp3 and sp2 regions, respectively.Keywords: antibiotics; electrostatic attraction; graphene derivatives; hydrogen bond; interactions; π−π electron donor−acceptor effect