•A novel porphyrin-functionalized cotton fiber (CPT) for Cd2+ was prepared.•The CPT exhibited color response and enhanced adsorption performance to Cd2+.•A linear relationship used to determine the concentration of Cd2+ was established.•The color of the CPT changed within 2 min in response to Cd2+.In this study, a porphyrin functionalized cotton fiber was prepared and investigated for the visual detection and efficient adsorption of cadmium (Cd2+) ions in aqueous solutions. The pristine cotton fiber was first grafted with poly (3-sulfopropyl methacrylate potassium salt) (PSMP) via the surface-initiated atom transfer radical polymerization (SI-ATRP), and subsequently immobilized with 5,10,15,20-tetrakis(1-methy-4-pyridinio)porphyrin tetra(p-toluenesulfonate) (TMPyP), to form the CPT (Cotton-PSMP-TMPyP) material. The CPT was characterized by SEM, FTIR, XPS and elemental analysis, and examined for the detection and adsorption of cadmium ions. The influencing factors such as pH and the initial cadmium ion concentrations on the adsorption performances were investigated. Results showed that the cadmium ion adsorption isotherm was best fitted with the Langmuir isotherm model, with the derived maximum adsorption capacity of 0.8638 mmol/g. The thermodynamic study showed the endothermic nature of the adsorption process. In addition, the adsorption kinetics was fast with over 90% of the total cadmium ions adsorbed within 2 min. Furthermore, the distinctive color response of the CPT to the cadmium ions in aqueous solutions was clearly displayed. A linear relationship between the light absorbance of CPT-Cd (CPT adsorbed with cadmium ions) and the initial concentrations of cadmium ions was successfully established, which could be used for the fast determination of the cadmium ion concentrations in aqueous solutions.

•Removal of heavy metal ions by LbL assembled FO membranes was investigated.•The five heavy metal ion rejection during the FO process exceeded 99.31%.•Heavy metal ion adsorption on FO membranes played an important role in the high rejection.The removal performances of heavy metal ions with the layer-by-layer (LbL) assembled forward osmosis (FO) membranes were investigated in this study. The prepared FO membrane with the multi-layer polymer network was fabricated by assembling multiple polyethylenimine (PEI) and sodium alginate (SA) bilayers on a polydopamine-functionalized polyvinylidene fluoride (PVDF) supporting membrane. The prepared FO membrane possessed high rejection of five heavy metal ions, i.e., Cu2+, Ni2+, Pb2+, Zn2+ and Cd2+. The influences of different osmosis modes, number of bilayers, pH, time, temperature, regeneration as well as the concentration of feed and draw solutions on the heavy metal ion removal performances of the FO membrane were studied. Results showed that all the heavy metal ion rejections with the 3-layer assembled FO membranes exceeded 99.31% in AL-FS (the active layer facing the feed solution) mode when 1 M MgCl2 was employed as the draw solution, and the rejection in AL-FS mode was higher than that in AL-DS (active layer facing the draw solution) mode. The experimental results revealed that the number of bilayers of the polyelectrolyte pairs, the hydrated radii of metal ions and the heavy metal ion adsorption all contributed to the high rejection of the heavy metal ions.

•A facile strategy to synthesize HCPs using WEPS as raw material was proposed.•DCE was used as solvent and crosslinking agent in synthesis of the HCPs.•The HCPs exhibited large specific surface area and good thermal stability.•The HCPs possessed high CO2 adsorption capacity and selectivity over N2.A novel facile and one-pot approach was developed for the preparation of hyper-crosslinked polymers (HCPs) via the Friedel-Crafts reaction between the waste expanded polystyrene foam (WEPS) and 1,2-dichloroethane in this study. 1,2-dichloroethane as a cost-effective chemical agent was used as both the solvent and the cross-linker for HCPs. The obtained HCPs showed large specific surface areas and good thermal stability. The highest CO2 adsorption capacity (1.987 mmol/g) and the adsorption selectivity ratio (CO2 over N2) of 23.4 at 273 K and 1.13 bar were achieved among the prepared HCPs. This study provides a simple and cost-effective method to convert WEPS into value-added adsorbents for the capture and storage of carbon dioxide as the greenhouse gas.Download high-res image (136KB)Download full-size image

In this study, an amino functionalized cotton fiber, which was used to adsorb Cu2+ ions via visible sequestration, was prepared and investigated. The amino-functionalized cotton fiber (named as ACF) exhibited enhanced adsorption, selectivity and distinct color response to Cu2+ ions in aqueous solutions. The absorbance responses of ACF to Cu2+ ions (named as ACF–Cu), obtained from the a fiber optic spectrometer, were monitored with different pH values and initial Cu2+ ion concentrations. A linear relationship between the absorbance response and the initial concentrations of Cu2+ ions was established and can be used for the determination of Cu2+ ion concentrations in aqueous solutions. Furthermore, in the interference study, ACF showed great selectivity to Cu2+ ions when other ions (e.g., Pb2+ or Zn2+ ions) coexisted with the Cu2+ ions in solution. The ability of ACF to effectively detect Cu2+ ions with the presence of other interfering ions in solution was of great significance.

Different amounts of CuO are used to synthesize CaCu3+xTi4O12 (CCxTO, −1 ≤ x ≤ 1) powders in this work. In order to investigate the effects of Cu constituent on the componential, morphological, and dielectric properties, 975 °C is selected as the sintering temperature to prepare the ceramic pellets with different x values from −0.2 to 0.2. They basically keep the same component and morphology despite the different Cu constituents in the ceramics. Cu component has complex effects on their dielectric properties, whose changes are not linear with the Cu increase. However, the CC0.2TO ceramic sample has the most frequency-independent dielectric constant and the lowest dielectric loss.

•ZnO nanoparticles as templates were used to prepare PVDF porous membranes.•The microstructure of the supporting layer could be optimized by etching method.•The optimized channels alleviated the concentration polarization in the FO membrane.The physical and chemical characteristics of the porous supporting layer play a key role in the separation efficiency and concentration polarization of the forward osmosis (FO) membranes. In this paper, the modified polyvinylidene fluoride (PVDF) porous membranes with high porosity and large amounts of surface membrane pores were prepared with zinc oxide (ZnO) nanoparticles as the template, and used as the supporting layer of the FO membrane. The modified FO membranes showed enhanced water permeability and separation selectivity. The increased water flux was based on the increase of the effective membrane area, and the decreased τ/ε (tortuosity factor/porosity) value obviously alleviated the concentration polarization phenomenon based on the optimization of the flow channel. The etching of the porous microstructure could reduce the limit of the supporting layer on the separation performance of the FO membrane, and provide a simple method to improve the separation efficiency of the thin film composite (TFC)-type FO membranes.

•A novel TFC type FO membrane with inserted sublayer was prepared.•The effect of sublayer on FO performance was investigated.•CNT sublayer provided a three-dimensional free space for separation process.The purpose of this study was to reveal the effect of the sublayer structure on the separation performance of the thin film composite (TFC)-type forward osmosis (FO) membranes. A novel TFC-type FO membrane with a supporting layer of polyvinylidene fluoride (PVDF) porous membrane, a sublayer of carbon nanotube (CNT) network and an active skin layer of polyamide (PA) was prepared by a simple filtration-assisted interfacial polymerization method. The results showed that the prepared FO membrane exhibited the improved separation efficiency, with twice the water flux of the FO membrane without this CNT sublayer. The characterization of the prepared FO membrane structure revealed that the presence of the CNT sublayer was favorable for providing a three-dimensional free space, which increased the effective area of the PA layer by optimizing the space structure underneath the PA layer. At the same time, the experimental results demonstrated the negative effects of the conventional supporting layer structure on the separation performance and concentration polarization of the FO membrane, and highlighted the important role of the sublayer structure between the active skin layer and the supporting layer for the performance improvement of FO membranes.