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Eradication of heavy metals and dyes simultaneously from wastewater is urgently needed to safeguard public and environmental health. In this study, magnetic porous biochar derived from wasted Myriophyllum aquaticum (MPMaB) was synthesized by KOH-activation and co–precipitation method to treat chromate and rhodamine B (RhB)-bearing wastewater. The KOH activation significantly improved the pore structure of biochar with a high specific surface area of 937.1 m2 g−1. The sorption performance of MPMaB for Cr(VI) and RhB in single and co-solutes conditions was evaluated. In single system, a pH-dependent sorption pattern for Cr(VI) by MPMaB was revealed and the estimated sorption capability reached 175.4 mg g−1, whereas the Langmuir-based sorption capacity of RhB was 175.4 mg g−1 pH-independently. MPMaB partially transformed Cr(VI) to less toxic Cr(III) (approximately 59.3%). Synergistic sorption of Cr(VI) with the coexistence of RhB was observed, where synergistic effect ranged from 119% to 527% depending on pH. For example, the sorption capacity of Cr(VI) on MPMaB, at pH 2, augmented from 175.4 mg g−1 (single system) to 208.3 mg g−1 (binary system). Preferential sorption of Cr(VI) was found and was further confirmed by the post-sorption of Cr(VI) (or RhB) by MPMaB pre-sorbed with RhB (or chromate). Chromate sorption mechanisms mainly include electrostatic interactions and complexation, while the sorption of RhB is ascribed to π–π interactions, pore filling and hydrogen bonding. Additionally, MPMaB showed excellent reusability and maintained high removal efficiency after 5 cycles. In short, MPMaB can efficiently treat chromium and dyes–containing wastewater as sustainable and environmentally friendly adsorbent. [Display omitted] • Wasted macroalgae was used to synthesize magnetic porous biochar with high SSA. • MPMaB exhibited excellent sorption ability for Cr(VI) and RhB with good reusability. • SynErgistic sorption (119%–527%) of Cr(VI) was revealed with coexistence of RhB. • Preferential sorption of Cr(VI) than RhB was observed at pH 2. • MPMaB can partially transformed Cr(VI) to Cr(III), concurrent with Cr(VI) sorption. [ABSTRACT FROM AUTHOR]

In order to promote the convenience and environmental friendliness of recycling process for the magnetic nanoparticles (MNPs) used in emulsified oil-water separation, a series of recyclable multi-responsive MNPs were successfully fabricated via grafting triple sensitive copolymers onto the silica coated ferroferric oxide (Fe 3 O 4 @SiO 2) nanoparticles. It was found that the performance of fabricated MNPs was significantly influenced by three environmental parameters, namely pH value, temperature and ionic strength (IS) of water. The synthesized MNPs tended to assemble at oil droplet surface at a temperature less than lower critical solution temperature (LCST), lower pH level or higher IS, thereby facilitating removal of emulsified oil from water phase under external magnetic field. On the contrary, these MNPs could also reversibly desorb form oil droplet surface at a temperature higher than LCST, higher pH level or lower IS. Accordingly, the spent MNPs could be easily regenerated by just regulating solution temperature, pH or IS, rather than by washing with organic solvent, thereby minimizing the risks of secondary pollution. Recycling experiment showed that the well-designed MNPs could be reused up to five cycles without showing remarkable decline in separation efficiency. It's noteworthy that the MNPs exhibited superior separation efficiency at high IS, which is typically encountered for real saline oily water system, thereby spent MNPs could be easily recycled by merely using deionized water due to the dramatical decrease of IS during their rinsing process, suggesting its applicability for practical use. It is expected that the development of this multi-responsive and recyclable MNPs can potentially offer a promising, facile, cost-efficient and eco-friendly route for the emulsified oily wastewater treatment. Image 1 • Temperature, pH and IS-responsive MNPs were fabricated for oil-water separation. • The MNPs exhibited superior performance at lower pH, lower temperature or higher IS. • Spent MNPs could be regenerated by raising pH, raising temperature or decreasing IS. • The MNPs could be recycled at least five times with negligible reduction in efficiency. • The MNPs were particularly applicable to treat practical saline oily wastewater. [ABSTRACT FROM AUTHOR]

• The properties of carboxylated chitosan/trimesoyl chloride membrane were tailored. • Mid-drying facilitated the permeation flux and salt rejection of the membrane. • The membrane performance was susceptible to the phase transfer catalyst. Thin-film composite polyesteramide nanofiltration membrane prepared from carboxylated chitosan and trimesoyl chloride was carefully tailored during its fabrication process of interfacial polymerization. The effects of post-curing, mid-drying and the addition of phase transfer catalysts on the membrane properties were studied using single-factor experiment. Post-curing was found to be effective in improving the separation performance of the membrane containing high concentrations of carboxylated chitosan, and the optimal post-curing effect was achieved at a temperature of 40 °C and curing time range of 15−20 min. Mid-drying enhanced the permeation flux and salt rejection of the membrane containing low concentrations of carboxylated chitosan, and the optimum temperature range for the mid-drying process was obtained at 30−40 °C. Furthermore, the membrane properties were susceptible to the addition of phase transfer catalysts, and a uniformly distributed phase transfer catalyst is vital to its influence on membrane properties. The addition of 0.025 wt% benzyltriethylammonium chloride to the aqueous solution exhibited the best effect towards the improvement of the separation performance of the produced membrane. [ABSTRACT FROM AUTHOR]

Ti 3 C 2 T x MXene has been reported to be a metallic two-dimensional (2D) material with high conductivity, whereas its photoluminescence (PL) mechanism is still under debate. Herein, we demonstrate that large Ti 3 C 2 T x MXene flakes exhibit tunable PL under ambient conditions. The as-prepared Ti 3 C 2 T x MXene flakes emit blue, yellow-green and red light under different excitation wavelengths. Their PL emission wavelengths redshift as the excitation wavelength changes from violet to red light. Surface modification of the MXenes can further tune the PL peak wavelength into the near infrared region. Using density function theory (DFT) calculations, this excitation wavelength-dependent PL can be correlated to TiO 2 defects that exist on the surface of Ti 3 C 2 T x. Our study expounds on the optical properties of Ti 3 C 2 T x MXene and is helpful for comprehensively understanding this novel material. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) have been recognized to have great potential for the treatment of heavy metals in wastewater and soil through various mechanisms. Isomorphic substitution is an important mechanism for the sorption of heavy metal cations with LDH reconstruction and highly stable product formation. However, sorption performance, structure-related relationships, and, more importantly, stability are still poorly understood. In this study, a series of LDHs with different structures were synthesized to evaluate their cadmium (Cd) sorption performance and stability concerning the isomorphic substitution mechanism. Divalent cation types in the LDH lattice determined the Cd sorption capacity as well as the isomorphic substitution possibility, following the order of hydroxide solubility of divalent cations (MII): Ca2+>Mg2+>(Cd2+) > Ni2+>Zn2+. In addition, CaAl-LDH exhibited a super-high Cd sorption capacity of 625.0 mg g−1. Cd sorption by LDHs with different interlayer anion types and divalent/trivalent cation molar ratios varied due to crystallite size-related MII release through cation-exchange/isomorphic substitution. Coexisting cations (e.g., Zn2+, Ni2+, Mg2+) influence the sorption performance of MII-LDH mainly through isomorphic substitution mechanism, largely depending on the solubility of MII(OH) 2 with a trend of stable product formation. Furthermore, Mg 2.9 Cd 0.1 AlCl-LDH was fabricated, and limited Cd dissolution without destruction of the LDH structure was observed under various conditions. For example, only 7.69%, 2.16% and 0.96% of Cd was released from as-prepared Mg 2.9 Cd 0.1 AlCl-LDH in NaCl solution (0.02 mol L−1, pH 5), soil extract, and soil matrix, respectively. The very low leaching of Cd from Cd-containing LDHs indicated the high stability of LDH-sorbed Cd via isomorphic substitution and feasible practical application in Cd sequestration in wastewater treatment and soil remediation. [Display omitted] • Eleven LDHs were synthesized to evaluate Cd sorption performance. • Ca 3 AlCl-LDH shows super high Cd sorption capacity of 625 mg g−1 • Cd-bearing MgAlCl-LDH was fabricated to assess Cd sorption stability. • Low Cd leaching from Mg 2.9 Cd 0.1 Al-LDH was observed ranging from 7.7% to 0.96%. • Isomorphic substitution facilitated Cd sorption and induced super stable products. [ABSTRACT FROM AUTHOR]