Fabrication of a waste cotton fabrics-based nanosystem for simultaneous removal of Cu(II) and Pb(II).

Herein, a waste cotton fabrics-based nanosystem was fabricated to simultaneously remove copper (Cu(II)) and lead ions (Pb(II)) from water and soil. Therein, carboxyl-functionalized zinc oxide microsphere (ZnO-COOH) with peanut shape was carried by cotton fabric (CF) to get CF/ZnO-COOH nanosystem. CF/ZnO-COOH with a good foldable property possessed a high removal capacity for Cu(II) and Pb(II) via electrostatic attraction and chelation. The result indicated that their removal efficiencies of CF/ZnO-COOH could reach over 95% after 2 h. The adsorption process was consistent with Langmuir (R2 = 0.9905 of Cu(II) and R2 = 0.9846 of Pb(II)) and pseudo-second-order kinetic models (R2 = 0.9999 of Cu(II) and R2 = 0.9999 of Pb(II)). The thermodynamic data showed that the adsorption process was spontaneous and exothermic. Additionally, CF/ZnO-COOH also possessed a high fixation ability for Cu(II) and Pb(II) in sand-soil column, especially for Pb(II) (15 cm, 0.4 µg kg-1). Therefore, this wok provides an environmentally friendly and efficient way to remove Cu(II) and Pb(II) from water and soil concurrently.

Carbon Nanotubes-Based Fuel Cell for Cr(VI) Removal and Electricity Generation.

A fuel cell, an energy transducer, can convert chemical energy into electrical energy. In this work, graphite felt (GF) loaded with polypyrrole (PPy) and carboxylic carbon nanotubes (CNTs-COOH) was used as a cathode (GF/PPy/CNTs-COOH) in a double-chamber nonbiofuel cell (D-nBFC) to remove Cr(VI) efficiently. Therein, Na2S2O3 in an alkaline solution and Cr(VI) in a strongly acidic solution were employed as anode and cathode solutions, respectively. An agar salt bridge, consisting of saturated KCl solution, was used to transport ions between the anode and cathode. This system suggested that the removal efficiency of Cr(VI) could reach 99.6%. The maximum current, power, and power density could achieve 136.8 µA, 18.7 µW, and 20.8 mW/m2 at 90 min, respectively. Additionally, GF/PPy/CNTs-COOH also had good electrocatalytic stability and reusability after four cycles, which played an important role in the development of the D-nBFC system. Therefore, this study provides an environmentally friendly and efficient method to remove Cr(VI) and generate electricity simultaneously.

Tobacco Waste Liquid-Based Organic Fertilizer Particle for Controlled-Release Fulvic Acid and Immobilization of Heavy Metals in Soil.

Every year, a large amount of tobacco waste liquid (TWL) is discharged into the environment, resulting in serious pollution for the environment. In this work, a TWL-based particle (OACT) was fabricated by CaO, attapulgite (ATP), and TWL, and, then, OACT was coated by amino silicon oil (ASO) to form OACT@ASO. Therein, OACT@ASO had high controlled-release ability for fulvic acid (FA), because of the nanonetworks structure for ATP and the high content of FA in TWL. The release ratio (RR) of FA from OACT@ASO reached 94% at 75 h in deionized water, and 23% at 32 d in silica sand. Furthermore, the release mechanism of FA from OACT@ASO was consistent with the First-order law. Additionally, OACT@ASO also possessed high immobilization capacity for Cu(II), Cd(II), and Pb(II) (CCP) in soil. Notably, a pot experiment indicated that OACT@ASO could facilitate the growth of pakchoi seedlings and decrease the absorption of CCP by pakchoi seedlings. Thus, this study provides a new kind of organic fertilizer which could not only release FA, but also immobilize CCP in soil.

Highly Efficient and Simultaneous Removal of Cr(VI) and Imidacloprid through a Ferrocene-Modified MIL-100(Fe) Composite from an Aqueous Solution.

A novel nanocomposite [Fc-MIL-100(Fe)] was constructed by combining ferrocene (Fc) with the porous structural metal-organic framework [MIL-100(Fe)]. The proposed composite material could simultaneously and efficiently remove hexavalent chromium [Cr(VI)] and imidacloprid and reduced strongly noxious Cr(VI) to weakly noxious trivalent chromium [Cr(III)]. The removal efficiencies of the composite material for Cr(VI) and imidacloprid could reach 95% after 15 h. The adsorption process was determined by kinetics, isotherms, and thermodynamics. The results demonstrated that the adsorption kinetics of Cr(VI) followed the pseudo-second-order model mainly by chemisorption; meanwhile, the adsorption of imidacloprid by the material conformed to the pseudo-first-order kinetics, which indicated that physical adsorption was the main process. Additionally, the intraparticle diffusion model revealed that the uptake of imidacloprid and Cr(VI) occurred via intraparticle diffusion at the composite material. The adsorption procedure for Cr(VI) was fitted to the Langmuir model (R2 = 0.995) via monolayer adsorption, and that for imidacloprid was fitted to the Freundlich model (R2 = 0.995) due to multilayer or heterogeneous adsorption. The thermodynamic research confirmed that the adsorption procedure was exothermic and spontaneous. Infrared spectroscopy, X-ray photoelectron spectra, and the pH effect implied that intermolecular hydrogen bonding and electrostatic interaction played a crucial role during the removal process. Fc-MIL-100(Fe) also exhibited long-term stability and satisfactory regeneration and reusability. Therefore, this method may enhance an environmentally friendly and prospective approach for concurrently removing imidacloprid and Cr(VI) from wastewater.

Synthesis of Iron-Based Carbon Microspheres with Tobacco Waste Liquid and Waste Iron Residue for Cd(II) Removal from Water and Soil.

Herein, a novel magnetic iron-based carbon microsphere was prepared by cohydrothermal treatment of tobacco waste liquid (TWL) and waste iron residue (WIR) to form WIR@TWL. After that, WIR@TWL was coated with sodium polyacrylate (S.P.) to fabricate WIR@TWL@SP, whose removal efficiency for bivalent cadmium (Cd(II)) was studied in water and soil. As a result, WIR@TWL@SP possessed a high Cd(II) removal efficiency, which could reach 98.5% within 2 h. The adsorption process was consistent with the pseudo-second-order kinetic model because of the higher value of adjusted R2 (0.99). The thermodynamic data showed that the adsorption process was spontaneous (ΔG° < 0) and exothermic (ΔH° = 32.42 KJ·mol-1 > 0). Cd(II) removal mechanisms also include cation exchange, electrostatic attraction, hydrogen-bond interaction, and cation-π interaction. Notably, pot experiments demonstrated that WIR@TWL@SP could effectively reduce Cd absorption by plants in water and soil. Thus, this study offers an effective method for remediating Cd(II)-contaminated water and soil and may have a practical application value.

A sodium hyposulfite fuel cell for efficient Cr(VI) removal.

This work shows a strategy of reducing hexavalent chromium (Cr(VI)) by sodium hyposulfite (Na2S2O3) with self-generated electricity via a dual-chamber non-biological fuel cell (D-nBFC). Therein, Na2S2O3 was electro-oxidized on graphite felt (GF) at anode and Cr(VI) in strong acidic solution was electro-reduced at GF/CCP cathode (GF decorated with conductive carbon paint (CCP)). Additionally, an agar salt bridge, consisting of saturated KCl solution, was introduced to form complete circuit by offering ions. The results showed that Cr(VI) was reduced to trivalent chromium (Cr(III)) and the D-nBFC system could produce electricity in this process. This system could obtain a high Cr(VI) removal efficiency (97.0%), 110 µA maximum current, and 13.4 mW m-2 maximum power density in 4 h. In addition, the proposed system had high reusability after five cycles and the relative standard deviation was only 3.4% (n = 5). Thus, this D-nBFC system provides a promising and eco-friendly method for treatment of Cr(VI) pollution and generating electricity simultaneously, and also has potential application value for other heavy metals remediation.

Surface migration of Pb(II) from water and soil using an aerogel/graphite felt primary cell system.

To develop a zero energy consumption electrokinetic remediation method of Pb(II) in water and soil, a primary cell system was constructed via synergistic effects of the electromigration, ion exchange, precipitation and hydrogen bond. The primary cell system used cathode of calcium alginate aerogel/graphite felt (CAA/GF) and another piece of CAA/GF was placed on the top of the water and soil. Thus the electric field in the system could drive positively charged Pb(II) towards the top of and thus Pb(II) was surface migrated, promoting removal of Pb(II). This system achieved Pb(II) removal efficiency of 97.8% and maximum power density of 32.1 mW m-2. Additionally, the CAA/GF presented a good reusability. This work provides a promising and facile method to remove heavy metals from water and soil, which might have a huge application prospect.

Fabrication of Fe3O4/ZIF-8 nanocomposite for simultaneous removal of copper and arsenic from water/soil/swine urine.

In this study, a magnetic nanocomposite (denoted as FZ) was fabricated using Fe3O4and zeolitic imidazolate framework-8 (ZIF-8), based on a coprecipitation method. FZ could efficiently remove Cu2+(Cu(II)) and AsO2- (As(III)) ions simultaneously from water, soil, and swine urine samples through hydrogen bonding and electrostatic interactions. The Cu(II) and As(III) removal efficiencies of the optimal FZ sample increased gradually with time and reached 99.1% and 98.4%, respectively, in 180 min. The maximum adsorption capacities of FZ4 for Cu(II) and As(III) were determined to be 33.48 mg/g and 21.12 mg/g, respectively. Additionally, the FZ with a high saturation magnetization (49.8 emu/g) was easily recovered from aqueous solutions and soil samples. Furthermore, zebrafish experiments indicated that FZ possessed a high biosafety. Thus, this study introduces a promising method for treating water, soil, and swine urine samples contaminated with Cu(II) and As(III), and verifies that FZ is suitable for practical application.

Simultaneously removal of Cr(VI) and Cd(II) from water using a flower-like primary battery nanosystem.

In this study, a new flower-like primary battery nanosystem termed "Zn/CCP/ZIF-8" was prepared by depositing conductive carbon paint (CCP) and zeolitic imidazolate framework-8 (ZIF-8) on a zinc plate (Zn). Therein, CCP had good conductivity performance and adhesiveness, ZIF-8 and Zn/CCP/ZIF-8 possessed BET specific surface areas of 1909.5 and 1265.4 m2/g respectively. The results showed that the Zn/CCP/ZIF-8 nanosystem could effectively simultaneously adsorb hexavalent chromium (Cr(VI)) and bivalent cadmium (Cd(II)) from water. The system could promote the transfer of electrons from Zn to Cr(VI) and Cd(II) which were effectively reduced to trivalent chromium (Cr(III)) and cadmium (Cd), respectively. The resultant Zn/CCP/ZIF-8/Cr/Cd composite was then easily separated from water. The adsorption isotherm, kinetics, and thermodynamics of the prepared Zn/CCP/ZIF-8 for Cr(VI) and Cd(II) were investigated. An electrochemistry performance test proved that the Zn/CCP/ZIF-8 system was a primary battery. Notably, the Zn/CCP/ZIF-8 system substantially reduced the amounts of Cr(VI) and Cd(II) absorbed by zebrafish and water spinach, thus increasing food safety. The results of a rat test indicated that the Zn/CCP/ZIF-8 system possessed a high biosafety. This study provides a promising, eco-friendly, and facile method for the simultaneously treatment of Cr(VI) and Cd(II) contamination of water.