Chitosan-modified magnetic carbon nanomaterials with high efficiency, controlled motility, and reusability-for removal of chromium ions from real wastewater.

Hexavalent chromium Cr(VI) is one of the most hazardous oxygen-containing anions to human health and the environment. Adsorption is considered to be an effective method for the removal of Cr(VI) from aqueous solutions. Based on an environmental perspective, we used renewable biomass cellulose as carbon source and chitosan as functional material to synthesize chitosan-coated magnetic carbon (MC@CS) material. The synthesized chitosan magnetic carbons were uniform in diameter (~ 20 nm) and contain a large number of abundant hydroxyl and amino functional groups on the surface, meanwhile owning excellent magnetic separation properties. The MC@CS exhibited high adsorption capacity (83.40 mg/g) at pH 3 and excellent cycling regeneration ability when applied to Cr(VI) removal in water, removal rate of Cr(VI) (10 mg/L) was still over 70% after 10 cycles. FT-IR and XPS spectra showed that electrostatic interaction and reduction with Cr(VI) are the main mechanisms of Cr(VI) removal by MC@CS nanomaterial. This work provides an environment-friendly adsorption material that could be reused for the removal of Cr(VI) in multiple cycles.

Synthesis and influencing factors of high-performance concrete based on copper tailings for efficient solidification of heavy metals.

Copper tailings containing a large amount of heavy metals such as Pb, Cu, As, Mn, and Cr discharged from its mining are a typical bulk solid waste, which is highly hazardous to human and the environment. This research proposed a sustainable and effective method for the environmentally sound utilization of copper tailings solid waste. A high-strength concrete material with copper tailings as the main raw material was successfully prepared, with a 28-day compressive strength of up to 85.35 MPa, the flexural strength reached 12.46 MPa, and the tailings utilization rate of 60%. The mechanical properties and heavy metal stabilization properties of the prepared high-performance concrete were obtained by adding coarse aggregates such as river sand, while changing the sand rate, cementitious material admixture and water-cement ratio. A long-term leaching experiment of the high-strength concrete material with 190 day was carried and proved that the material can be made with low or no risk of heavy metal contamination in copper tailings. Incorporation of copper tailings into the high-performance concrete hydration mainly contains three mechanisms: (i) Pore sealing effect generated by the formation of tailings geopolymer prompted the hardening of the geopolymer layer to form a monolithic package structure; (ii) The active SiO2 material in copper tailings reacts with Ca(OH)2 in the hydration products to produce a strong volcanic ash effect; (iii) the primary hydration of 3CaO·SiO2(C3S) and 3CaO·Al2O3(C3A) in the cement, and the secondary hydration reaction induced by the copper tailings and silica fume. These mechanisms are blended with each other to form a dense microstructure of the slurry, which embodies extremely high mechanical properties on a macroscopic scale, providing a reference role for the bulk utilization of copper tailings.

Degradation mechanism of HCN by electrochemically coupled copper-loaded magnetic nanoparticles in a liquid phase pseudo-homogeneous system.

Hydrogen cyanide (HCN) comes from a wide range of sources, but it is highly toxic and corrosive, harming the environment and human health. This experiment used magnetic nano-Fe3O4 particles loaded with Cu (Cu-Fe3O4 magnetic nanoparticles) for electrochemical catalytic purification of HCN in a liquid phase pseudo-homogeneous system. The results show that the purification efficiency of Cu-Fe3O4 magnetic nanoparticles on HCN is 70% without electricity. After a certain voltage is applied, the degradation efficiency of 2 h with iron-carbon particles is significantly improved, and the degradation efficiency can reach about 95%. And the degradation efficiency increases with the increase of voltage. The electrochemical synergistic degradation mechanism of Cu-Fe3O4 magnetic nanoparticles is complex, which can directly catalyze the degradation of HCN or form CNO- intermediates to further degrade into CO2, H2O, and NH3. Meanwhile, Fe2+, Cu+, and other transition metal ions in the liquid phase participate in the Fenton-like reaction to further degrade HCN. The results show that the synergistic electrochemical degradation of HCN by Cu-Fe3O4 magnetic nanoparticles has excellent potential to degrade highly toxic gases.

Efficient purification of hydrogen cyanide by synergistic effects of electrochemical and liquid phase catalysis.

In this study, Co, Cu, Pd, and Pd/Cu composite metal ions were used to synthesize metal nanoparticles with high efficiency in purifying hydrogen cyanide gas. The pure liquid phase catalytic purification of hydrogen cyanide gas was studied. According to the removal rate, the Pd/Cu composite metal ions had the best purification efficiency among the nanoparticles of different metal types. The removal rate order was Pd/Cu>Pd>Cu>Co. The gas after reaction were analyzed by gas chromatography, and it was found that HCN was converted into CO2, N2 and NH3 by nanoparticles. Then, Pd/Cu composite metal ions with the highest purification efficiency were used to study the electrochemical synergistic liquid-phase catalytic purification of HCN gas. The effects of electrochemical conditions and current on the electro-hydraulic synergistic purification were studied. The removal efficiency of HCN by electrochemical synergistic liquid phase catalysis was better than that by pure liquid phase catalysis. The different nanoparticles before and after HCN absorption were characterized and analyzed to explore the purification process of HCN. The purification mechanism of hydrogen cyanide by Pd-Cu catalyst under applied voltage was studied under certain conditions. During the catalytic reaction, the nano-catalyst was partially dissolved in liquid phase and partially HCN reacts with metal ions on the free or nanoparticles to form complex [Mc(CN)n]2-n. Homogeneous and quasi-homogeneous reactions in liquid phase interweave together to form a more complex reaction system.