High-Grade Ferronickel Concentrates Prepared from Laterite Nickel Ore by a Carbothermal Reduction and Magnetic Separation Method.

Nickel is widely used in industrial processes and plays a crucial role in many applications. However, most of the nickel resource mainly exists as nickel oxide in laterite nickel ore with complex composition, resulting in difficulty in upgrading the nickel content using physical separation methods. In this study, high-grade ferronickel concentrates were obtained through a carbothermal reduction and magnetic separation using laterite nickel ore and anthracite as raw materials. The effects of different types of additives (CaF2, Na2SO4, and H3BO3), carbon ratio (the molar ratio of oxygen atoms in the laterite nickel ore to carbon atoms in anthracite), and grinding time on the recoveries and grades of ferronickel concentrates were experimentally investigated, along with the microstructure and chemical composition of the products. CaF2 was proved to be the primary active additive in the aggregation and growth of the ferronickel particles and the improvement of the grade of the product. Under the optimal conditions of CaF2 addition of 9.85 wt%, carbon ratio of 1.4, and grinding time of 240 s, high-grade magnetically separable ferronickel concentrate with nickel grade 8.93 wt% and iron grade 63.96 wt% was successfully prepared. This work presents a practical method for the highly efficient recovery and utilization of iron and nickel from low-grade laterite nickel ore, contributing to the development of strategies for the sustainable extraction and utilization of nickel resources.

A novel insight into the microwave induced catalytic reduction mechanism in aqueous Cr(VI) removal over ZnFe2O4 catalyst.

Aqueous Cr(VI) pollution is an emerging environmental issue. Herein, a sphere-like ZnFe2O4 catalyst with a size of ∼430 nm was prepared by a solvothermal method, by which the aqueous Cr(VI) in a 50 mL solution with concentration of 50 mg/L was completely removed after 10 min-microwave (MW) irradiation. "Surface temperature visualization" tests and COMSOL simulations showed that the surface temperature of the as-prepared ZnFe2O4 catalysts could be as high as > 1000 °C only after 300 s MW irradiation, and the work function calculations and scavenging experiments demonstrated that the excited electrons derived by the "hot spots" effect of the ZnFe2O4 catalysts reduced the Cr(VI) to Cr(III). Kinetic reaction process of the reduction of *Cr2O72- to *CrO3H3 over the ZnFe2O4 catalysts was clarified by using DFT calculation, and the results indicated that *Cr2O72- adsorbed on the Fe atoms was more easily to be reduced, and that Fe atoms played more significant roles than the Zn and O atoms in ZnFe2O4 catalysts. The present study not only proves that the MW induced ZnFe2O4 catalytic reduction was promising for ultrafast remediation of toxic Cr(VI), but also provides a new insight into the corresponding mechanism.

A robust air superhydrophilic/superoleophobic diatomite porous ceramic for high-performance continuous separation of oil-in-water emulsion.

Three-dimensional (3D) porous architecture has attracted considerable attention in remediation of oil/water emulsion. In present work, an air superhydrophilic/superoleophobic diatomite porous ceramic (AS-DC) was prepared, using SiO2 whiskers modified diatomite ceramic as the substrate and FS-50 as the modifier. The interconnected SiO2 whiskers intertwined on the skeleton of ceramic block forming a 3D network structure, which not only improved the wettability of AS-DC, but also reinforced its mechanical property (about 2.5 MPa of compressive strength). The as-prepared AS-DC with intrinsically superoleophobicity (154°) and superhydrophilicity (0°) exhibited an underwater oil contact angle of 161°, suggesting a multifunctional separation capability. By simply assembling AS-DC with pipes and a pump, it could not only separate the surfactant-stabilized oil-in-water emulsion in a permeation flux as high as 107.8 kg min-1 m-2 with a selectivity of >95%, but also collect the clean water from the floating oil/water mixture in a flux of 197.4 kg min-1 m-2 and a selectivity of ∼99%. In addition, the AS-DC was resistant to the salt/acid/alkaline corrosion and temperature fluctuation. The mechanical/chemical firmness of AS-DC renders it tremendous potential as a robust 3D architecture in real application for purification of oil/water mixture.

Joule-heatable bird-nest-bioinspired/carbon nanotubes-modified sepiolite porous ceramics: An efficient, sturdy, and continuous strategy for oil recovery.

Oil-spill accident is a severe globally concerned environmental issue. In this work, a Joule-heatable bird-nest-bioinspired/carbon nanotubes-modified sepiolite porous ceramic (JBN/CM-SC) was developed, using inexpensive sepiolite porous ceramics as the substrate and carbon nanotubes (CNTs) derived from waste plastics as the modifier. The former exhibited outstanding mechanical property (1.7 MPa of compressive strength), gas permeability (9.1 × 10-11 m2), thermal conductivity (0.215 W·m-1·K-1) and thermal/chemical stability. As expected, the deposited CNTs not only conferred a hydrophobic surface, but also resulted in a Joule-heating ability of intrinsically non-conductive ceramics. As-prepared JBN/CM-SC demonstrated a separation rate as high as 120-200 kg·s-1·m-2 for oil recovery and a high selectivity of over 95%. The Joule heat generated by the heated JBN/CM-SC could in-situ reduce the oil-viscosity, remarkably increasing the oil-diffusion. The separation rate was enhanced by ~12 times with respect to that of the non-heated counterpart. In addition, the idea of modular design was proposed. By simply combining JBN/CM-SC components with pipes and a pump, a continuous in-situ collection of oil from an oil/water mixture was realized, providing an efficient, sturdy, and continuous approach to recover the spilled oil in an oil-spill accident.