ABSTRACT
In order to deal with the problems of resource waste and environmental pollution caused by solid waste, iron tailings (mainly SiO2, Al2O3 and Fe2O3) were used as the main raw material to create a type of lightweight and high-strength ceramsite. Iron tailings, dolomite (industrial grade, purity 98%) and a small amount of clay were combined in a N2 atmosphere at 1150 °C. X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and a themogravimetric analysis (TGA) were performed and the specific surface area was analyzed to determine the strength and adsorption of the ceramsite. The results of the XRF showed that SiO2, CaO and Al2O3 were the main components of the ceramsite, with MgO and Fe2O3 also included. The results of the XRD and SEM-EDS showed that the ceramsite contained several kinds of minerals and was mainly composed of akermanite, gehlenite and diopside, and that the morphology of the internal structure of the ceramsite was mainly massive and contained a small number of particles. The ceramsite could be used in engineering practice to improve the mechanical properties of materials and meet the requirements of actual engineering for the strength of materials. The results of the specific surface area analysis showed that the inner structure of the ceramsite was compact and that there were no large voids. The voids were mainly medium and large, with a high stability and strong adsorption ability. The TGA results showed that the quality of the ceramsite samples will continue to increase within a certain range. According to the XRD experimental results and experimental conditions, it was speculated that in the part of the ore phase containing Al, Mg or Ca in the ceramsite, the elements underwent relatively complex chemical reactions with each other, resulting in the formation of an ore phase with a higher molecular weight. This research provides the basis of characterization and analysis for the preparation of high-adsorption ceramsite from iron tailings and promotes the high-value utilization of iron tailings for waste pollution control.
ABSTRACT
Cost management and scalable fabrication without sacrificing the purification performance are two critical issues that should be addressed before the practical commercial application of solar-driven evaporators. To address this challenge, we report a porous photothermal hydrogel coating prepared by mixing the raw materials of sawdust (SD), carbon nanotubes (CNTs), and poly(vinyl alcohol) (PVA), which was applied to undergo a blading-drying-rehydration process to prepare the evaporator. In the coating, the crystallized PVA gives the coating a solid skeleton and the sawdust endows the coating with a loose structure to sufficiently enhance the water transportation capacity. As a result, the evaporator coated with the hydrogel coating displays a high water transport rate and efficient evaporation performance along with excellent mechanical properties and stability. Water migrates vertically upward 5 cm within 4 minutes. The compressive stress of the rehydrated hydrogel coating reaches as high as 14.28 MPa under 80% strain. The water evaporation rate of the hydrogel coating-based evaporator reaches 1.833 kg m-2 h-1 corresponding to an energy efficiency of 83.29% under 1 sun irradiation. What is more, the hydrogel coating retains its excellent evaporation performance and stability after immersion in acid or alkali solution, ultrasound treatment, and long-time immersion in water. Under outdoor conditions, the water evaporation rate of the hydrogel coating-based evaporator is about 5.69 times higher than that of pure water. This study proposes a rapid, cost-effective, and scalable strategy for preparing a high-performance photothermal hydrogel coating that will find sustainable and practical application in solar-driven water purification.
