RESUMO
This study utilizes desalted and denitrated treated aluminum dross (TAD) as a raw material, along with kaolin and 10 ppi (pores per inch) polyurethane foam as a template. The slurry is converted into an aluminum dross green body with a three-dimensional network structure using the impregnation method. A three-dimensional network aluminum dross ceramic framework (TAD3D) is created at a sintering temperature of 1350 °C. The liquid 5A05 aluminum alloy at a temperature of 950 °C infiltrates into the voids of TAD3D through pressureless infiltration, resulting in TAD3D/5A05Al composite material with an interpenetrating phase composite (IPC) structure. The corrosion behavior of TAD3D/5A05 composite material in sodium chloride solution was examined using the salt spray test (NSS) method. The study shows that the pores of the TAD3D framework, produced by sintering aluminum dross as raw material, are approximately 10 ppi. The bonding between TAD3D and 5A05Al interfaces is dense, with strong interfacial adhesion. The NSS corrosion time ranged from 24 h to 360 h, during which the composite material underwent pitting corrosion, crevice corrosion and self-healing processes. Results from Potentiodynamic Polarization (PDP) and Electrochemical Impedance Spectroscopy (EIS) indicate that, as corrosion progresses, the Ecorr of TAD3D/5A05Al decreases from -0.718 V to -0.786 V, and Icorr decreases from 0.398 µA·cm-2 to 0.141 µA·cm-2. A dense oxide film forms on the surface of the composite material, increasing the anodic Tafel slope and decreasing the cathodic Tafel slope, thus slowing down the rates of cathodic and anodic reactions. Factors such as lower interface corrosion resistance or a relatively weak passivation film at the interface do not significantly diminish the corrosion resistance of TAD3D and 5A05Al. The corrosion resistance of the composite material initially decreases and then increases.
RESUMO
Aluminum dross is a well-known industrial waste generated in the aluminium industry, and its recycling and reuse is still a worldwide issue. Herein, aluminum dross waste (ADW) was recycled to progressively replace the aggregate fraction of clay at 70, 75, 80, 85, and 90 wt% for the fabrication of Al2O3-SiO2-rich porous castable refractories. Their physical properties and mechanical behavior were assessed by the measurement of linear shrinkage rate, bulk density, apparent porosity, cold crushing strength, and thermal conductivity. The microstructure and phase evolutions were analyzed via scanning electron microscopy (SEM) and X-ray diffraction (XRD). The incorporation of 85 wt% of ADW allowed the development of a waste-containing conventional refractory castable with improved properties as compared to those of the other samples. The sustainable refractory castable exhibited decent thermal conductivity and physical and mechanical characteristics, and is suitable for application as reheating furnace lining. It is a "green" practice to partially replace the traditional raw materials with industrial waste in the manufacture of conventional refractory castables and provides environmental and economic benefits.
RESUMO
Clay liners play a critical role in preventing leachate leakage and pollutant migration from landfills through their low permeability and non-Darcy behavior during seepage, and such liners exhibit a threshold-gradient characteristic. Landfill waste may produce complex, highly concentrated leachates through chemical and biological degradation. The hydraulic conductivity and threshold gradient of a clay liner is affected by high leachate concentrations. Some scholars have suggested that chemical oxygen demand (COD) can be selected as a key indicator for pollution alerts and used to assess the environmental risk posed by municipal solid waste (MSW) landfill sites. To study the influence of leachate concentration on the permeability of compacted clay, the highest concentrations of organic pollutant COD (glucose configuration) were used as the target dialysate in this study. COD is abbreviation of chemical oxygen demand. A COD solution was prepared from dissolved glucose for the experiments. The results showed that as the COD concentration increased, the hydraulic conductivity increased and the threshold gradient decreased. The permeate viscosity and the soil-water characteristic curve were measured. As the COD concentration increased, the permeate viscosity increased and the bound water content decreased. By considering the COD concentration effects on permeate viscosity and intrinsic permeability and adapting a previously established empirical relationship between the threshold gradient and apparent fluidity (K/η), this study derived an equation for calculating the hydraulic conductivity and threshold gradient with changes in the COD concentration, and good predictions were obtained.
