Search Results (3)

This study investigated the effects of washing equipment for inorganic salts, such as NaCl, KCl, and CaClOH, to decontaminate municipal solid waste incineration fly ash (MSW-IFA). Based on the feature of hydrodynamic cavitation, the device developed in this study (referred to as a ‘washing ejector’) utilizes the cavitation bubbles. A washing ejector was analyzed under a range of conditions, employing as little water as possible. In hydrodynamic cavitation, the increase in fluid pressure with increasing static pressure is mainly attributed to the increase in particle–bubble collisions via the cavitation flow. The results revealed that the fluid pressure influenced the removal of inorganic salts during cavitation in water. This is because during the washing process from the collapse of cavitation bubbles, the release is achieved through the dissolution of inorganic salts weakly bound to the surface. After treatment by a washing ejector, the removal of soluble salts elements such as Cl, Na, and K was reduced by approximately 90%. Removing the inorganic salts in the IFA altered the characteristics of the Ca-related phase, and amorphous CaCO₃ was formed as the cavitation flow reacted with CO₂ in the ambient air. Furthermore, the washing effluent produced by washing IFA was found to be beneficial for CO₂ capture. The washing effluent was enriched with dissolved Ca from the IFA, and the initial pH was the most favorable condition for the formation of CaCO₃; thus, the effluent was sufficient for use as a CO₂ sequestration medium and substitute for the reuse of water. Overall, the process presented herein could be effective for removing soluble salts from IFA, and this process is conducive to utilizing IFA as a resource. Full article

Based on the features of hydrodynamic cavitation, in this study, we developed a washing ejector that utilizes a high-pressure water jet. The cavitating flow was utilized to remove fine particles from contaminated soil. The volume of the contaminants and total metal concentration could be correlated to the fine-particle distribution in the contaminated soil. These particles can combine with a variety of pollutants. In this study, physical separation and soil washing as a two-step soil remediation strategy were performed to remediate contaminated soils from the smelter. A washing ejector was employed for physical separation, whereas phosphoric acid was used as the washing agent. The particles containing toxic heavy metals were composed of metal phase encapsulated in phyllosilicates, and metal phase weakly bound to phyllosilicate surfaces. The washing ejector involves the removal of fine particles bound to coarse particles and the dispersion of soil aggregates. From these results we determined that physical separation using a washing ejector was effective for the treatment of contaminated soil. Phosphoric acid (H₃PO₄) was effective in extracting arsenic from contaminated soil in which arsenic was associated with amorphous iron oxides. Thus, the obtained results can provide useful information and technical support for field soil washing for the remediation of soil contaminated by toxic heavy metals through emissions from the mining and ore processing industries. Full article

A washing ejector is a pre-treatment technology used to remediate contaminated soil by separating fine particles. The washing ejector developed in this study is a device that utilizes fast liquid jets to disperse soil aggregates by cavitation flow. The cavitation phenomenon is affected by the Bernoulli principle, and the liquid pressure decreases with the increase in kinetic energy. The cavitating flow of the fluid through the Ventrui nozzle can remove surface functional groups and discrete particles. The main methodology involves the removal of small particles bound to coarse particles and the dispersion of soil aggregates. Particle collisions occur on the surface soil, such as the metal phase that is weakly bound to silicate minerals. It was observed that the dispersed soil affected the binding of toxic heavy metals and the mineralogical characteristics of the soil. The quantity of oxides, organic matter, and clay minerals affected the properties of the soil. An almost 40–60% removal efficiency of total metals (As, Zn, and Pb) was obtained from the contaminated soils. After treatment by a washing ejector, the volume of fine particles was reduced by 28–47%. When the contaminants are associated with particulates, separation using a washing ejector can be more effective. Therefore, physical separation improves the removal efficiency of heavy metals from soil aggregates. Full article