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A B S T R A C TCeO 2 and TiO 2 engineered nanoparticles (ENPs) are being increasingly used in many applications. Due to their properties, heteroaggregation between these two types of ENPs is very likely, which can determine their fate and transport. However, the heteroaggregation behavior of CeO 2 and TiO 2 ENPs is still not clear, partly due to the lack of appropriate tools. In this study, we investigated the application of Turbiscan Stability Index (TSI) for the measurements of CeO 2 /TiO 2 ENP heteroaggregation. TSI was found to be effective to investigate the heteroaggregation and stability of the CeO 2 -TiO 2 ENPs system. Increasing CeO 2 /TiO 2 ENPs ratio reduces the TSI values, indicating higher stability. Fluorescence excitation-emission matrix (EEM) spectra were used to study the interface interaction between humic acid (HA) and CeO 2 /TiO 2 ENPs. The TSI value of ENPs were rising with the increasing of CeO 2 /TiO 2 ENPs ratios in the H River or Q Reservoir water. In addition, their variation trends were http://dx

At present, the dealkalization and comprehensive utilization of red mud is a worldwide problem. Studies on the settling performance and phase transformation of red mud by HCl, CaO, and HO leaching are limited. In this study, the characteristics of red mud were systematically analyzed. The average sizes of graded and initial red mud were 4.11 and 9.20 μm, respectively. X-ray diffraction (XRD), X-ray fluorescence spectra (XRF), and thermogravimetry-differential scanning calorimetry (TG-DSC) results indicated the different mineralogical phases, composition, and thermal behavior. The addition of HCl could neutralize the alkalization in the red mud slurry, and CaO could replace the Na and K. Notably, the pH of the red mud slurry had no obvious change with the increase in water washing times in a certain pH. Interestingly, soluble Al and Fe were not detected in the HCl-red mud and CaO-red mud. In addition, the settling ratio was used to express the settling performance of the red mud slurry. Their interaction mechanisms were proposed, which may include phase transformation and the changing of the size and surface area. The research provided a better understanding of the phase transformation and settling performance in the treatment of red mud by HCl, CaO, and HO leaching.