Li Jingqiao,Zhang Wenjing,Qin Yunqi,Li Xiaofei,Wu Shengyu,Chai Juanfen,Du Shanghai
To investigate co-transport behavior of ammonium and colloids in saturated porous media under different hydrochemical conditions, NH 4 + was selected as the target contaminant, and silicon and humic acid (HA) were selected as typical organic and inorganic colloids in groundwater. Column experiments were then conducted to investigate the transport of NH 4 + colloids under various hydrochemical conditions. The results showed that because of the different properties of colloidal silicon and HA after combining with NH 4 + , the co-transport mechanism became significantly different. During transport by the NH 4 + –colloid system, colloidal silicon occupied the adsorption sites on the medium surface to promote the transport of NH 4 + , while humic acid (HA) increased the number of adsorption sites of the medium to hinder the transport of NH 4 + . The co-transport of NH 4 + and colloids is closely related to hydrochemical conditions. In the presence of HA, competitive adsorption and morphological changes of HA caused NH 4 + to be more likely to be transported at a higher ionic strength (IS = 0.05 m, CaCl 2 ) and alkalinity (pH = 9.3). In the presence of colloidal silicon, blocking action caused the facilitated transport to be dependent on higher ionic strength and acidity (pH = 4.5), causing the recovery of NH 4 + to improve by 7.99%, 222.25% (stage 1), and 8.63%, respectively. Moreover, transport increases with the colloidal silicon concentrations of 20 mg/L then declines at 40 mg/L, demonstrating that increased concentrations will lead to blocking and particle aggregation, resulting in delayed release in the leaching stage.
Graphical abstract
Dan-Lei Yang,Qian Sun,Hao Niu,Rui-Li Wang,Dan Wang,Jie-Xin Wang
Resin composites have been frequently applied in dental restoration due to their distinguished overall performance. The size, structure and composition of inorganic fillers have significant effects on the properties of dental resin composites (DRCs). The aim of our research is to strengthen the structure of spray-dried silica colloidal nanoparticle clusters (SCNCs) by means of a calcination process, and achieve the excellent comprehensive performance of DRCs by the combined use with different fillers. The results indicate that the SCNCs calcined at 500 °C has a significant strengthening effect on the flexural properties and hardness of DRCs except the decrease of compressive strength in comparison to the uncalcined SCNCs. To overcome this problem, the SiO 2 nanoparticles (NPs) as building blocks for SCNCs and the SCNCs were further adopted as co-fillers of the calcined SCNCs (CSCNCs). It can be found that the strengthening effect of SCNCs is better than that of the NPs at the same filling ratio. The DRCs filled with 60 wt% CSCNCs and 10 wt% SCNCs have a greatly enhanced compressive strength , reaching the same level with the DRCs filled with 70 wt% SCNCs. More importantly, the corresponding flexural strength (143.5 ± 8.3 MPa), flexural modulus (8.91 ± 0.48 GPa) and hardness (70.7 ± 1.4 HV) still have an improvement of 14%, 23% and 48% in comparison with those of the counterpart, respectively.
危险品化学品经营许可证（带存储）