[Effect of three mixing methods on air bubbles and solidification state of alginate impression materials].

PURPOSE: To evaluate the effect of full-automatic mixing machine method, clockwise manual mixing and combined eight-shaped manual mixing on air bubble content, flowability, temperature, working time and setting time of alginate impression materials. METHODS: With the same condition, alginate impression materials were mixed by three different methods. The number of bubbles, area, flowability, temperature, working time and setting time were evaluated with SPSS 24.0 software package. RESULTS: The number of bubbles in the automatic mixing group was (2.30±2.50), and the area was (0.17±0.18) mm2, which was less than the number of clockwise manual mixing group (59.60±14.19), and the total area (7.41±2.24) mm2 (P＜0.01). The flowability of the clockwise manual mixing group [(39.52±0.85) mm] was less than that of the full-automatic mixing group [(50.78±0.90) mm] and the combined eight-character manual mixing group [(50.36±1.75) mm](P＜0.01).The setting time of the material mixed by three methods was eligible for clinical use. CONCLUSIONS: The mixing method of alginate impression material has an effect on material's bubble content, flowability and temperature changes. The impression materials mixed by full-automatic mixing method are better in terms of bubble content, flowability and other properties. If manual mixing is used, combined eight-shaped manual mixing method can help reduce impression bubbles and deformation, and improve flowability.

Removing BaP from soil by biochar prepared with medicago and corn straw using batch and solid-phase extraction method.

Low-cost materials with a highly efficient adsorption capability prepared from corn straw and medicago (abbreviated to CB and MB), which can effectively remove benzo(a)pyrene (BaP) from contaminated soil, were prepared at a temperature of 350 °C under limited-oxygen conditions. The appearance traits, contents of C, H, N and functional group types of CB and MB were obtained by SEM, elemental analysis and FT-IR. Through the batch method, it was found that the adsorption of BaP by CB and MB was in accordance with pseudo-secondary kinetics because the correlation coefficients are 0.855 with CB and 0.948 with MB, respectively, and the maximum adsorption capacity in the fitting (CB: 78.2 mg kg-1, MB: 88.8 mg kg-1) was consistent with the actual measurement (CB: 79.8 mg kg-1, MB: 89.3 mg kg-1). Freundlich and Langmuir equations can well describe the isothermal adsorption data of CB and MB due to the correlation coefficients all being greater than 0.87. Soil samples treated with ASE were separated by solid-phase extraction (SPE) with different biochar contents in packed columns. It was found that the contributions of CB and MB to the removal of BaP increased from 58.5% and 60.4% to 80.6% and 82.1%, respectively, which could effectively reduce BaP in polluted soil.