Role of polyurethane-modified layered double hydroxides on SCFAs extraction from waste activated sludge fermentation liquid for elevating denitrification: Kinetics and mechanism.

Extraction of short-chain fatty acids (SCFAs) from fermentation liquid of waste activated sludge (WAS) is the key bottleneck hindering its application as electron donor in denitrification. This study explores the feasibility of polyether-type polyurethane (PU)-modified layered double hydroxides (LDHs, prepared using eggshell waste as calcium source) in SCFAs adsorbing from WAS fermentation liquid (SFL). The adsorption parameters were first optimized by adsorption tests using artificial fermentation liquid (AFL). Then, adsorption kinetics, thermodynamic and isotherms were explored to further understand the adsorption mechanism. It revealed that SCFAs absorption by PU-LDHs from SFL was an endothermic and spontaneous process with positive enthalphy (ΔH◦) values and negative Gibbs free energy (ΔG◦) values. In addition, the maximum adsorption capacity of 208.0 mg SCFAs/g PU-LDHs was obtained from the Langmuir isotherm. Noting that both soluble carbohydrates and soluble proteins were simultaneously extracted, with efficiencies of 30.9%, 6.2%, respectively, compared with 62.9% SCFAs. The reuse tests confirmed that the prepared PU-LDHs can be used at least three times with high adsorptive capacity. With PU-LDHs-loaded SFL as external carbon source in the biodenitrification process, a denitrification rate of 0.014 mg NO3--N/mg mixed liquid suspended solids (MLSS)·d was recorded. This study provided a sound basis for the preparation of cost-effective biodenitrification carbon source from SFL by a novel adsorbent.

[Stability of the anterior teeth and hard tissue of skeletal class III malocclusion after orthodontic surgery: systematic review].

OBJECTIVE: This study aims to analyze the long-term stability of the anterior teeth and hard tissue of skeletal class III malocclusion after a three-year orthodontic surgery by systematic review. METHODS: All studies about skeletal class III malocclusion with orthodontic-surgery were searched by computer-based retrieval and manual retrieval; the deadline is December 2013. The literature, filtered according to the inclusion criteria and exclusion criteria, was performed with quality. assessment. The same indicators of the anterior location and hard tissue stability were combined and evaluated with metaanalysis and descriptive analysis by Rev Man5.2. RESULTS: Four before-and-after comparison study articles with 180 cases were included. The grades of the four literature evaluation were A. The meta-analysis results showed that comparing the three-year post-orthodontic-surgery and post-orthodontic-surgery, the total weighted mean difference (WMD) of Ul-SN was 4.29 (P<0.05); the WMD of Ll-MP, OB, OJ, SNA, SNB, ANB, and MP-SN were -1.58, 0, -0.41, -0.58, 0.25, -0.70, and 0.39, respectively (P>0.05). The measurement methods of A and B point position were different, hence the qualitative description were as follows: point A remained at a relatively stable position, and point B had some replacement compared with post-operative (P<0.05). CONCLUSION: To the skeletal class III malocclusion after three-year orthodontic-surgery, the position of the lower anterior teeth could be kept stable, as well as the overbite and the overjet of the anterior teeth; only the upper inci- sor has a lip-inclined relapse. The maxillary could also be kept stable, and the mandibular had a little relapse.