Chenghao Lu

Methotrexate-Loaded PEGylated Chitosan Nanoparticles: Synthesis, Characterization, and in Vitro and in Vivo Antitumoral Activity

Cancer nanotherapeutics are rapidly progressing and being implemented to solve several limitations of conventional drug delivery systems. In this paper, we report a novel strategy of preparing methotrexate (MTX) nanoparticles based on chitosan (CS) and methoxypoly(ethylene glycol) (mPEG) used as nanocarriers to enhance their targeting and prolong blood circulation. MTX and mPEG-conjugated CS nanoparticles (NPs) were prepared and evaluated for their targeting efficiency and toxicity in vitro and in vivo. The MTX-mPEG-CS NP size determined by dynamic light scattering was 213 ± 2.0 nm with a narrow particle size distribution, and its loading content (LC %) and encapsulation efficiency (EE) were 44.19 ± 0.64% and 87.65 ± 0.79%, respectively. In vitro release behavior of MTX was investigated. In vivo optical imaging in mice proved that MTX was released from particles subsequently and targeted to tumor tissue, showing significantly prolonged retention and specific selectivity. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay obviously indicated that the higher inhibition efficiency of MTX-mPEG-CS NPs meant that much more MTX was transferred into the tumor cells. A significant right-shift in the flow cytometry (FCM) assay demonstrated that MTX-loaded nanoparticles were far superior to a pure drug in the inhibition of growth and proliferation of Hela cells. These results suggest that MTX-mPEG-CS NPs could be a promising targeting anticancer chemotherapeutic agent, especially for cervical carcinoma.

Effects of Slag Refining on Boron Removal from Metallurgical-Grade Silicon Using Recycled Slag with Active Component

A new slag refining method to remove boron from metallurgical silicon (MG-Si) by mixed reused slag and active component was proposed. The silicon was refined with CaCl2-CaO-SiO2 slag system in this work. The boron removal efficiency under different temperature and holding time was investigated, particularly for the recycle of the used slag mixed with different amount of CaCl2 in the 2nd and the 3rd run. The multiple slag refining was adopted to test the effect of reused slag; the boron removal ratio was 96% and 94% at 1923 K and 1873 K, respectively. These methods could significantly reduce the slag amount in refining. The total transfer coefficient of boron was also derived by the boron content. The overall boron removal mechanism and effect of slag recycle on boron removal was also discussed.

Separation of Metal Impurities from Metallurgical Grade Silicon via CaO-SiO2-CaF2 Slag Treatment Followed by Leaching with Hydrochloric Acid

The separation of metal impurities from metallurgical grade silicon by a combination of slag treatment and acid leaching was investigated. Based on a detailed analysis of microstructure evolution in metallurgical grade silicon, the primary precipitated phase in silicon was tended to form Si-Ca system intermetallics after CaO-SiO2-CaF2 slag treatment. Moreover, the extraction efficiency of metal impurities from silicon with slag treatment was higher than that without slag treatment in the leaching process. Some parameters such as acid concentration, temperature, particle size, stirring speed and leaching time were also discussed. The extraction of impurities Fe, Al and Ca increased with increasing acid concentration, leaching time and decreasing particle size. Besides, the leaching kinetics of these metal impurities was confirmed to be controlled by chemical reaction with the application of cracking shrinking model.

Effect of solidification rate on representative impurities distribution in Si-Cu alloy

Abstract The main purpose of this article is to demonstrate that solvent refining in combination with directional solidification can be used for preparation of high purity metallurgical grade silicon for solar cells. Silicon was alloyed with copper and grew under different solidification rates from Si–Cu alloy melt. A detailed analysis of the microstructures and morphologies of Si–Cu alloy has been carried out, focusing on the distribution characteristic of representative impurities affected by solidification rate. The experimental results indicated that copper addition promotes segregation of metal impurities Fe, Al and Ca from metallurgical grade silicon, and the purification effect is more pronounced with the solidification rate decreases. It was also determined that the representative non-metallic impurity phosphorus has a remarkable separation performance after alloying with copper, which can be helpful for the phosphorus removal.

Effect of Na2O-SiO2 slag treatment on hydrometallurgical purification of metallurgical grade silicon

The effects of Na2O-SiO2 slag treatment on purification of metallurgical grade silicon by leaching with hydrogen fluoride have been investigated. A comparative analysis of microstructure evolution was carried out to examine the leaching behavior of impurities from metallurgical grade silicon. It was found that the distribution of metal impurities Al, Ca, Ti and Na, which co-deposited with Si and formed different intermetallic phases at grain boundaries, had manifest distinction between precipitated phase and silicon. Moreover, acid corrosion experiment results revealed that slag treatment improved the dissolution rate of metal impurities from metallurgical grade silicon as contrasted to that without slag treatment.

Research on the whitening mechanism of kaolin by chemical bleaching and calcining

Bleaching and calcining are the major whitening process in kaolin industry. However, the whitening mechanism has not been clarified yet. In this paper, the whitening mechanism of kaolin was investigated. Kaolin was bleached with hydrosulfite and calcined under different temperature separately, the whiteness and microstructure were detected throughly by X-ray diffraction and scanning electron microscope. The soluble and insoluble Fe content were determined by phenanthroline spectrophotometry. Effect of chemical bleaching, calcined temperature on mineral characteristics and whiteness was discussed. The mechanism of whitening was analyzed systematically.

Boron removal from metallurgical-grade silicon by slag refining with Yttria-silica system

A new slag system, Y2O3-SiO2-CaF2 system, was adopted in purification of Si for photovoltaic application. The partition ratio of boron (LB) between slag and silicon was studied under different mass ratio of slag to silicon and varying basicity at 1873K. Scanning electron scope and electron probe micro analysis were used to detect the distribution of impurity elements in silicon after slag refining. The experimental results show that the mass ratio of slag to silicon did not affect the trend of slag basicity with LB, and high mass ratio of slag to silicon would decrease LB. Silicon was surrounded by amorphous slag. Impurity elements are concentrated in slag. Yttrium oxide’s role in slag and kinetic analysis of boron removal are also discussed.