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Dissolution kinetics of hemimorphite in methane sulfonic acid

100%

Zhang Q. , Wen S. , Feng Q. , Nie W. , Wu D.

tom Vol. 55, iss. 1

1--9

Hemimorphite has a large content of zinc, but its recovery using flotation alone is low. Nowadays, hydrometallurgical and pyrometallurgical methods are used to treat zinc ores. In this work, the leaching and dissolution kinetics of hemimorphite by using methane sulfonic acid (MSA) as an alternative leaching reagent was investigated. The effects of several experimental parameters including reaction temperature, MSA concentration, particle size, and stirring speed were also analyzed. Results showed that zinc leaching increased with increased reaction temperature, MSA concentration, and stirring speed, as well as decreased particle size. The mechanism of hemimorphite dissolution in MSA solutions may be a new variant of the shrinking-core model. Based on experimental data and kinetics, the apparent activation energy was determined to be 49.50 kJ/mol. The rate of reaction equation was also obtained to describe the process and found that the MSA concentration largely influenced the leaching of hemimorphite.

Comparison of packing media on stratified EPS and their role in the biofilm of trickling biofilter

86%

Dong B. , Zheng J. , Wen Y.-Z. , Lei X.-Y. , Zhang Q. , Cao D.-J.

2021

tom Vol. 47, nr 3

25--36

The research focused on such packing media as ceramsite, polypropylene balls, and elastic fillers, and analyzed the main characteristics of extracellular polymeric substances (EPS) in their filter biofilms. The EPS were categorized as soluble EPS (S-EPS) and bound EPS (B-EPS). The component characteristics of stratified EPS were investigated via UV-Vis spectroscopy and a three-dimensional excitation-emission matrix (3D-EEM). The results showed that the EPS content of ceramsite biofilm was 245.2 mg/g VSS, which was higher than those of elastic filler material and polypropylene ball by 1.26 and 1.51 times, respectively. The protein (PN) and polysaccharide (PS) ratio of EPS in the ceramsite filter material was highest in S-EPS and B-EPS, indicating that the EPS have a stable structure. More than 67.58% of EPS formed by ceramsite was tightly bound EPS (TB-EPS), which was beneficial to maintaining the stability of biofilms. The levels of proteins (PN) and humic substances formed by ceramsite contained in the TB-EPS were higher than those of elastic filter material and polypropylene balls. 3D-EEM fluorescence spectra revealed that TB-EPS formed by a ceramsite contained high concentrations of tryptophan, tyrosine, and humic substances. The dehydrogenase activity of biofilm formed by ceramsite filler was higher than that formed by elastic fillers and polypropylene balls.

Hydroxyl Terminated Polybutadiene: Chemical Modification and Application of these Modifiers in Propellants and Explosives

72%

Zhang Q. , Shu Y. , Liu N. , Lu X. , Shu Y. , Wang X. , Mo H. , Xu M.

2019

tom Vol. 16, no. 2

153--183

Hydroxyl terminated polybutadiene (HTPB) as a telechelic liquid polymer has been widely used in propellants and explosives and many modified-HTPBs have been reported in the literature. As a binder or additive in propellants and explosives, the chemical modification of HTPB for improving certain properties of propellants has been summarized in detail in this article. According to the application drawbacks of HTPB, modified-HTPB can be classified differently. Furthermore, there are polymers that have been modified on their energetic properties, such as GAP-PB-GAP, BAMO-PB-BAMO, AMMO-PB-AMMO, Nitro-HTPB, HTPB-DNB and NHTPB. Pre-polymers modified on their combustion properties include Butacene®, FPDS-g-HTPB, Fc-HTPB, BiFc-g-HTPB, HTPB→[Fe(CO)3]x, PPA-HTPB-PPA and PNBE-HTPB-PNBE. HTPBs are also modified in curing systems containing, for example ETPB, PTPB, PrTPB, AzTPB, and PUPB, and other modification results are reviewed. Additionally, this overview is expected to provide an outlook for further studies in these fields.