Preparation of Cationic CMP and Softwood Long Fibers as Strength-Enhancing Additive to CMP Pulp
Compared to chemical pulp, mechanical and chemi-mechanical pulps (CMP) are limited in regards to the manufacturing of high quality paper. Chemical additives are an effective way to enhance the properties of paper; however, the effectiveness depends on the additive type and dosage. The utilization of cationized natural polymers has been shown to offer a promising solution. In this study, softwood long fiber (SLF) and CMP were cationized by 3-chloro-2-hydroxypropyl-trimethylammonium-chloride (CHPTAC), and the effects of cationization on the properties of CMP pulp were studied. Cationization was characterized by FTIR and the nitrogen content, and its effect on the CMP properties was evaluated through mechanical tests and fines retention. Cationization at low and moderate levels and in higher mixing rates improved the mechanical properties of CMP. Compared to cationized CMP, the addition of cationized SLF (CLF) improved the strength and fines retention properties. The CLF application to CMP at a CHPTAC dosage of 5% increased the tensile, burst, and tear strengths by 66.4%, 100%, and 3.6%, respectively. The cationized SLF increased the fines retention by 12.7%.
Novel Retention System Based on (2,3-Epoxypropyl)trimethylammonium Chloride Modified Silica Nanoparticles and Anionic Polymer
This work investigated the synthesis, characterization, and evaluation of surface-modified cationic silica nanoparticles as part of retention or flocculation systems. Quaternary amine groups were introduced onto the fumed silica surface using the cationic reagent (2,3-epoxypropyl)trimethylammonium chloride under various reaction conditions. To characterize the surface properties of the modified silica particles, the ζ potential and charge density were determined. Dynamic flocculation experiments showed that, when used alone, the cationic silica nanoparticles contributed little to inducing clay flocculation. However, when the nanoparticles were used in conjunction with an anionic polymer of high Mw and low charge density, significant improvement in the flocculation of fine clay particles was achieved. The interaction between the cationic silica nanoparticles and anionic polymer, as well as the silica adsorption behavior on clay surfaces, was explored. The mechanism of flocculation induced by the dual-compo...
Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal
The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 mol/L H2SO4 at 90°C for 2 h. After the sample is roasted at 900°C for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the content of V(V) increases with the rise of roasting temperature from 600 to 900°C, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000°C. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.