New Insights on Sodium Oleate Adsorption on Quartz for Iron Direct Flotation under Weak-Acidic Condition

To study the sodium oleate (NaOL) adsorption on quartz and its effect on flotation under weak-acidic conditions, the adsorption characteristics of NaOL on the surface of quartz were determined at pH = 6.5 by Fourier transform infrared spectroscopy (FTIR). The solution chemical calculation results show that NaOL exists as oleic acid (HOL) under weakly acidic conditions. The existence form and charge distribution of quartz and HOL were analyzed by Molecular Dynamics Simulation (MDS) using Materials Studio (MS) software, and the results showed that HOL is prone to the (101) and (100) surfaces of quartz under weak-acidic conditions by hydrogen bonding. The flotation verification test with NaOL as a collector was also performed under weak-acidic conditions. The flotation test led to a partial flotation of quartz into the froth products, reducing the grade of hematite direct flotation concentrate, which is consistent with industrial production.

Robust and nanostructured chitosan–silica hybrids for bone repair application

Acetic acid contributes to the strong ionic interaction between Si ions and chitosan by providing a weak acidic condition, and its steric hindrance effect leads to the formation of nanosized silica particles and their homogeneous distribution.

Simultaneous reduction of by-products of chlorine dioxide and chlorine using Fe(II)–Al(III) coagulant mixture

Ferrous iron has been considered very useful for removal of chlorite, a by-product of chlorine dioxide. However, a serious problem can occur associated with high residual iron concentrations in water after Fe(II) treatment, especially at weak acidic condition (pH 6), having a higher capacity of chlorite reduction. Simultaneous removal of chlorite, dissolved iron, and humic acids was achieved with a Fe(II) –Al(III) (1:5) coagulant mixture. Moreover, a significant reduction of chlorine by-products formed after subsequent post chlorination was observed. The by-products of chlorine dioxide and chlorine could be dramatically reduced by the simple addition of the coagulant mixture without the additional problem of dissolved iron.

Improvement of Heartwood Color of Black-Colored Sugi (Cryptomeria japonica D. Don) by UV Irradiation after Smoke Heating

Summary Black-colored heartwood of sugi (Cryptomeria japonica D. Don) logs with bark attached were smoked, heated, and smoke-heated separately to improve the heartwood color. After each treatment, changes of heartwood color, amounts of extracts (hot water, 1 % sodium hydroxide, and ethanol-toluene), metal ions (sodium, potassium, calcium and magnesium), and pH were examined. In addition, changes of heartwood color by UV irradiation (wavelength at 254 nm and 365 nm) also were studied. Heating and smoke-heating of logs prevented blackening of the heartwood, leading to a yellow-white heartwood color, whereas smoking did not largely change the heartwood color. Almost no differences in the amounts of extracts and metal ions were found in the control and treated woods. Thermal and smoke treatments decreased the pH from the original 8.1 to 6.0 and 7.4, respectively. The results obtained suggest that the changes of pH by both heating and smoking relate to the heartwood color changes in black-colored sugi. In the heated and smoke-heated woods, redness and yellowness were increased by the subsequent UV irradiation at 365 nm, whereas brightness was decreased. Apparently, the heartwood color of black-colored sugi was changed from yellow-white to red by the UV irradiation, the red color being the normal heartwood color of sugi. However, UV irradiation did not cause significant changes in the heartwood color in the control and smoked woods. These results suggest that UV irradiation of the thermally treated wood showing the resulting yellow-white color recovered the redness as found in normal red-colored heartwood, which seems to be caused by chemical changes of pigments under a weak acidic condition in the black-colored heartwood of sugi.