The effect of pH modifier on the flotation of celestite with sodium oleate and sodium metasilicate
Abstract This paper studies the influence of two pH modifiers, namely sodium hydroxide (NaOH) and sodium carbonate (Na 2 CO 3 ), on the flotation of celestite ore using sodium oleate as the collector and sodium silicate (Na 2 SiO 3 ) as the depressant. The use of Na 2 CO 3 provides the best results for the concentration of celestite, under the same experimental conditions.
Separation of sillimanite from beach sands contaminated with shell
Sillimanite is a very important raw material for the manufacture of refractory bricks used in iron and steel, 
cement and glass industries. In some coastal stretches of 
south India, the beach sand is contaminated with shell. After recovering heavy minerals like ilmenite, rutile, zircon and garnet by various physical separation techniques, the final sand containing sillimanite, quartz and shell is presently dumped as waste. Separation of sillimanite from these rejects was studied by flotation process using oleic acid and octylhydroxamate as collectors for selective flotation of sillimanite. Starch and tannin were tried as depressants for shell and sodium silicate as dispersant for quartz. Though the quartz could be depressed effectively, the shell was found to float along with sillimanite both in the presence of oleic acid and octylhydroxamate. When starch or tannin was added to suppress the shell flotation, the floatability of 
sillimanite and in turn its recovery was drastically affected. Alternatively shell was totally removed by treating with dilute hydrochloric acid and sillimanite was separated from quartz using oleic acid and sodium silicate. The concentrate analyzing 97% sillimanite free from shell were achieved from the initial sand assaying 48 % sillimanite, 46 % quartz and 3.3% shell.
The Effects of Certain Polymers on Tensile strength and Tension Relaxation of Wet Web
The trend in papermaking has been towards lower basis weights, decreased amounts of softwood kraft pulp and an increased use of fillers and recycled fibers. All these changes tend to result in lower strengths of both wet and dry web. To maintain necessary strength in the papers, a greater quantity of strength additives is often required. The effect of different polymers on the dry paper strength has been widely studied and the action of mechanism of different polymers is quite well known. There is much less information of their effect on wet web properties, and especially on the tensile strength and relaxation characteristics. In this laboratory scale study, the effects of adding different polymers by spraying on wet web tensile and relaxation characteristics at high strain rate were examined. The sprayings were done on wet paper sheets before wet pressing. The results showed that spraying of polymers significantly improves wet and dry paper tensile strength without any increase in dry paper density. The effect of different polymers on wet web mechanical properties was characteristic for each polymer. Carboxymethyl cellulose (CMC) and chitosan improved wet web tensile strength at dryness levels higher than 55%, while polyvinyl alcohol (PVA) improved wet web tensile strength also at lower dryness levels. The most prominent increase in dry and wet web tensile strength was obtained by sequential application of oppositely charged polymers. However, the relative increase of tensile strength was significantly higher for the wet web (80% increase) than for the dry paper (35% increase) compared to the reference without added polymer. Also the mode of polymer addition had a significant effect on wet web tensile strength. Despite a significant increase in the wet web strength, only minor effects on the residual tension (tension after 0.475 s relaxation) was observed. Based on this result, it was concluded that spray addition of the polymers used in this study increased molecular level interactions between fibers but had no effect on the fiber network activation.