Abstract: Phosphorus mud and other phosphorus-containing waste materials are processed to remove water and phosphorus and to leave a solid mass which is safe for disposal. The phosphorus mud is heated to boil off the water and then to boil off yellow phosphorus, which is subsequently condensed. The residual phosphorus then is removed mainly by burning off in air along with some volatilization, so as to increase the recovery rate of solids from the waste material, when compared to removal of residual phosphorus by volatilization under nitrogen. A significant improvement in processing rate is achieved at the expense of a loss of a minor amount of recoverable phosphorus.

Abstract: Phosphorus furnace slag is used as a ladle flux and/or as a tundish flux in the continuous casting of steel. The phosphorus furnace slag uniquely combines the properties of thermal insulation, oxidation protection and inclusion absorption necessary to function satisfactorily as a ladle flux and/or as a tundish flux.

Abstract: Chlorine is selectively cathodically electrolytically removed from aqueous solutions of chlorine dioxide and chlorine by the application of an electrode potential at a pH of the aqueous solution of up to about 4. Chlorine is electrolytically reduced to chloride ions while the concentration of the chlorine dioxide remains substantially the same in the treated solution. The chlorine reduction is effected directly at pH values up to about 2 using a low overpotential cathode and indirectly at pH values up to about 4 using a high overpotential cathode.

Abstract: The extent of delignification of chemical pulps by oxygen-containing chemicals, preferably hydrogen peroxide, is enhanced by demethylating the pulp prior to such oxidative delignification, to a degree of demethylation of at least about 30%, preferably at least about 50%. Demethylation may be achieved by chemical treatment of the already-formed pulp or by modification to the pulping process to result in demethylated pulp.

Abstract: Soluble hexavalent chromium values are removed from aqueous chlorate solutions by employing a critical effective ratio of OH.sup.- :Cr.sub.2 O.sub.7.sup.= ions of at least 3:1 in the aqueous chlorate solution and by employing a dithionite to reduce the hexavalent chromium to trivalent chromium, preferably in the mole ratio of S.sub.2 O.sub.4.sup.= :Cr.sub.2 O.sub.7.sup.= of at least 3:1. The trivalent chromium forms chromic hydroxide (Cr(OH).sub.3) with the hydroxyl ions and precipitates from the aqueous chlorate solution. The process is rapid and effective in quantitative removal of hexavalent chromium from the aqueous chlorate solutions and is especially useful for the removal of sodium dichromate from cell liquor which is intended to be employed in chlorine dioxide production and which is produced by diaphragmless electrolysis of sodium chloride.

Abstract: Dichromate values, or other soluble hexavalent chromium values, are removed from cell liquor or other aqueous media containing the same by cathodically reducing the same to trivalent chromium, which deposits on the cathode as chromium hydroxide. The cathode has a high surface area three-dimensional structure which exposes the electrolyte to electrolysis for a relatively long period of time. An electrode potential of about 0 volts vs. SCE is applied to the cathode.

Abstract: Dissolved arsenic (III) contaminant is removed from mineral acids, such as hydrochloric acid, by electrolysis using a high surface area cathode having a three-dimensional electrolyte-contacting surface which exposes the electrolyte to electrolysis for a relatively long period of time. The dissolved arsenic is reduced to arsenic metal, which then plates out on the cathode. Dissolved concentrations of arsenic of less than 1 ppm can be achieved using the invention.

Abstract: Chlorine dioxide is transferred by membrane pervaporation from one chamber filled with aqueous chlorine dioxide-generating reactants or other chlorine dioxide donor medium across a gas-permeable hydrophobic membrane to a recipient aqueous medium filling a second chamber. The recipient medium may be water, pulp suspension or sodium chlorite solution. The membrane typically is expanded polytetrafluoroethylene.

Abstract: Chlorine dioxide is generated at high efficiency from feeds of chlorate cell liquor, sulphuric acid and methanol by a hybrid of reaction of sodium chlorate with sulphuric acid and methanol and reaction of sodium chlorate with sulphuric acid and sodium chloride. The reaction medium is maintained at its boiling point under a subatmospheric pressure while sodium sesquisulphate precipitates from the reaction medium.