Abstract: In the process for separating off by flotation (pressure release) suspended matter from liquids which are present in a gas-introduction reactor, the suspension to be withdrawn for flotation is conducted at a flow velocity .ltoreq.0.3 m/s against the natural direction of bubble rise, gas being additionally introduced into the suspension. The gas-treated suspension is withdrawn at the bottom of the gas-introduction apparatus and it is fed to flotation.

Abstract: To remove lead and cadmium from phosphoric acid, alkali solution and aqueous sulfide solution are simultaneously introduced with thorough mixing into a phosphoric acid having a P.sub.2 O.sub.5 content of up to 32% by weight, an iron content of up to 0.3% by weight and an alkali/P ratio of up to 0.30. The temperature of the phosphoric acid which is thoroughly mixed with alkali solution and sulfide solution is adjusted to temperatures of 58.degree. to 72.degree. C. with escape of the excess hydrogen sulfide. To complete the sulfide precipitation, the temperature is lowered to below 45.degree. C. Finally, the precipitated sulfides of the lead and cadmium are separated off from the phosphoric acid.

Abstract: A process for the removal of solid particles from a mixture containing at least one liquid chlorinated hydrocarbon is described. The solids-containing liquid mixture is introduced into at least one hydrocyclone having a downstream separator. The liquid mixture which has been enriched in solids and discharged from the hydrocyclone is preferably subjected to sedimentation of the solid particles, without the use of centrifugal forces. Efficient removal of interfering particles is achieved in this way, together, with long service lives and a minimum of emission.

Abstract: Zeolites are prepared by hydrothermal crystallization of alkaline aqueous synthesis mixtures. Normally the zeolites are filtered and washed with water until the filtrate shows a pH of about 9 to 12. Sometimes, especially if the resulting zeolite consists of very fine particles, the zeolite filter cake shows thixotropic properties.If the filter cake is washed with diluted sodium hydroxide or only small amounts of water this thixotropy can be avoided.