Abstract: A process for fluoride removal from wastewater streams produced during industrial operation for further industrial use or to comply with environmental regulations. The process segregates the removal of fluoride and fluorosilicate ions, from the totality of ions in the waste water stream, thus improving treatment efficiency and reducing costs. Ion-exchange chromatography is used to remove the fluoride and fluorosilicate ions by passing the wastewater stream through one or more columns that contain a charged resin which selectively binds cations/anions in the stream. The fluoride ions are washed from the column and then collected for removal or use in other processes.

Abstract: A process for fluoride removal from wastewater streams produced during industrial operation for further industrial use or to comply with environmental regulations. The process segregates the removal of fluoride and fluorosilicate ions, from the totality of ions in the waste water stream, thus improving treatment efficiency and reducing costs. Ion-exchange chromatography is used to remove the fluoride and fluorosilicate ions by passing the wastewater stream through one or more columns that contain a charged resin which selectively binds cations/anions in the stream. The fluoride ions are washed from the column and then collected for removal or use in other processes.

Abstract: An electroless copper plating bath is improved so as to facilitate its regeneration in an electrodialysis cell. The bath includes elevated amounts of an added salt, preferably as Na salt. The elevated sodium ion level serves as additional counter-cation to hydroxyl ion which is produced at the cathode of the electrodialysis cell. The excess anion from the added salt increases the rate of out-migration of by-products, such as formate ions and sulfate ions, relative to hydroxyl ions through an anion permselective membrane.

Abstract: A method is provided for regenerating the spent permanganate ions in an alkaline permanganate-containing etchant composition by adding to the composition an oxidizer selected from the group consisting of an inorganic bromate, hypochlorite, chlorite, chlorate, peroxydisulfate, monopersulfate and mixtures thereof.

Abstract: Aqueous, alkaline liquid NaMnO.sub.4 solutions are provided which provide excellent resin desmearing and etchback, especially in the manufacture of printed circuit boards. The solutions comprise water, alkali metal hydroxide, NaMnO.sub.4 and from about 0.1 to about 3.0 moles per mole of MnO.sub.4.sup.- of a co-ion for MnO.sub.4.sup.- selected from the group consisting of K.sup.+, Cs.sup.+, Rb.sup.+ and mixtures thereof.

Abstract: Aqueous, alkaline, liquid solutions consisting essentially of NaMnO.sub.4 and NaOH provide high etch rates for, e.g., printed circuit boards. The solutions can be used to desmear and etchback, and produce manganese residues on the surface of the board which are readily removed by acid neutralization alone.