Abstract: The invention is directed to an improvement in operation of wash columns, and more in particular to an apparatus for separating solid particles from a slurry and to a process for separating solid particles from a mother liquor slurry. The apparatus of the invention comprises a wash column (1), which comprises a melting circuit (8,10,11,21), wherein means (22,23) are present to introduce a compound or composition to said wash column between a wash front (6b) formed in said wash column in operation and a product outlet and/or in the melting circuit.

Abstract: Disclosed is a method of purifying a solution containing hydrofluoric acid, nitric acid and at least one silicon impurity by treating the solution with at least one reverse osmosis membrane. According to the method of the present invention, silicon impurities contained in the solution containing hydrofluoric acid and nitric acid can be selectively removed or reduced. This method can be advantageously used in the photovoltaic industry or in the battery component industry.

Abstract: Disclosed is a method of purifying a solution containing hydrofluoric acid, nitric acid and at least one silicon impurity by treating the solution with at least one reverse osmosis membrane. According to the method of the present invention, silicon impurities contained in the solution containing hydrofluoric acid and nitric acid can be selectively removed or reduced. This method can be advantageously used in the photovoltaic industry or in the battery component industry.

Abstract: The invention is directed to an improvement in operation of wash columns, and more in particular to an apparatus for separating solid particles from a slurry and to a process for separating solid particles from a mother liquor slurry. The apparatus of the invention comprises a wash column (1), which comprises a melting circuit (8,10,11,21), wherein means (22,23) are present to introduce a compound or composition to said wash column between a wash front (6b) formed in said wash column in operation and a product outlet and/or in the melting circuit.

Abstract: Process for purifying a stream comprising phosphoric acid and a first amount of impurities, comprising: forming a slurry of phosphoric acid crystals in a water mother liquor; separating the phosphoric acid crystals from the mother liquor by filtration in a wash column comprising a filtering element, while a packed bed of crystals coming from the slurry forms near such filtering element; washing the separated phosphoric acid crystals in the wash column by bringing a washing liquid in countercurrent to the crystals in the bed up to a wash front, where the washing liquid recrystallizes, the bed being subjected to a movement in the direction of such wash front; forming a purified stream comprising phosphoric acid and a reduced amount of impurities by melting at least part of the washed crystals; and extracting the purified stream from the wash column through a product outlet of the wash column; wherein water is introduced into the wash column, between the wash front and the product outlet and/or in a melting circ