An aqueous polysulfide composition comprises one or more inorganic polysulfides, wherein the amount of polysulfides in the composition is at least 30% by weight, preferably at least 35% by weight, more preferably at least 40% by weight, and wherein the amount of thiosulfate anions in the composition is at most 5% by weight, relative to the total weight of the composition. In one embodiment the weight ratio of polysulfides to thiosulfates in the aqueous composition is from 55/1 to 1.5/1. In another embodiment, the aqueous polysulfide composition has a pH of at least 10. A process for preparing an aqueous polysulfide composition comprises reacting a sulfide salt (c) with elemental sulfur to form one or more polysulfide salts. The compositions have many uses and are in particular useful in metal capturing, cyanide scavenging, soil remediation, water treatment, petroleum processing, leather processing, and making of paper pulp.

An aqueous polysulfide composition comprises one or more inorganic polysulfides, wherein the amount of polysulfides in the composition is at least 30% by weight, preferably at least 35% by weight, more preferably at least 40% by weight, and wherein the amount of thiosulfate anions in the composition is at most 5% by weight, relative to the total weight of the composition. In one embodiment the weight ratio of polysulfides to thiosulfates in the aqueous composition is from 55/1 to 1.5/1. In another embodiment, the aqueous polysulfide composition has a pH of at least 10. A process for preparing an aqueous polysulfide composition comprises reacting a sulfide salt (c) with elemental sulfur to form one or more polysulfide salts. The compositions have many uses and are in particular useful in metal capturing, cyanide scavenging, soil remediation, water treatment, petroleum processing, leather processing, and making of paper pulp.

A method of regenerating an activated carbon catalyst which is used in the production of polysulphide liquor. In the method, the catalyst is washed with a washing liquid in order to remove the sediment accumulated in the catalyst. According to the present invention, in this case, the activated carbon catalyst is regenerated most suitably by bringing it to a multi-stage washing which comprises at least one washing step in which the washing liquid used comprises sodium sulphide, and one washing step in which acidic washing liquid is used. The sulphur precipitate is peeled off using sodium sulphide, and the iron and other metals can be effectively removed by using an acidic washing, without damaging the catalyst.

A method of regenerating an activated carbon catalyst which is used in the production of polysulphide liquor. In the method, the catalyst is washed with a washing liquid in order to remove the sediment accumulated in the catalyst. According to the present invention, in this case, the activated carbon catalyst is regenerated most suitably by bringing it to a multi-stage washing which comprises at least one washing step in which the washing liquid used comprises sodium sulphide, and one washing step in which acidic washing liquid is used. The sulphur precipitate is peeled off using sodium sulphide, and the iron and other metals can be effectively removed by using an acidic washing, without damaging the catalyst.

A method includes contacting a metallic compound comprising a first metallic cation, with a melt comprising a metallic polysulfide comprising a second metallic cation, thereby forming a molten metallic polysulfide of the first metallic cation. The method also includes cooling the melt to form a sulfur phase and a solid phase comprising the molten metallic polysulfide of the first metallic cation.

A method includes contacting a metallic compound comprising a first metallic cation, with a melt comprising a metallic polysulfide comprising a second metallic cation, thereby forming a molten metallic polysulfide of the first metallic cation. The method also includes cooling the melt to form a sulfur phase and a solid phase comprising the molten metallic polysulfide of the first metallic cation.

A method includes contacting a metallic compound comprising a first metallic cation, with a melt comprising a metallic polysulfide comprising a second metallic cation, thereby forming a molten metallic polysulfide of the first metallic cation. The method also includes cooling the melt to form a sulfur phase and a solid phase comprising the molten metallic polysulfide of the first metallic cation.

A method includes contacting a metallic compound comprising a first metallic cation, with a melt comprising a metallic polysulfide comprising a second metallic cation, thereby forming a molten metallic polysulfide of the first metallic cation. The method also includes cooling the melt to form a sulfur phase and a solid phase comprising the molten metallic polysulfide of the first metallic cation.

Alkali metals and sulfur may be recovered from alkali monosulfide and polysulfides in an electrolytic process that utilizes an electrolytic cell having an alkali ion conductive membrane. An anolyte includes an alkali monosulfide, an alkali polysulfide, or a mixture thereof and a solvent that dissolves elemental sulfur. A catholyte includes molten alkali metal. Applying an electric current oxidizes sulfide and polysulfide in the anolyte compartment, causes alkali metal ions to pass through the alkali ion conductive membrane to the catholyte compartment, and reduces the alkali metal ions in the catholyte compartment. Liquid sulfur separates from the anolyte and may be recovered. The electrolytic cell is operated at a temperature where the formed alkali metal and sulfur are molten.

Alkali metals and sulfur may be recovered from alkali monosulfide and polysulfides in an electrolytic process that utilizes an electrolytic cell having an alkali ion conductive membrane. An anolyte includes an alkali monosulfide, an alkali polysulfide, or a mixture thereof and a solvent that dissolves elemental sulfur. A catholyte includes molten alkali metal. Applying an electric current oxidizes sulfide and polysulfide in the anolyte compartment, causes alkali metal ions to pass through the alkali ion conductive membrane to the catholyte compartment, and reduces the alkali metal ions in the catholyte compartment. Liquid sulfur separates from the anolyte and may be recovered. The electrolytic cell is operated at a temperature where the formed alkali metal and sulfur are molten.