The issue of using electroplating sludge to produce sulfur dioxide for the manufacture of sodium sulfite

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Problems associated with using electroplating sludge to produce sulfur dioxide for the manufacture of sodium hydride: 1. The solution used for purifying sulfur dioxide through water treatment is black, with a pH of 3–4. 2. The solution in which sodium carbonate is used to absorb sulfur dioxide is yellow, with a pH of 6–7. Analysis of the solution’s composition using ICP revealed the following concentrations in g/t: zinc 8653, calcium 3754, iron 1842, boron 1691.7, potassium 4575.1, magnesium 919.1, silicon 597.2, manganese 241.2. Small amounts of other ions such as chromium, platinum, rhodium, palladium, rubidium, lithium, lead, mercury, germanium, and nickel were also present. Neither acids nor bases can remove the color from this solution; adding a base turns the solution dark green. What are these inorganic ions? Or did it go into organic substances, like bromine? Furthermore, the grade of the obtained sodium suboxide is only a little over 30%, with 60% being sodium sulfate. Please ask the experts to analyze and provide answers