Method of and apparatus for treating liquors by magnetic filtration

Treatment of liquors by magnetic filtration is made effectively by accurately controlling the ferrous/ferric ratio of iron ions in the liquor by adding a reducing agent. This has the effect that when the iron is precipitated, it is precipitated in the form of magnetite which is susceptible to high efficiency magnetic filtration. In the absence of control of the ratio, between 0.4 and 0.6, ferrous or ferric hydroxide might be precipitated and this is difficult to handle. Other contaminants are coprecipitated with or adsorbed by the iron floc. Measurement of the solution potential, between 0.35 and 0.4 volts, is used to determine the ferrous/ferric ratio. The apparatus includes a treatment vessel with a solution potential probe, supply lines for reducing agent and for precipitating agent, and a magnetic filter. (author)