Aluminum recovery from water clarifier sludges by ion exchange: Comparison of strong and weak electrolyte cation resins performances

Technical feasibility of an ion exchange based process for removal and recovery of the coagulating principle (Al, Fe chemicals) from water clarifier sludges is illustrated. The innovation is a typical example of 'conservative technology' applied to the solution of environmental problems, thus allowing for the minimization of the environmental impact related to the disposal of the solid wastes, through conditioning and detoxification of the sludges for land application, and simultaneous recovery of valuable products from non-conventional sources. The paper illustrates laboratory scale comparative experiments between weak (carboxylate) and strong (sulphonic) cation resins performances in reference to a typical acidic leachate from water clarifier sludges (pH 3.5). Together with mechanistic interpretation of the multicomponent-polyvalent Al/Fe/Na ionic system involved, in this paper indications for process optimization are also given