Synthesis of 13X zeolite from alkaline waste streams in the aluminum anodizing industry

Several alkaline baths are used to prepare aluminum pieces before they are anodized, and after certain operation times, they have to be renewed. Usually, spent baths are neutralized with acid effluents, doubling the cost, the treatment, and the loss of the aluminum and caustic soda content. In this paper, the synthesis of 13X zeolite is proposed as a recovery process. The aluminum content is recovered in this zeolite, which has applications in the formulation of detergents, and a solution of caustic soda and silicate is obtained as a byproduct that could be reused in new synthesis processes or other alkaline operations. The reaction temperature and time were selected through an initial series of experiments, and the molar ratios that define the batch composition were optimized through experimental design.