Synthesis of zeolite Na-P1 under mild conditions using Brazilian coal fly ash and its application in wastewater treatment

Abstract

Zeolites may be easily obtained from coal fly ash by conversion processes based on the similar essential composition of both. Among the existing zeolites, we highlight the Na-P1 which is normally produced by hydrothermal treatment, this zeolite has been synthesized in pressurized reactors at high temperatures. The purpose of this study was to synthesize Na-P1 zeolites under mild conditions using Brazilian coal fly ash. Zeolite Na-P1 was produced simultaneously in pressurized reactors at 150°C and a glass reactor at 100°C. Complementary synthesis parameters were also evaluated, such as concentrations of alkali, crystallization time, previous separation of magnetic material from the ashes and effects of seeding on synthesis. The zeolite synthesized in the optimized process (77% Na-P1) was used to remove contaminants from acid mine drainage (AMD). Treatment of this wastewater with 10gL−1 of synthetic zeolite for 30min presented high removal of arsenic, nickel, calcium, copper, iron and manganese ions and the partial yet significant removal of ammonium, magnesium, potassium and zinc ions. This performance indicates that the synthetic zeolite has excellent adsorption characteristics and can be an alternative for the treatment of DAM. As such, synthesis under mild conditions in a glass reactor is practical, reducing energy costs and minimizing environmental impacts, with the possibility of reproducing zeolite synthesis on an industrial scale.