Physico-chemical aspects of zeolite-A synthesis and application for environmental safe detergents

Abstract

Synthesis of zeolites is characterized by a long lag crystallization period. However, this period is not dead; many precrystallization processes are active, leading to nucleation, followed by rapid crystallization. The most lag-active species are complexes of aluminum and, to a lesser extent, silicium and sodium. If these complexes are exposed to non-equilibrium conditions or outside stress, modified zeolite-A can be obtained. This zeolite has a few properties important for surfactants: significantly higher rate of Ca2+ exchange, lattice windows large enough for Mg2+ binding (21 mg Mg2+ per g zeolite) and increased sorption capacity for nonionics and co-polymers. — In connection with trends (compact detergents) the outside zeolite surface area plays an important role. Only under non-equilibrium conditions can zeolite synthesis lead from low (1.3–2.6 m2/g) to high surface area (9–12 m2/g). Modification can also be made, respective catalytic or inhibitory properties for bleaching substances like perborate or peracids. — Appearance of huge quantities of zeolite in the environment (precostal and sludge fertilized field) might have negative side-effects. However, results with six microorganisms (Staphylococcus aureus — gram positive, Escherichia coli — gram negative, Bacillus subtilis, Thrichophyton mentagrophytes, Candida albians and Aspergillus fumigatus) show significant bactericidal effects. The effect is highest for the dangerous Thrichophyton mentagrophytes fungi; already 0.1% of zeolite suspension at 20°C is sufficient. In this respect, and due to high affinity for heavy metals, zeolite suspension at 20°C is sufficient. In this respect, and due to the high affinity for heavy metals, zeolite behaves as an environmental cleaner. Results with different algal species are not conclusive within the limited laboratory period of examination that has been conducted.Key wordszeolite-A — synthesis — impure raw material — particle size — ion exchange capacity