Natural zeolites are abundant and low cost resources, which are crystalline hydrated aluminosilicates
with a framework structure containing pores occupied by water, alkali and alkaline earth cations. Due to
their high cation-exchange ability as well as to the molecular sieve properties, natural zeolites have been
widely used as adsorbents in separation and purification processes in the past decades. In this paper,
we review the recent development of natural zeolites as adsorbents in water and wastewater treatment.
The properties and modification of natural zeolite are discussed. Various natural zeolites around
the world have shown varying ion-exchange capacity for cations such as ammonium and heavy metal
ions. Some zeolites also show adsorption of anions and organics from aqueous solution. Modification of
natural zeolites can be done in several methods such as acid treatment, ion exchange, and surfactant
functionalisation, making the modified zeolites achieving higher adsorption capacity for organics and
anions.