Z. jujuba, also named as
Nebka (NB), can be carbonized with chemicals such as ZnCl2, KOH and
H3PO4 in a furnace at high temperatures in the absence of oxygen to
produce carbon chars. Their treatment with oxidizing agents in liquid
or gaseous phase, such as air, oxygen, KMnO4, H2O2 and particularly nitric
acid (HNO3), is a commonly used method that introduces oxygenated
groups and increases the polarity of the surface of the adsorbent and,
consequently, their selectivity for ionic compounds.