Zwitterionic form of RhB dominates at pH greater than that
of RhB pka hence attraction between the xanthene
and the carboxyl groups
of RhB monomers occurs resulting into RhB dimers
and subsequently a decrease
in RhB adsorption [33].
Optimum adsorption at pH of 3 has been previously reported by researchers [34].
Subsequent adsorption studies were carried out at the optimum pH.