The original granules (ceramic adsorbent before sintered) were
grayish yellow, while the ceramic adsorbents became brick-red
after treatment. The change was result from the high-temperature
calcination. The surface charges of the original granule (zeta potential
30.1 mV) and the ceramic particle (zeta potential 31.2 mV)
were not obviously changed. The surface areas of the original granule
and ceramic particle are shown in Table 1. When the original
granules were sintered to ceramic particles, the BET surface area
increased from 33.59 to 36.80 m2 g1, and the total pore volume
enlarged from 0.08 to 0.10 mL g1. It indicated that more pores
were created successfully during the burning of the soluble starch
as porogen. The BJH (Barrett–Joyner–Halenda) adsorption pore size
distribution is shown in Fig. 1a. The BJH adsorption pore size distributions
revealed that the observed pore sizes mostly varied between
2 and 50 nm (65.72%). According to the IUPAC
classification, the ceramic adsorbent is classified as a mesoporous
material. The pore sizes under 6 nm and over 80 nm were 13.77%
and 16.35%, respectively. The surface morphology of the ceramic
adsorbent was examined by SEM (Fig. 1b and c). Fig. 1b shows
the pristine surface features of the ceramic adsorbent, while
Fig. 1c presents the changed surface features after ammonium
adsorption at a magnification of 1000. In Fig. 1b, irregularly sized
surfaces are covered with fragmentary texture, while the fragments
disappear, and they are intertwined with filamentous and
acicular surfaces after ammonium adsorption in Fig. 1c. This
change suggests that inevitably the ammonium adsorption occurred
on the surface of the particles, and the adsorption occurring
in the inside surface area of the pores presumably also existed. The
XRD pattern of the ceramic adsorbent is shown in Fig. 1d. It revealed
that the mainly chemical compositions of the developed
ceramic adsorbent were salic minerals, and Na2SO4 was successfully
impregnated in the ceramic adsorbent. Na+ has beenproved
the most common and effective exchangeable cation for NHþ4
.
The available Na+ of the ceramic adsorbent predicts that the ceramic
adsorbent might have good adsorption ability for ammonium
ions.