Environmental Engineering Reference
Determination of Anion Exchange Capacity
the adsorbent in 20 mL conductivity water was titrated against standardAgNO 3
solution.ThetitrationwasrepeatedforstandardNaClwiththesameAgNO 3 solu-
tion and the equivalence point in each case was obtained. From the difference in
volumes of AgNO 3 solutions required, AEC was calculated using the formula,
AEC= NV / W where N is the normality of AgNO 3 solution and V is its volume
required by W g of the adsorbent.
The adsorption experiments were carried out by batch adsorption process, in which
50 mL of aqueous adsorbate solution was mixed with 1 g of the adsorbent in an
Erlenmeyer flask (polypropylene Erlenmeyer flasks were used for F − adsorption).
for a pre-determined time interval and the mixture was centrifuged. Unadsorbed
As(III) in the supernatant was determined using atomic absorption spectrometer
When the effect of pH was studied, the pH of the adsorbate solution was adjusted
by adding aqueous solution of 0.01 N NaOH or 0.01 N HNO 3 in drops. The condi-
tions for different sets of experiments are given in Table 1 .
Results and Discussion
Effects of pH
The pH of the aqueous solution is a significant controlling factor in adsorption
mechanism. The experiments were conducted by varying pH of the solution from
6.0 to 8.5 and taking 1.5 mg/L luoride and 100 ʼg/L arsenite solutions at room
adsorbents ( q e ) increased up to pH = 7 in both the cases (Fig. 1 ), but the increase was
not as sharp for arsenite as it was for fluoride.
had to compete with increasing number of hydroxyl ions in the solution resulting in
less adsorption. Similar results were obtained by using pumice (Malakootian et al.
2011 ).As pH increased toward 7.0, the anionic species, H 2 AsO 3 − , increased and
inhibition was observed at basic pH range and could be attributed to the accumulation