The results obtained from extraction using base are shown in Table 5-3. The graph
of actual amount of arsenic on activated alumina with amount of arsenic extracted using
base (sodium hydroxide) is shown in Figure 5-3.
Figure 5-3 indicates that extraction efficiency of sodium hydroxide to extract
arsenic is around 84%. However, the results obtained for both types of extraction were
similar i.e. efficiency of 85-90%.
Flux Meter Bench Scale Experiments
The UF flux meter was tested in the lab for its ability to determine arsenic
contaminant flux. Dimensionless cumulative mass () for activated alumina was
calculated (equation 2.15) from given parameters (section of materials and methods) to
be 0.59. Since this is less than 0.6, the linear relation developed by Klammler (2001) was
used to calculate mass of imaginary tracer retained in the flux meter (equation 2.15) as
1-m t = 1.2 qAt (5.1)
20Rkontr
Since the hydraulic conductivity of activated alumina (4.82 cm/min) is more than
the hydraulic conductivity of Ottawa sand (4.45 cm/min), the specific discharge through
flux meter was different from that through the surrounding aquifer. Therefore, to
calculate specific discharge in flux meter, qo was multiplied with a factor of 1.04
(equation 2.16). Also, from the extraction experiment the amount of arsenic sorbed per
unit mass of activated alumina was obtained. If this sorbed mass is denoted by moont, then
the concentration of arsenic in the solution as indicated by flux meter can be calculated as
(using equation 2.14, 2.15 and 2.17)
C = cntpr (5.2)
0.6qAt