Apparatus and instruments
All the apparatus used were soaked in concentrated HNO3
for 12 h and then washed initially with tap water and then
with distilled water. Then the apparatus were dried in hot air
oven. Modified Gutzeit apparatus containing scrubber with lead
acetate-soaked glass wool, and delivery L tube, were used for
the production of AsH3 gas. A digital pH meter (Orion, London)
was used for all pH measurements. A high precision
electrical balance (Sartorious GmbH) was used for weighing.
All absorbance measurements were carried out with a spectrophotometer
(Thermo Spectronic UV1, UK) equipped with
1-cm quartz cells. A mechanical shaker was used for shaking
purpose. Gilson micropipette with disposable tips was used
to add sample. Fe(III) and Al(III) concentrations were measured
using atomic absorption spectrophotometer (Shimadzu
AA-6650). Sorptomatic 1990 was used for BET analysis. JEOL
JSM-5800 scanning electron microscope was used for SEM
and EDX studies. Powder X-ray diffraction (XRD) pattern was
recorded using a Philips PW-1710 model X-ray diffractometer
and Cu K radiation. The XRD data was analyzed by the X’Pert
HighScore Philips analytical software.