Preparation of adsorbent
Different form of tea (black, green and waste) used as carbon
precursors were collected from commercial source and household
uses. These raw materials were then washed with distilled water to
remove the water soluble impurities and surface adhered particles
and then dried in oven at about 60 C to remove moisture and
volatile impurities. The dried materials were then grinded to fine
powder and sieved by mesh size of 60 to make fine powder of
uniform size. The carbon precursor was impregnated with 85%
phosphoric acid (PA) by varying the chemical ratio from 1:1
[precursor:activating agent (w/v)] to 1:3 and kept in oven at 60 C
for 3 h with occasional stirring. The acid impregnated carbon
precursors were placed in a horizontal temperature programmable
furnace for thermal treatment under nitrogen (N2) atmosphere.
The heating rate for all the samples were fixed on 5 C/min. The
temperature ramping was programmed in a continuous and
segment wise (S) heating with a holding temperature of 1 h in each
segment from 200 C to next desired temperature with 100 C
interval. After cooling down to normal temperature, the carbonized
sample was washed initially with 0.1 M HCl and then with
distilled water till a neutral supernatant was obtained. A detail
study was undertaken to optimize the synthetic method [41]
under different condition of acid impregnation ratio, heating
temperature, dwelling time, etc. Allthe PA treated PC samples were
coded as BTPA, WBTPA and WGTPA for black tea and waste black or
green tea, respectively followed by their impregnation ratio and
maximum temperature with holding time in hour in case of
continuous heating otherwise “S” for segment wise heating
afterwards. All the studied samples were dried at 110 C for 24 h
and stored in desiccators for further analysis. Experimental results
obtained for the carbon under optimized condition having
maximum BET surface area are presented in this manuscript.
Adso