Results and discussion
3.1. Determination to the adsorption experimental conditions
3.1.1. The determination of adsorption time for activated carbon
in coking wastewater treatment
The influence of adsorption time of activated carbon on the COD
of the wastewater was determined by placing 1 g of activated carbon
into tapered bottles containing 100 ml of coking wastewater
at 25 ◦C and then shaking the bottles in an electrothermal constant
temperature incubator for different time periods (Fig. 1).
It can be seen in Fig. 1 that as the adsorption time increased, the
COD removal efficiency of activated carbon in coking wastewater
increased. When the adsorption time reached 20 min, however, the
COD removal efficiency decreased slowly. These can be explained
that for activated carbon, the saturated adsorption of chemicals
in the wastewater needed to be completed gradually in a certain
time, and the equilibrium establishing between adsorption
and desorption of chemicals on activated carbon surface needed
a longer period of time. This result shows that the adsorption of the
chemicals in the wastewater on the activated carbon could reach
saturation in 20 min. Based on these results, it was determined that
the best adsorption time for activated carbon in wastewater was
20 min.