RhBwas analyzed using a UV–vis spectrophotometer (UV2400). pH was measured by a pH meter (PHS-25).
3. Results and discussion
3.1. The texture properties of activated carbons
The texture properties of different activated carbons are summarized in Table 1. P-AC presented low BET surface area(892 m2g−1) and small pore volume (1.48 cm3g−1). A significantin crease in BET surface area and pore volume was observed whenthe P-AC was treated by hot water or KOH. PK-AC exhibited higher BET surface area and pore volume than P95-AC. K-AC showed thehighest surface area and pore volume. P-AC, P95-AC and PK-AC mainly contained mesopore (Fig. 1 and Table 1). In the case of K-AC, the micropore surface area could achieve 1323 m2g−1, which exceeded its mesopore surface area (1193 m2g−1). In a word, theBET surface areas of the four materials increased according to thesequence: P-AC < P95-AC < PK-AC < K-AC.
3.2. Effect of different activated carbon on adsorption
The amount of RhB adsorbed onto the four activated carbons was in the following order: K-AC > PK-AC > P95-AC > P-AC (Fig. 2).This was consistent with the changing trend of BET surface area.Taking into account the cost of activated carbon, here, our work mainly focus on the investigation of PK-AC. It was noteworthy that most of pores in PK-AC were lager than 2 nm (Fig. 1b), which were 0.0