Rice straw as precursor of activated carbons: Activation with ortho-phosphoric acid

Highly mesoporous activated carbons (ACs) with a mesopore fraction ranging from 42 to 73% were obtained by activation of rice straw (RS) with ortho-phosphoric acid (PA). Due to such a high mesoporosity, these ACs can be successfully used for pollutant removal in aqueous phase. The ACs were prepared at activation temperatures (T) ranging from 350 to 500 °C, using PA to RS weight ratios (R) from 0 to 1.6 and activation times from 0 to 2 h. They were characterised by nitrogen adsorption at −196 °C, SEM-EDX, and methylene blue adsorption. RS is a very heterogeneous material with a variable content of mineral matter: using the product of activated carbon yield multiplied by surface area (C × SBET) as the performance criterion, the best AC was produced at T = 450 °C and R ≥ 1. These conditions lead to SBET higher than 500 m2 g−1 and a C × SBET around 270 m2 g−1.