The application of activated carbon produced from waste printed circuit boards (PCBs) by H3PO4 and steam activation for the removal of malachite green

• Waste printed circuit boards (PCBs) are used as precursor of activated carbon.
• A novel activation method which combines H3PO4 and steam was studied.
• The properties of AC-H3PO4, AC-H3PO4-Steam and AC-H3PO4/Steam were discussed.
• AC-H3PO4/Steam had more functional groups than AC-H3PO4-Steam.
• Adsorption kinetics and adsorption isotherms were investigated.

Waste printed circuit boards (PCBs) are used as precursor for activated carbons preparation by three ways, that is, AC-H3PO4 is prepared by phosphoric acid activation; AC-H3PO4-Steam is prepared by the steam reactivation to AC-H3PO4, and AC-H3PO4/Steam is prepared by impregnation with phosphoric acid followed by steam. The activated carbons obtained under optimum conditions were characterized using N2 adsorption/desorption isotherms, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Batch adsorption studies were performed to evaluate the adsorption properties of the three adsorbents toward malachite green (MG). Compared with AC-H3PO4, AC-H3PO4-Steam has higher BET surface area (SBET) and microspores content, and less functional groups, indicating steam reactivation has an obvious advantage in improving the physical structure, chemical properties and adsorption capacities of activated carbons. While AC-H3PO4/Steam showed higher yield, lower SBET, more functional groups and higher adsorption capacities for malachite green than that of AC-H3PO4-Steam. For the three adsorbents, the adsorption kinetics followed the pseudo-second-order model. Adsorption experiments indicated that adsorption data fitted the Langmuir equation best than Freundlich and Dubinin–Radushkevich (D–R) models for AC-H3PO4, AC-H3PO4-Steam and AC–H3PO4/Steam. The adsorption has been confirmed to be an endothermic and spontaneous process through the thermodynamic parameters.