Adsorption performance of polydopamine-modified attapulgite granular adsorbent for methylene blue

Polydopamine-modified granule organo-attapulgite adsorbent (PDA-GOAT) was facilely prepared via a dip-coating approach. The samples were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Surface area and pore size were calculated from the Brunauer–Emmett–Teller method by N₂ adsorption–desorption isotherm. The adsorption behaviour of methylene blue (MB) onto PDA-GOAT was systematically investigated. The experimental data revealed that the adsorption process fitted well with the pseudo-second-order kinetics equation and the adsorption isotherm fitted better with the Langmuir model. Thermodynamic analyses illustrated that MB adsorption onto PDA-GOAT was a physisorption endothermic process. Importantly, PDA-GOAT can be regenerated by NaBH₄ aqueous solution. The obtained results prove that PDA-GOAT can be a superior reusable adsorbent for the removal of MB from effluent.