Mechanochemical modification of biochar-attapulgite nanocomposites for cadmium removal: Performance and mechanisms

Biochar prepared from natural loofah sponge has been used as adsorbent for the removal of contaminates or soil amendment, but the performance is still less than satisfactory. Herein, loofah sponge biochar-attapulgite nanocomposites were prepared through mechanochemical process. The Si-O-C and more oxygen-containing functional groups were found on the surface of nanocomposites by FT-IR, which provides great contributions to the effective removal of Cd(II). Moreover, Si2p peak at 102.9 eV occurred in XPS of biochar-attapulgite composites. Batch adsorption experiments were investigated to compare cadmium adsorption performance of origin biochar (B450), ball-milled biochar (BM450) and nanocomposites (B x P y M). The measured maximum adsorption capacity of B 1 P 1 M (mass ratio = 1:1) for Cd(II) with the initial concentration 200 mg L −1 is 102.26 mg g −1 , which is approximate two times than that of pristine biochar. Moreover, the rapid removal of Cd(II) (C 0 = 25 mg L −1 ) on B 1 P 1 M reached 76.0% in the initial 5 min. The modified model of Freundlich isotherm and pseudo-second-order fit the Cd(II) adsorption data well. The mechanism for Cd(II) removal may be attributed to the synergistic effects of silicate precipitate, acid-oxygenated groups complexation, and electrostatic-type interaction. Therefore, biochar-attapulgite composite (B 1 P 1 M) could be used as an environmentally friendly adsorbent on account of low cost and fast adsorption rate for waste water treatment on an industrial level. • Dried loofah sponge was used to prepare biochar. • Biochar-attapulgite nanocomposites were obtained by mechanochemical process. • Nanocomposite B 1 P 1 M exhibited fast removal rate reached 76.0% in the initial 5 min. • SiO 2 complexation and electrostatic interaction constitute the main sorption force.