Asymmetric gemini surfactants modified vermiculite- and silica nanosheets-based adsorbents for removing methyl orange and crystal violet

•Adsorption behaviors of CV and MO onto Vt, SiNSs, OVts and OSiNSs were compared.•OVts, OSiNSs were prepared by asymmetric gemini surfactants with varied spacers.•SiNSs exhibited conspicuous adsorption capacity towards CV (qmax = 752.6 mg g−1).•The adsorption of MO onto OVts followed the order: 22-3-6-Vt > 22-2-6-Vt > 22-6-6-Vt.•The spent 22-3-6-Vt and SiNSs could be regenerated at least three times.