One-pot Mild Hydrothermal Synthesis of the Nanosheets Constructed Cobalt Silicate Hydroxide Hierarchical Porous Hollow Submicron Spheres as Efficient Adsorbents for Organic Dyes Removal

Uniform Co 3 Si 2 O 5 (OH) 4 hierarchical porous hollow submicron spheres(HPSSs, diameter: 100–220 nm; BET: 353.6 m 2 /g) constructed by ultrathin nanosheets are successfully prepared via a facile mild one-pot hydrothermal synthesis(140 °C, 12 h) in the presence of ethylene glycol by using CoCl 2 ·6H 2 O, NH 4 Cl, NH 3 ·H 2 O and Na 2 SiO 3 ·9H 2 O as the raw materials. Meanwhile, a probable in situ etching and growth mechanism of the Co 3 Si 2 O 5 (OH) 4 hierarchical porous submicron spheres(HPSSs) is proposed. When employed as the adsorbents, the Co 3 Si 2 O 5 (OH) 4 HPSSs exhibit satisfactory adsorption performances for probe anionic dye Congo Red(CR) and cationic dye Rhodamine B(RhB), and the maximum adsorption capacities for CR and RhB are confirmed as 576 and 470 mg/g, respectively, higher than those of many other reported typical adsorbents. Both the adsorption isotherms and kinetics for CR and RhB follow the Langmuir and pseudo-second-order models. When the mimic industrial wastewater simultaneously containing CR and RhB is examined, the Co 3 Si 2 O 5 (OH) 4 HPPSs can enable a fast removal efficiency as 99.9% within 3 min. In addition, the adsorption mechanism of the probe dyes on the HPSSs is discussed, and the satisfactory recycling performances also reveal the as-synthesized Co 3 Si 2 O 5 (OH) 4 HPSSs as highly efficient adsorbents for the removal of CR and RhB from mimic wastewater.