Deep‐sea clays using as active Fenton catalysts for self‐propelled motors

Raw deep‐sea clays (i.e., pelagic clays) collected from the Indian Ocean were able to function as Fenton catalysts and self‐propelled micromotors due to the high content of Fe‐ and Mn‐. The pelagic clays were for the first time observed to be automatic in the H2O2 solution. The pelagic clays existed in the form of poorly crystallized marine sedimentation. The major minerals were found as illite/montmorillonite (I/M) and amorphous ferromanganese nodules, and the minor minerals included kaolinite, quartz, feldspar, and calcite. Significant amounts of oxygen bubbles were generated when the clay particles were dispersed into the H2O2 solution (0.1–10.0 wt.%), and the average velocity of the motors was observed as high as 183.0 μm s–1 in 10.0 wt.% H2O2. The self‐propulsion would induce vigorous mixing in local areas of the solution and was confirmed to benefit the catalytic performance. The clays were employed to remove Rhodamine B (RhB) for a proof‐of‐concept study. In the acid solution (pH = 1.0–5.0), the removal of RhB was controlled by the Fenton process accompanied by the adsorption of clay particles. In the alkaline solution (pH = 9.0), the removal of RhB was found to follow an adsorptive bubble separation pathway. Both processes were greatly influenced by the self‐motion of MnOx motors contained in the pelagic clays.