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 H 2 O 2 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 H 2 O 2 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.% H 2 O 2 . 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 MnO x motors contained in the pelagic clays.