A further increase in the dye solution to 8134 µL in total 10 mL volume of the mixture, caused a further decrease in % decolorization, down to 58, 73 and 89 after 2, 10 and 60 min intervals, respectively. Figure shows the absorption spectra of the aliquots collected after 2, 10 and 60 min of CD + ABS process for all the samples containing varying concentrations of the dye solutions. Control experiments were performed using only MnO2 particles and only H2O2 (as oxidant), but negligible decolorization was observed (data not shown), as previously observed also. Figure . Visible light absorption of R6G dye before and after decolorization. (A) 2500 µL (B) 3500 µL (C) 5500 µL and (D) 8134 µL R6G in 10 mL total vol. Figure summarizes the dye removal efficiency of the MnO2 micromotors with respect to remediation time. Figure shows the plot of the degree of decolorization with respect to increasing volumes of dye solution in the mixture. We also studied the effect of the quantity of MnO2 micromotors on the dye decolorization efficiency. Using 1, 2.5 and 5 mg of particles, the decolorization experiments were performed for the reaction mixture containing 2500 µL of R6G. The quantity of particles turned out to be a limiting factor for water decolorization. Using 5 % H2O2 and 0.1 % SDS, 1 and 2.5 mg of MnO2 particles resulted in lesser extent of decolorization, irrespective of the reaction time. The highest decolorization was observed when 5 mg of the particles was used (Figure ). The effect of H2O2 concentration on the dye removal efficiency in the case of less contaminated sample (2500 µL) is depicted in Figure . The concentration of H2O2 was varied as 1, 2.5 and 5%. In 1% fuel, the decolorization efficiency was 82%, but a negligible difference in efficiencies was observed in 2.5 and 5% H2O2 solution. However, % decolorization was decreased as the level of contamination increased, for instance in samples containing 8134 µL of the dye solution. This implies that a faster motion of the particles and great quantity of O2 bubbles produced at higher fuel concentration is required to decolorize concentrated polluted samples. The lifetime of MnO2 particles was sufficiently long enough that after 1h of remediation process, a refuelling of the reaction mixture with fresh H2O2 resulted in re-initiation of bubble formation. However, after several hours, addition of further H2O2 did not produce bubbles, which might be due to the degradation of MnO2 particles. The reaction of MnO2 and H2O2 is very complex and can be either catalytic or non-catalytic, depending upon the solution pH. A neutral or alkaline pH promotes a catalytic reaction, but an acidic pH leads to a non-catalytic reaction that results in the degradation of MnO2 particles. Some general reactions of MnO2 and H2O2 are as follows, which explain the degradation of MnO2 particle.