In summary, micro-sized flower-like MgO particles with excellent
performance in photocatalytic degradation of various organic dyes (e.g.,
methylene blue, Congo red, thymol blue, bromothymol blue, eriochrome black T,
and their mixture) had been successfully prepared by a facile precipitation via
the reaction between Mg2+ and CO32−under a temperature of 70 °C. Time-dependent
experiments demonstrated that their formation involved a complex process, in
which after the initial mixture of reactants, the product was prone to turn into
agglomerates or rod-like particles with a formula of xMgCO3·yH2O (x = 0.75–0.77
and y = 1.87–1.96). Because of the chemical instability, they would transfer
into flower-like particles with a composition of xMgCO3·yMg(OH)2·zH2O (x =
0.84–0.86, y = 0.13–0.23, and z = 0.77–1.15).
With extension of the reaction time, the content of Mg(OH)2 in the product demonstrated an increasing trend, whereas an opposite tendency was observed for the level of H2O. In addition, we found that the performance of the flower-like particles in photocatalytic degradation of organic dyes was superior to other morphologies of MgO (e.g., nest-like, spherical, rod-like and trapezoidal structures) due to the stronger adsorption ability to organic dyes. The developed catalyst also demonstrated an excellent reusability, and after five cycles the degradation efficiency could still be maintained beyond 92%. The superior photocatalytic performance on the degradation of organic dyes suggested that the flower-like MgO was a promising candidate for environmental remediation.