Controlled synthesis of Cu₂O microcrystals in membrane dispersion reactor and comparative activity in heterogeneous Fenton application

A surfactant-free approach is proposed to fabricate various-shaped Cu₂O particles with good uniformity by ceramic membrane dispersion. Glucose reduced cupric salt and precipitated Cu₂O (dimension ca. 1 μm and crystal size 18.5 nm) whose homogeneity was distinctly improved by distributing glucose solution through the ceramic mesoporous membrane. Particle shape including cube, sphere-like, octahedron and eight-pod was controlled kinetically by changing the concentration of sodium carbonate and sodium citrate with constant copper concentration. Morphologic transformation mechanism was studied with diffraction intensity ratio of (111)/(100) crystal planes. Micro-cubes formed at low pH and octahedral ones formed at high pH since crystal facet (111) is more stable than (100) with increased alkalinity. At the same pH, eight-pod grains were formed instead of cubes by adding citrate anions. Cu₂O powders in octahedral shape was of the highest catalytic activity to degrade the organic pollutants in a heterogeneous Fenton reaction. CODs in an industrial pulp wastewater was eliminated from initial value 133 mg/L as low as to 26 mg/L. Reduction rate of CODs in water by the octahedral Cu₂O was 80% while the commercial Cu₂O was only 30%.