A supported copper catalyst was used as a catalyst for the decomposition of organic dyes using a commercial chlorinating agent. The catalytic process achieved complete decomposition in only 2 min. Different catalyst to dye concentration ratios is studied to determine the optimal conditions. The catalyst is fully characterized using XRD, SEM, and EDX analysis.
The removal of organic and inorganic pollutants is an aim shared by many researchers throughout the world [
This study reports the removal of organic dye (pollutants) with a system consisting of a 5% solution of sodium hypochlorite (commercial grade), oxygen gas, and a supported copper oxide catalyst to generate singlet oxygen.
Methyl orange (Merck), sodium hypochlorite solution (commercial), oxygen gas (99.99%), aluminum hydroxide (Merck), and copper nitrate trihydrate (Merck) were used in these experiments.
First, aluminum hydroxide was calcined at 550°C for 3 hours to convert it into Al2O3. Copper was loaded as copper nitrate (20%) on the resulting gamma alumina by impregnation with stirring for 2 h and then dried and calcined at 450°C for 3 hours.
Oxygen was introduced to a 0.5 mL solution of 5% sodium hypochlorite at 100 ppm from methyl orange by passing oxygen at 20 mL/min in an open system. Copper oxide catalyst was added (0.5 g), and samples from methyl orange were collected and separated by centrifuge at several time points for analysis. For comparison, the same reaction was performed with and without catalyst and with and without oxygen.
X-ray diffractograms of the samples under investigation were collected using a Bruker D8 Advance instrument with CuK
Scanning electron microscopy (SEM) images were collected and EDX analysis was performed using a JXA-840 Electron Probe Micro Analyzer (JEOL).
Organic carbon content was measured using a Multi N/C total organic carbon measurement instrument (Analytik Jena, model 2100/2100 S).
The XRD patterns of the supported CuO catalyst over alumina are shown in Figure
XRD of CuO catalyst deposited on alumina.
Figure
SEM of CuO on alumina.
EDX spectra of CuO agglomerates.
Figure
Comparison of the catalytic decomposition activity of catalyst with oxygen only, chlorate solution with oxygen, and catalyst with oxygen and chlorate.
The previous results can be explained in light of the mode of decomposition of the dye. Passing oxygen without chlorate, even in the presence of a catalyst, does not induce decomposition because molecular oxygen is stable under these conditions, and it is very difficult to decompose the dye at room temperature.
In the presence of chlorate solution (5% sodium hypochlorite), the decomposition will occur according to the following equation:
Figure
Effect of the amount of catalyst on the decomposition of the dye.
The following conclusions can be drawn from the research presented previously. The system of a copper catalyst, a solution of commercial chlorate, and any organic dye pollutant could be effective in the decomposition of organic pollutants. The aforementioned system can be easily scaled up at low cost to achieve effective pollutant removal. The decomposition followed a free-radical reaction mechanism and produced singlet oxygen.