PHOTOCATALYTIC DEGRADTION OF AZO AND RHODAMINE DYES USING NANOSTRUCTURED COPPER (II) OXIDE

ABSTRACT

Organic dye pollutants are sometimes released into the environment with wastewater from

industries which make use of such dyes. In surface water, they contaminate the surrounding

environment while their residue accumulates on land. These chemicals are noted for their

toxicity to living organisms and they can cause cancers in human beings. In this study a

relatively simple, long term and cost effective remedy for dye pollution reduction was

developed; with a focus on the use of semiconductor photocatalysis for the breakdown of the

dye in water. Due to their ease of synthesis, minimal toxicity and cost, copper (II) oxide (CuO)

nanoparticles were used to degrade three commonly used dyes; Methyl Orange (MeO),

Methylene Blue (MB) and Rhodamine B (RhB) which arise from two prominent dye families

(Azo and Rhodamine dyes).

CuO nanoparticles were synthesised following a simple solution method using two copper

precursor salts; hydrated copper sulphate (CuSO4.5H2O) and hydrated copper nitrate

(Cu(NO3)2.3H2O). The CuO was precipitated from a 0.02 M copper salt solution using 1.6 g/L

NaOH pellets. The temperature at which these pellets were added to the copper salt solutions

(25 °C and 60 °C) played a major role in determining the shape and size of the nanoparticles.

The synthesised particles were then characterised using X-Ray Diffraction (XRD), Scanning

Electron Microscopy (SEM), UV-Vis Spectrophotometry, Fourier Transform Infra-Red (FTIR)

spectroscopy and Brunauer Emmett Teller (BET) surface area and porosity analysis. The

synthesised nanoparticles were microporous with sizes ranging from 12 – 13.5 nm and BET

surface areas of 26.8 m2/g, 28.4 m2/g and 49.3 m2/g. The photocatalytic character of the

synthesised particles was assessed in the presence of visible light for 100 minutes at 25-minute

intervals and the overall minimum and maximum degradation efficiency recorded amongst all the samples was 85 % and 99 %.

Keywords: Nanoparticles; Copper Oxide; Photocatalysis; Wastewater; Dye; Degradation