Sulphate removal in silica sludge via mixtures of hydrogen peroxide and hydrochloric acid solution / Zuraini Kerya

Solid waste disposal becomes an increasingly serious problem due to rapid growth in industrial sector. Most of the industrial solid wastes are classified as scheduled waste, which are highly contaminated with heavy metals and toxic compounds. Scheduled waste must be disposed according to the procedures laid in the Environmental Quality Act 1974 in order to ensure health and safety of the public, nature and its habitat. Sulphate is one of the chemical compounds, which produces toxic gas, hydrogen sulphide during biological reduction process by organisms. The focus of this study is to remove the sulphate compound from industrial solid waste, i.e. silica sludge. The characteristics of silica sludge were identified before and after treatment process. The results show that the silica sludge contains more than 6% of sulphate. Under a laboratory scale, the research involves identifying the effectiveness of chemicals such as hydrogen peroxide and hydrochloric acid on the desulphurisation process. A different concentration of chemicals, reaction times, temperature, and mixture ratio were applied to investigate the best condition for desulphurisation process. The best condition achieved for mixture of 10% HCI and 6% H2O2, at ratio 70 to 30 at reaction temperature 100°C with reaction time 3 hours. About 96.6 % of sulphate was removed from scheduled waste. The weight percent of sulphate removed from silica sludge increased with the increasing of temperatures and reaction times. At the same time the treatment successfully removed heavy metals contains in silica sludge. All the results were further analysed with the usage of the TCLP Test, X-ray Diffraction (XRD) and Fourier Transform Infra-red (FTIR) which confirms the reduction of sulphate and heavy metals after desulphurisation with HCI and H2O2.