Spent activated carbon (SAC) must either be disposed of at a landfill or regenerated and reused in industries. Regeneration of SAC is a more preferable option as it can cut down replacement and disposal cost as well as reduce secondary pollution. Chemical regeneration is more suitable and economically feasible option for small-scale industrial application as compared to thermal regeneration. In this study, SAC is regenerated using sodium hydroxide (NaOH) solution and hot water. The aim of this study is to evaluate the effectiveness of NaOH and hot water regeneration of SAC. The optimal regeneration condition for SAC was determined and the regeneration performance was assessed by iodine and methylene blue (MB) adsorption test. Finding shows the optimal regeneration condition of carbon regeneration is 15 mL of 6 N of NaOH solution per g of carbon with 30 min of contact time. The estimated surface area, micropore volume, and total pore volume of batch and column regenerated SAC were 899.1 m²/g, 0.8702 cm³/g, 0.9521 cm³/g; and 849.0 m²/g, 0.8519 cm³/g, and 0.9450 cm³/g, respectively. The regeneration efficiency of regenerated SAC is comparable to fresh activated carbon with regeneration efficiency more than 90% in iodine adsorption test and 98% in MB adsorption test.

The present study focusing on the performances of advanced oxidation process by using ozonation method towards Methyl Orange based on the efficiency of colour removal and Chemical Oxygen Demand (COD) removal. Factorial design with response surface methodology (RSM) was used to evaluate the interaction between operational conditions, such as pH, initial concentration, contact time and persulfate dosage to obtain the optimum range conditions using a semi-batch reactor. The range of independent variables investigated were pH (3-11), initial concentration (100-500mg/L), contact time (10-50min) and persulfate dosage (20-100mM) while the response variables were colour removal and COD removal of Methyl Orange. The experimental results and statistical analysis showed all the parameters were significant. Thus, from this findings, optimization of operational conditions that had been suggested from the ozone/persulfate RSM analysis were (pH 3, 100 mg/L, 50min, 60mM) that would be produced 99% Colour Removal and 80% COD Removal and help in promoting an efficient ozonation process. The effect list data that showed the most contributed effects to increase the percentages of colour removal were pH and persulfate dosage whereas the contact time and initial concentration had the highest positive effects on the COD removal. Other than that, the interaction between pH, contact time and persulfate dosage were found to be the most influencing interaction. Therefore the least influencing interaction was interaction between persulfate dosage and pH. In this study, the correlation coefficient value R² for colour removal and COD removal of Methyl Orange were R²= 0.9976 and R²= 0.9924 which suggested a good fit of the first-order regression model with the experimental data.

The degradations characteristic of azo dye Reactive Green 19 (RG19) was investigated using advanced oxidation process (AOPs). It was evaluated based on colour and chemical oxygen demand (COD) removal. The effect of operational parameters such as initial dye concentration, initial dosage of hydrogen peroxide (H₂O₂), contact time, and pH was also being studied. The samples were treated by ozonation (O₃) and peroxone O₃/H₂O₂process. Advanced oxidation processes (AOPs) involve two stages of oxidation; firstly is the formation of strong oxidant and secondly the reaction of organic contaminants in water. In addition, the term advanced oxidation is referring to the processes in which oxidation of organic contaminants occurs primarily through reactions with hydroxyl radicals. There are several analyses that use to determine the efficiency of the treatment process, which are UV-Vis absorption spectra, COD, Fourier Transform Infrared (FT-IR), and pH. The results demonstrated that the ozone oxidation was efficient in decolourization and good in mineralization, based on the reduction of colour and COD. Additionally, results indicate that H₂O₂is able to perform better than ozonation in order to decolourize the dye wastewater with 0.5 mL H₂O₂/L dye dosage of H₂O₂at different initial concentration, initial pH, with contact time.