Advanced oxidation processes (AOPs) are of special interest in treating landfill leachate as they are the most promising procedures to degrade recalcitrant compounds and improve the biodegradability of wastewater. This paper aims to refresh the information base of AOPs and to discover the research gaps of AOPs in landfill leachate treatment. A brief overview of mechanisms involving in AOPs including ozone-based AOPs, hydrogen peroxide-based AOPs and persulfate-based AOPs are presented, and the parameters affecting AOPs are elaborated. Particularly, the advancement of AOPs in landfill leachate treatment is compared and discussed. Landfill leachate characterization prior to method selection and method optimization prior to treatment are necessary, as the performance and practicability of AOPs are influenced by leachate matrixes and treatment cost. More studies concerning the scavenging effects of leachate matrixes towards AOPs, as well as the persulfate-based AOPs in landfill leachate treatment, are necessary in the future.
Oxidation of p-Cresol was investigated by using ozonation process. The aim of this research is to assess the effectiveness of ozonation on oxidation of micropollutant such as p-Cresol. Ozonation performance was evaluated based on p-Cresol concentration reduction and chemical oxidation demand (COD) reduction. It was found ozonation at pH11 achieved the highest p-Cresol degradation, with 95.8% of p-Cresol reduced and 96.0% of COD reduced, for an initial 50 mgL -1 of p-Cresol. The degradation of p-Cresol could be expressed by second-order of kinetic model. The second-order rate constant k increases as the initial pH increased, but decreases with the increasing of initial p-Cresol concentrations. Besides, the absorption spectra of p-Cresol over ozonation time were analyzed by spectrophotometry. The evolution of absorption spectra of p-Cresol degradation suggests that the oxidation of p-Cresol follows three stages mechanisms with cycloaddition as the first step to produce aromatic intermediates followed by ring-opening reactions, degradation of the intermediates, and subsequently achieved mineralization. ABSTRAKPengoksidaan p-Cresol dikaji dengan menggunakan proses pengozonan. Tujuan penyelidikan ini adalah untuk menilai keberkesanan pengozonan terhadap pengoksidaan pencemar mikro seperti p-Cresol. Prestasi pengozonan dinilai berdasarkan pengurangan kepekatan p-Cresol dan pengurangan permintaan oksigen kimia (COD). Didapati pengozonan pada pH11 mencapai kemerosotan p-Cresol tertinggi dengan 95.8% p-Cresol dikurangkan dan 96.0% COD dikurangkan, untuk awalan 50 mgL -1 p-Cresol pada suhu bilik. Degradasi p-Cresol boleh dinyatakan oleh model kedua kinetik. Pesanan laju pesanan kedua k meningkat apabila pH awal meningkat, tetapi berkurangan dengan peningkatan kepekatan p-Cresol awal. Selain itu, spektrum penyerapan p-Cresol ke atas masa pengozonan dianalisis spektrofotometri. Evolusi spektrum penyerapan degradasi p-Cresol menunjukkan bahawa pengoksidaan p-Cresol mengikuti tiga peringkat mekanisme dengan pensiklotambahan sebagai langkah pertama untuk menghasilkan perantara aromatik diikuti oleh reaksi pembukaan cincin, kemerosotan perantaraan dan seterusnya pemineralan.
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/H2O2 process. 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 H2O2 is able to perform better than ozonation in order to decolourize the dye wastewater with 0.5 mL H2O2/L dye dosage of H2O2 at different initial concentration, initial pH, with contact time.
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