The influence of selected variables such as pH of phenol solution, concentration of hydrogen peroxide, concentration and the volume of phenol to be treated was studied to find the degree on the degradation of phenol. The influence of these variables on the degradation of phenol using H2O2 by interpreting the TOC results is presented in the following sections.
3.1 Effect of pH
The phenol degradation with different pH is shown in Figure 3. As it is clearly seen, a higher pH favors the removal of phenol in altered conditions. In Figure 3(a), the phenol was purged in ozone in absence of hydrogen peroxide. The removal rate for the alkaline solution (pH11) at after 40 minutes was at its highest at 7.89%. Direct procedure involves organic …show more content…
These organic acids include oxalic acids, maleic acids, muconic acids and so on[18, 20, 21]. Because of the selective nature of ozone with regard to formed by-products, whereby acidic conditions produce a low TOC removal rate, direct ozonation rarely yields complete mineralization. [22]. Alternatively, strong alkaline conditions provide an important improvement in the oxidation power of ozonation process, which can be attributed to the prevalent indirect process that incorporates the production of OH radicals by ozone decomposition in aqueous solution, especially that which is catalyzed by OH− (i.e. higher pH) shown below in the following …show more content…
This can also be seen by the value of the rate constants where k1 k2. Additionally the process of phenol decomposition by direct ozonation is different than that of indirect ozonation. Degradation of phenol by OH radicals favors the formation of aromatic by products, following the formation of organic acids and thereafter partial mineralization [26]. Because the OH radical is a powerful and unselective oxidant, raising the initial Ph values increased TOC removals. The alkaline environment presented a higher degradation rate for the whole duration of 80 minutes than that of the initial pH (pH8.9) and acidic pH (pH4). Some studies show that the fastest phenol degradation occurred at pH 12.9. Furthermore, the highest COD removal in the study of the treatment of penicillin formulation effluent by ozone process at pH 12. [27] In general, the degradation of phenol always happens by both direct and indirect mechanisms, which are competitive and dependent of process conditions. It has also been observed that radical mechanism is predominant even at neutral pH .[24] However, due to the slow rate of self-decomposition of ozone initiated by OH− ion at neutral pH, it was established that phenolic compounds themselves must be acting as the promoters of the decomposition of ozone and the formation of free radicals
3.1 Effect of pH
The phenol degradation with different pH is shown in Figure 3. As it is clearly seen, a higher pH favors the removal of phenol in altered conditions. In Figure 3(a), the phenol was purged in ozone in absence of hydrogen peroxide. The removal rate for the alkaline solution (pH11) at after 40 minutes was at its highest at 7.89%. Direct procedure involves organic …show more content…
These organic acids include oxalic acids, maleic acids, muconic acids and so on[18, 20, 21]. Because of the selective nature of ozone with regard to formed by-products, whereby acidic conditions produce a low TOC removal rate, direct ozonation rarely yields complete mineralization. [22]. Alternatively, strong alkaline conditions provide an important improvement in the oxidation power of ozonation process, which can be attributed to the prevalent indirect process that incorporates the production of OH radicals by ozone decomposition in aqueous solution, especially that which is catalyzed by OH− (i.e. higher pH) shown below in the following …show more content…
This can also be seen by the value of the rate constants where k1 k2. Additionally the process of phenol decomposition by direct ozonation is different than that of indirect ozonation. Degradation of phenol by OH radicals favors the formation of aromatic by products, following the formation of organic acids and thereafter partial mineralization [26]. Because the OH radical is a powerful and unselective oxidant, raising the initial Ph values increased TOC removals. The alkaline environment presented a higher degradation rate for the whole duration of 80 minutes than that of the initial pH (pH8.9) and acidic pH (pH4). Some studies show that the fastest phenol degradation occurred at pH 12.9. Furthermore, the highest COD removal in the study of the treatment of penicillin formulation effluent by ozone process at pH 12. [27] In general, the degradation of phenol always happens by both direct and indirect mechanisms, which are competitive and dependent of process conditions. It has also been observed that radical mechanism is predominant even at neutral pH .[24] However, due to the slow rate of self-decomposition of ozone initiated by OH− ion at neutral pH, it was established that phenolic compounds themselves must be acting as the promoters of the decomposition of ozone and the formation of free radicals