Influence of processing conditions on the synergism between UV irradiation and chlorine toward the degradation of refractory organic pollutants in UV/chlorine advanced oxidation system

Removal of persistent textile dyes from wastewater by Fe(ii)/H2O2/H3NOH+ integrated system: process performance and limitations

“…Amounts removed at C 0 = 40 μM became 11.2 and 30.4 μM for Fenton and Fenton-H 3 NOH + , respectively (ratio ∼2.71). This trend, which was reported earlier for the degradation of different dyes by different AOPs, 27,38–40,46 clearly shows the positive effect of operating with a high BF concentration on its degradation efficiency, which is ascribed to the increased probability of oxidant attacks (hydroxyl radicals) upon BF molecules when the latter exist at a higher level. Besides, even though the dye removal kinetics in all Fenton-HA systems decrease exponentially (seeming to follow first-order kinetics), the first-order kinetics law is not applicable because the plot of the initial degradation rate of the dye versus its initial concentration (Fig.…”

“…Different oxidants/species have been found to perform a similar role in several degradation situations involving various cOH or SO 4 c À -based AOPs. 3,27,[35][36][37][38][39][40][41] Consequently, an excessive amount of hydroxylamine (>0.5 mM in our case) should be avoided for the best performance of the Fe(II)/ H 2 O 2 /H 3 NOH + integrated process. To conrm the above enhancement/quenching mechanism of NH 3 OH + toward radical generation in the Fe(II)/H 2 O 2 system, additional experimental evidence was added by analyzing the Fe(III) production kinetics in the presence of low (0.01, 0.1 mM) and excess amounts of H 3 NOH + (1 mM) and comparing the obtained evolution with that achieved at 0.5 mM (i.e., the optimal HA concentration, which provided the best improvement in Fe(II)/H 2 O 2 efficiency, Fig.…”

“…Different oxidants/species have been found to perform a similar role in several degradation situations involving various ˙OH or SO 4 ˙ − -based AOPs. 3,27,35–41 Consequently, an excessive amount of hydroxylamine (>0.5 mM in our case) should be avoided for the best performance of the Fe( ii )/H 2 O 2 /H 3 NOH + integrated process.…”

“…This behavior has been widely reported for a variety of degradation cases involving AOPs. 3,35,37,38,40,41 Consequently, iron( ii ) and H 2 O 2 concentrations should be applied at optimized doses so as not to restrict the efficiency of the Fe( ii )/H 2 O 2 /H 3 NOH + integrated process.…”

“…This behavior has been widely reported for a variety of degradation cases involving AOPs. 3,35,37,38,40,41 Consequently, iron(II) and H 2 O 2 concentrations should be applied at optimized doses so as not to restrict the efficiency of the Fe(II)/H 2 O 2 /H 3 NOH + integrated process. The Fenton-H 3 NOH + process is more efficient than the Fenton process over an extended interval of C 0 (10-40 mM), as depicted in Fig.…”