Degradation of antipyrine in water with activated persulfate aided with biochar of olive pomace.

The degradation of antipyrine (AP) in water has been studied using persulfate activated with biochar obtained from gasification of olive pomace (BC) combined with ferric salts in the presence of UV-A radiation. Firstly, the adsorption of AP on biochar was evaluated. The data were adjusted using various kinetic models verifying that AP adsorption on BC occurs in three stages and follows pseudo-second order kinetics. Degradation tests show that the presence of iron or persulfate (PS) in binary systems with BC produces increases AP degradation when no radiation is used, reaching 75.7 % due to the ability of BC to donate electrons. On the other hand, addition of PS showed an increase in efficiency in the presence of BC (up to 79%). For ternary systems the best result was found when UVA/PS/Fe was used (100% of AP degradation in 30 min). The addition of UV-A radiation to the BC/PS system improves the degradation of the contaminant by only 6.7%, while the presence of iron in the studied conditions does not cause any improvement. A Central Composite Factorial Design of experiments was used to optimize the UVA/BC/PS/Fe system, leading to an 89.3% AP degradation rate in 90 min (k = 0.0134 min-1) under optimal conditions ([Fe(III)] = 10 mg/L, [PS] = 379 mg/L, [BC] = 500 mg/L). Although the best results were obtained for the UVA/PS/Fe process without BC, systems based on BC/PS can be considered as an alternative in cloudy days or when simple processes are selected due to economical/technical reasons.