Experimental optimization of enzymatic and thermochemical pretreatments of bread waste by central composite design study for bioethanol production.

The present study aimed at optimizing the combined effect of enzymatic and thermo-chemical pretreatment hydrolysis of bread waste (BW) for enhancing the yield of reducing sugars (RS). Statistical optimization of enzymatic and thermochemical pretreatment processes was performed using the central composite design (CCD) tool of response surface methodology (RSM) using four process parameters (waste bread ratio, alpha-amylase concentration, temperature and pH) on total sugars yield as response variable. It was found that the optimal conditions for maximally RS yield were at bread ratio of 0.03 g/mL, alpha-amylase concentration of 0.2 mL/L, temperature of 100 °C and pH 5.3. Under these conditions, the yield of RS reached 90%, with bioethanol concentration of about 85.8 g/L after 72 h of batch fermentation. The modified Gompertz equation was used to describe the cumulative bioethanol production. A good agreement was found between simulated and experimental data.

The multiple role of inorganic and organic additives in the degradation of reactive green 12 by UV/chlorine advanced oxidation process.

The impact of various mineral anions, diverse organic substrates and different environmental matrices on the removal of C.I. reactive green 12 (RG12), a refractory textile dye, by UV/chlorine emerging advanced oxidation process (AOP) was performed. The co-exposure of RG12 (20 mg L-1) to UV and chlorine (0.5 mM) at pH 5 produced a strong synergism on the degradation rate. Radical probe technique showed that ●OH and Cl2●- were the main source of the synergistic effect. Bromide, bicarbonate and chloride at small dosage, i.e. 1 mM, enhanced the rate of RG12 degradation, but higher concentrations of these anions quenched the degradation process. Sulphate anions did not alter the degradation rate of the dye, but nitrite quenched it at ∼ 90%. The inhibiting effect of nitrate appeared only at advanced reaction time (>1 min).On the other hand, natural organic matter (NOM) reduced effectively the degradation rate. Besides, SDS surfactant at only 1 µM accelerated the degradation efficiency by ∼12%. However, Tween 80 has shown an insignificant effect, whereas reductions of 10% and 30% were recorded by Triton X100 and Tween 20, respectively. The RG12-degradation rate was not affected in the mineral water, but it was drastically improved in seawater. Conversely, a huge drop in the RG12-degradation efficiency was obtained in the wastewater effluent. UV/chlorine process is highly viable for degrading pollutant in matrices free of NOM. However, the process losses its potential application in matrices riche of NOM.

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.

The synergy of applying UV/chlorine advanced oxidation process (AOP) for the degradation of organic pollutants was usually reported. However, very limited information is available on the influence of processing conditions on the resulted synergism. In this work, C.I. reactive green 12 (RG12), a refractory textile dye, has been selected as a pollutant model to examine the synergism dependence of operational conditions in UV/chlorine AOP. Initial tests conducted with 500 µM of chlorine and 20 mg L-1 of RG12 have resulted in a high synergy index (SI) of 3. Operating conditions sensitively affect the value of SI. This latter increased with increasing initial chlorine and RG12 concentrations up to certain optimums at 500 µM of chlorine and 20 mg L-1 of RG12 and decreased afterward. The best SI value, i.e. 3, was obtained at pH 5, followed by pH 7 (SI = 2.2) and then pH 9-10.5 (SI ~ 2). On the other hand, the synergistic index decreased importantly from 3 at 25 °C to only 1.2 at 55 °C. Finally, by using different radical scavengers, it was found that among various suspected oxidants, only ●OH and Cl2●- play a key role in the synergistic effect between UV and chlorine toward RG12 degradation.

Using photoactivated acetone for the degradation of Chlorazol Black in aqueous solutions: Impact of mineral and organic additives.

This study examined the effect of different mineral and organic additives on the degradation of Chlorazol Black (CB, 25.5 µM) in aqueous media by UV/acetone process. Initially, it was found that acetone (50 mM)-assisted UV irradiation accelerated the CB removal within 30 min to 98% against 34% for the sole UV, presumably due to the implication of methyl radicals in the degradation process as confirmed by O2 saturation and nitrite addition (as CH3-specific scavengers). While NaCl and Na2SO4 have no impact on the degradation kinetics of CB upon UV/acetone process, NaHCO3 and Na2CO3 slightly inhibited it and a relatively more inhibition was observed with NaNO3 and KBr. The degradation performance was somewhat decreased in natural mineral water. On the other hand, ascorbic acid, as free radicals scavenger, at low concentration (0.1 mM) completely quenched the positive effect of acetone confirming the free radical mechanism on CB degradation. Besides, the implication of OH was excluded by adding 2­propanol (up to 50 mM). Furthermore, the slight decrease in CB removal in the presence of sucrose, glucose and humic acid is a clear indication that UV/acetone process is a promising technique for removing organic dyes from environmental samples.

Optimization of the indole photodegradation on supported TiO(2): influences of temperature, concentration, TiO(2) amount and flow rate.

This work describes the photodegradation of aqueous indole solutions by using TiO(2) supported on cellulose fibres. Four parameters were studied: the indole concentration; the TiO(2) amount; the temperature and the flow rate. Central composite experimental design was used to determine the influences of the parameters on the indole degradation percentage. We demonstrate that in our experimental domain the quasi complete degradation of indole is in all cases reached and more interestingly that it is possible to find unique values of TiO(2) amount and flow rate leading to optimised photodegradation of indole in the studied domains of temperature and indole concentration.