Antonio Lopez

2. Sensitized degradation of chlorophenols on iron oxides induced by visible light: Comparison with titanium oxide

Abstract The sensitized photocatalytic degradation of mono-, di- and trichlorophenols on iron oxides aqueous suspensions of α-Fe 2 O 3 and α-FeOOH is reported in detail. The degradation of these compounds followed pseudo-first-order kinetics when α-Fe 2 O 3 was used as photocatalyst. α-FeOOH was found to be inactive for chlorophenols degradation with the exception of 2,4-dichlorophenol (2,4-DCP) where a modest effect was observed. The formation of a surface complex by the chlorophenols with the iron oxide and the solubility of the particular chlorophenol in aqueous solution were observed to be the controlling parameters during the photodegradation. The results obtained with the most active catalyst α-Fe 2 O 3 are compared with TiO 2 . Total mineralization of chlorophenols was observed on TiO 2 while on α-Fe 2 O 3 only partial mineralization was observed. In either case, the intermediates produced in solution during the photodegradation were found to be significantly more biodegradable than the initial compound. For mono-, di- and trichlorophenols the overall photocatalytic degradation was observed to increase in the order: 2,4,6-trichlorophenol (2,4,6-TCP) 3- DCP ) chlorophenol (2- CP) ,4-DCP. The former sequence shows that the recalcitrant 2,4-DCP degrades more rapidly than other chlorophenols tested during this study. The photodegradation of chlorophenols on α-Fe 2 O 3 and TiO 2 proceeds mechanistically through para -hydroxylation of the initial compound as suggested by the intermediates found by high-pressure liquid chromatography HPLC during the course of the degradation.

Nitrogen recovery from a stabilized municipal landfill leachate

The present paper reports the results of an investigation aimed at evaluating the effectiveness of magnesium ammonium phosphate precipitation (MAP), commonly called struvite, for removing ammonia from a mature municipal landfill leachate. MAP precipitation was carried out at laboratory scale by adding phosphoric acid and magnesium oxide as external sources of phosphorus and magnesium, respectively, and regulating the pH at 9.0. The effect of Mg:NH(4):PO(3) ratio was studied. Due to the low solubility of MgO, a low ammonia removal efficiency (i.e. 67%), with a rather high residual concentration, was obtained when the stoichiometric molar ratio was applied. However, by doubling the amount of magnesium oxide (i.e. by using a molar ratio of 2:1:1), ammonia removal efficiency increased up to 95% with a residual concentration compatible with a successive biological treatment. The struvite produced in the present study showed a composition close to the theoretical one. Furthermore, the precipitate was characterized by a heavy metal content much lower than that of typical raw soil, excluding any concern about heavy metal contamination in the case of its use as a fertilizer. The economic analysis of the process showed that ammonia can be removed at a cost of 9.6 euro/kg NH(4)-N(removed). This value can be greatly reduced, however, if the value of the struvite produced is considered.

Quality assessment of bed sediments of the Po River (Italy).

Comprehensive and contemporary evaluations of physical, chemical and toxicological endpoints have been performed on bed sediments of the Po River, the major Italian watercourse. Two extensive sampling campaigns were conducted in summer and winter low-flow conditions. Composite sediment samples were collected from ten reaches of the main river: the first was located in the upper region (ambient control), and the others downstream of the confluences of nine principal tributaries. The two sampling programs were paralleled by contemporary investigations on the macroinvertebrate community. The particle-size composition along the Po River showed a relatively uniform distribution of fine sand, a progressive downstream decrease of coarse sands and a corresponding increase of fine materials. The levels of polychlorinated biphenyls (PCB), polycyclic aromatic hydrocarbons (PAH), extractable organo halides (EOX), Cd, Cr, Cu, Hg, Ni, Pb and Zn were determined in sediment fine particles (< 63 microm), and showed marked changes across the ten river reaches. Their longitudinal trends, as those of organic carbon and total nitrogen, were very similar and largely independent of the survey season. Sediment quality benchmarks were used to evaluate sediment chemistry, and, although the overall level of contamination was from moderate to low, the reaches located downstream of the tributaries Dora Riparia, Dora Baltea, Lambro and Oglio were considered to be at risk. Sediments were tested for toxicity on Oncorhynchus mykiss, Ceriodaphnia dubia, Raphidocelis subcapitata and Vibrio fischeri. The toxicity tests were conducted both with sediment extracts and whole samples. Sediment extracts showed toxic potentials that were consistent with the spatial distribution of contaminants. Whole-sediment toxicity showed moderate/low effects which also included false positives and negatives. Alterations of the macroinvertebrate community were found for many kilometers downstream of Dora Riparia, and with a seasonal dependence, also in other reaches of the Italian river. Principal component analysis (PCA) was used to describe the longitudinal and temporal changes of the Po River, and allowed the selection of the most useful and discriminating indicators.

Oxidative degradation of textile waste water. Modeling reactor performance

Abstract This study reports on the Fenton and photo-assisted Fenton treatment of textile waste waters from nanofiltration of biologically treated secondary textile industry effluents produced in a large scale plant in Northern of Italy. The influence of the hydrodynamic and chemical parameters affecting the degradation of the non-biodegradable residues of textile waters being continuously replaced near the light source were studied in a flow reactor. Cu2++Fe2+/3+-ions mediated oxidation processes under light analogous to the Haber–Weiss cycle were found to be suitable to degrade the recalcitrant part of the textile waters after the initial biological treatment. The optical absorption of the iron-chromophore and the spectral emission of the light source used but not the intensity of the applied light were the most important factors determining the kinetics and efficiency of the applied treatment. A single polynomial exponential expression was constructed for the treatment of the experimental data to make the most economical use of the oxidant, electrical energy and processing time. This approach allowed the prediction of the lowest final TOC values when optimizing the main variables affecting the degradation via phenomenological modeling. Insight is given into the way of handling simultaneously the optimization of five chemical and physical variables intervening in the degradation process by way of a program on a desk computer. As a result the data from the degradation runs were used to evaluate the coefficients of the polynomial exponential expression rendering 2D-contour surface plots. A correlation factor >95% was found between the experimental and the values predicted by the mathematical expression following an exponential decay law.

Effective organics degradation from pharmaceutical wastewater by an integrated process including membrane bioreactor and ozonation.

The enhanced removal of organic compounds from a pharmaceutical wastewater resulting from the production of an anti-viral drug (acyclovir) was obtained by employing a membrane bioreactor (MBR) and an ozonation system. An integrated MBR-ozonation system was set-up by placing the ozonation reactor in the recirculation stream of the MBR effluent. A conventional treatment set-up (ozonation as polishing step after MBR) was also used as a reference. The biological treatment alone reached an average COD removal of 99%, which remained unvaried when the ozonation step was introduced. An acyclovir removal of 99% was also obtained with the MBR step and the ozonation allowed to further remove 99% of the residual concentration in the MBR effluent. For several of the 28 organics identified in the wastewater the efficiency of the MBR treatment improved from 20% to 60% as soon as the ozonation was placed in the recirculation stream. The benefit of the integrated system, with respect to the conventional treatment set-up was evident for the removal of a specific ozonation by-product. The latter was efficiently removed in the integrated system, being its abundance in the final effluent 20-fold lower than what obtained when ozonation was used as a polishing step. In addition, if the conventional treatment configuration is employed, the same performance of the integrated system in terms of by-product removal can only be obtained when the ozonation is operated for longer than 60 min. This demonstrates the effectiveness of the integrated system compared to the conventional polishing configuration.

Biodiesel from dewatered wastewater sludge: A two-step process for a more advantageous production

Alternative approaches for obtaining biodiesel from municipal sludge have been successfully investigated. In order to avoid the expensive conventional preliminary step of sludge drying, dewatered sludge (TSS: 15wt%) was used as starting material. The best performance in terms of yield of fatty acid methyl esters (18wt%) with the lowest energy demand (17MJkgFAME(-1)) was obtained by a new two-step approach based on hexane extraction carried out directly on dewatered acidified (H2SO4) sludge followed by methanolysis of extracted lipids. It was found that sulphuric acid plays a key role in the whole process not only for the transesterification of glycerides but also for the production of new free fatty acids from soaps and their esterification with methanol. In addition to biodiesel production, the investigated process allows valorization of primary sludge as it turns it into a valuable source of chemicals, namely sterols (2.5wt%), aliphatic alcohols (0.8wt%) and waxes (2.3wt%).

The 10 m3 h−1 rim-nut demonstration plant at West Bari for removing and recovering N and P from wastewater

The RIM-NUT, a new ion exchange-precipitation process for removing and recovering ammonium and phosphate ions from wastewater, has been tested on a 10 m3 h−1 demonstration plant for tertiary treatment of West Bari domestic effluent. Natural zeolite clinoptilolite and a porous strong base resin, regenerated in a “closed-loop” fashion with 0.6 M neutral NaCl, ensure ≥90% removal of both nutrient species. Nutrients are precipitated from resin eluates as MgNH4PO4, a premium quality slow-release fertilizer.

Efficient photo-assisted Fenton catalysis mediated by Fe ions on Nafion membranes active in the abatement of non-biodegradable azo-dye

Highly dispersed Fe ions on Nafion membranes are shown to decompose H2O2 with similar kinetics as found for homogeneous solutions containing Fe3+ ions during the photo-assisted Fenton degradation of Orange II, avoiding the drawbacks of the homogeneous treatment.

Peroxymonosulfate-Co(II) oxidation system for the removal of the non-ionic surfactant Brij 35 from aqueous solution.

The non-ionic surfactant Brij 35 was effectively removed from concentrated aqueous solution by the peroxymonosulfate/Co(II) system, using oxone (2KHSO(5)·KHSO(4)·K(2)SO(4)) as a source of peroxymonosulfate. At pH=2.3 and initial Brij 35 concentration in the range 680-2410 mg L(-1), 86-94% removal was achieved after 24 h, using Co(II)=15 μM and oxone=5.9 mM. The effectiveness of removal did not change when initial pH was in the range 2.3-8.2. After five subsequent additions of Co(II) and oxone to the solution, COD and TOC removals increased up to 64% and 33%, respectively. Radical quenching tests confirmed that sulfate radical was the dominant radical species in the system. The main identified by-products from surfactant degradation were: (a) low molecular weight organic acids; (b) aldehydes and formates with shorter ethoxy chain than Brij 35; (c) alcohol ethoxylates carrying hydroxyl groups bonded to ethoxy chain. By-products identification allowed to hypothesize the pathways of Brij 35 degradation.

Solar photo-Fenton degradation of nalidixic acid in waters and wastewaters of different composition. Analytical assessment by LC–TOF-MS

This work assessed the solar photo-Fenton degradation of nalidixic acid (NXA), a quinolone antibacterial agent, in several different aqueous solutions. It has been proven that the composition of the water clearly affects the efficiency of the photo-Fenton process. The presence of chlorine ions induces the concurrence of different mechanisms involving Cl() and Cl(2)(-) radicals, which slow down the process. Up to 35 transformation products (TPs) were identified and their structures characterized by accurate LC-TOF-MS mass measurements during treatment of the different model waters. Photocatalytic degradation was thus observed to proceed mainly through the attack of the hydroxyl radicals on the double bond C((2))C((3)) which induce further ring opening. All the TPs identified persisted after total degradation of NXA. NXA in real pharmaceutical effluent was treated by photo-Fenton as a first stage before biological treatment. As NXA has been demonstrated to be recalcitrant to biological treatment, photo-Fenton treatment of the effluent was continued until its total degradation. Although NXA was efficiently degraded, LC-MS analyses demonstrated that some of the TPs identified after the photo-Fenton treatment were also recalcitrant to biological treatment, persisting after the combined treatment. These results show that analytical assessment of photocatalytic water treatments is essential to assure they are functioning as intended.