M.A. Ferro-García

Pharmaceuticals as emerging contaminants and their removal from water. A review

The main objective of this study was to conduct an exhaustive review of the literature on the presence of pharmaceutical-derived compounds in water and on their removal. The most representative pharmaceutical families found in water were described and related water pollution issues were analyzed. The performances of different water treatment systems in the removal of pharmaceuticals were also summarized. The water treatment technologies were those based on conventional systems (chlorine, chlorine dioxide, wastewater treatment plants), adsorption/bioadsorption on activated carbon (from lotus stalks, olive-waste cake, coal, wood, plastic waste, cork powder waste, peach stones, coconut shell, rice husk), and advanced oxidation processes by means of ozonation (O₃, O₃/H₂O₂, O₃/activated carbon, O₃/biological treatment), photooxidation (UV, UV/H₂O₂, UV/K₂S₂O₈, UV/TiO₂, UV/H₂O₂/TiO₂, UV/TiO₂/activated carbon, photo-Fenton), radiolysis (e-Beam, ⁶⁰Co, ¹³⁷Cs. Additives used: H₂O₂, SO₃²⁻, HCO₃⁻, CH₃₋OH, CO₃²⁻, or NO₃⁻), and electrochemical processes (Electrooxidation without and with active chlorine generation). The effect of these treatments on pharmaceutical compounds and the advantages and disadvantages of different methodologies used were described. The most important parameters of the above water treatment systems (experimental conditions, removal yield, pharmaceutical compound mineralization, TOC removal, toxicity evolution) were indicated. The key publications on pharmaceutical removal from water were summarized.

Adsorption of zinc, cadmium, and copper on activated carbons obtained from agricultural by-products

Abstract Adsorption studies of Zn2+, Cd2+, and Cu2+ from aqueous solutions at 293 K and 313 K on three activated carbons are reported. These carbons were obtained by activation of almond shells, olive stones, and peach stones by heating in CO2 at 1123 K. From these isotherms some adsorption parameters have been determined. The influence of the solution pH on the adsorption processes has been studied. The extent of adsorption in the presence of Cl−, CN−, SCN−, or EDTA has been also investigated. The adsorptive behaviour of these activated carbons is explained on the basis of their chemical nature and porous texture.

Regularities in the temperature-programmed desorption spectra of CO2 and CO from activated carbons

Temperature-programmed desorption (TPD) spectra of CO and CO2 have been obtained under vacuum or helium flow with activated carbons from different origins and oxidized in various ways. In particular, a special form of TPD, called Intermittent TPD, has been applied to one of the carbon samples (prepared from almond shells and oxidized with nitric acid) in order determine the variation of the apparent activation energy of desorption Ed as the coverage of the surface decreases. Regularities appeared in the set of results obtained: There are common features in TPD profiles of carbons from different origins and histories. This finding is confirmed by a re-examination of numerous CO and CO2 spectra found in the literature, including results obtained under ultra-vacuum. These regularities are interpreted by the existence of the same superficial entities (various oxygen groups with different environments).

Adsorption of p-nitrophenol on an activated carbon with different oxidations

An activated carbon prepared from olive stones has been modified through oxidation by nitric acid or sodium hypochlorite. These treatments introduced large amounts of oxygen groups, which were characterized by mass-spectrometry, temperature-programmed desorption (DTP–MS). Both CO2- and CO-evolving groups were created by these oxidation treatments. A part of these oxidized samples was then outgassed under vacuum up to 823 K in order to remove most of the CO2-evolving groups from their surface. Oxidized samples have a smaller surface area than the original sample. The subsequent partial outgassing increases the surface area which, however, does not reach the value it had before oxidation. p-Nitrophenol (PNP) adsorption isotherms from aqueous solutions were determined at 298 K for the original, oxidized, and partly outgassed samples. The results confirm the presence of an intermediate plateau at low equilibrium PNP concentration (at about 10 mg/l). The relative effects of textural versus surface chemistry on PNP uptakes are then discussed. The presence of CO-evolving groups showed no influence on PNP uptakes. The conclusion is that models in which carbonylic groups are basic adsorption sites for substituted phenols can be ruled out for the entire isotherm of PNP obtained with the original carbon. These models are also unlikely for PNP adsorption on oxidized and partly outgassed samples.

Removal of nitroimidazole antibiotics from aqueous solution by adsorption/bioadsorption on activated carbon.

The objective of the present study was to analyse the behaviour of activated carbon with different chemical and textural properties in nitroimidazole adsorption, also assessing the combined use of microorganisms and activated carbon in the removal of these compounds from waters and the influence of the chemical nature of the solution (pH and ionic strength) on the adsorption process. Results indicate that the adsorption of nitroimidazoles is largely determined by activated carbon chemical properties. Application of the Langmuir equation to the adsorption isotherms showed an elevated adsorption capacity (X(m)=1.04-2.04 mmol/g) for all contaminants studied. Solution pH and electrolyte concentration did not have a major effect on the adsorption of these compounds on activated carbon, confirming that the principal interactions involved in the adsorption of these compounds are non-electrostatic. Nitroimidazoles are not degraded by microorganisms used in the biological stage of a wastewater treatment plant. However, the presence of microorganisms during nitroimidazole adsorption increased their adsorption on the activated carbon, although it weakened interactions between the adsorbate and carbon surface. In dynamic regime, the adsorptive capacity of activated carbon was markedly higher in surface water and groundwater than in urban wastewaters.

Synthesis and textural characteristics of organic aerogels, transition-metal-containing organic aerogels and their carbonized derivatives

Abstract Four organic aerogels were prepared by the sol-gel method from polymerization of resorcinol with formaldehyde catalyzed by Na 2 CO 3 . These aerogels were further pyrolyzed in N 2 in order to obtain their corresponding carbon aerogels, and after that activated with either steam or CO 2 to obtain activated carbon aerogels. Another series of organic aerogels and their pyrolyzed and activated derivatives were prepared without a catalyst or in the presence of Ag, Pd or Pt. All these samples were texturally characterized, which has shown the porous modifications undergone by the aerogels during the pyrolysis and activation processes. The textural characteristics of the transition-metal-containing activated carbon aerogels depend on the nature of the metal. Thus, whereas the sample containing Pt, in a very small amount, had the largest meso and macropore volume (0.822 and 2.982 cm 3 g −1 ) found, those containing either Pd or Ag were essentially microporous.

Thermal regeneration of an activated carbon exhausted with different substituted phenols

The thermal desorption process of phenol, m-aminophenol, p-cresol and p-nitrophenol from an activated carbon has been studied. For this purpose, the activated carbon-phenolic compound system was heated to 1100 K in a He flow following determination of weight loss and the evolution of light gases by a thermobalance and by mass spectrometry, respectively. Results showed that during the heat treatment, part of the phenol evolved from the activated carbon and was deposited at the outlet of the reactor and part underwent degradation reactions to light gases and to a residue that remained on the surface of the activated carbon. Finally, the variation of the adsorption capacity of the activated carbon after several adsorption-regeneration cycles has also been studied.

Influence of the oxygen surface complexes of activated carbons on the adsorption of chromium ions from aqueous solutions : effect of sodium chloride and humic acid

Adsorption of Cr(III) and Cr(VI) on activated carbons from aqueous solutions has been studied. A commercial activated carbon, then treated with HNO3 to introduce surface oxygen complexes, and subsequently heated up to 873 K in N2 to eliminate some of the above complexes, gave the three samples used. Adsorption of both Cr(III) and Cr(Vl) was enhanced by the presence of surface oxygen complexes of acid type on the activated carbon. The effect of the presence of NaCl and humic acid in the chromium solution on the adsorption capacity of the activated carbons has also been studied.

Gamma irradiation of pharmaceutical compounds, nitroimidazoles, as a new alternative for water treatment.

The main objectives of this study were: (1) to investigate the decomposition and mineralization of nitroimidazoles (Metronidazole [MNZ], Dimetridazole [DMZ], and Tinidazole [TNZ]) in waste and drinking water using gamma irradiation; (2) to study the decomposition kinetics of these nitroimidazoles; and (3) to evaluate the efficacy of nitroimidazole removal using radical promoters and scavengers. The results obtained showed that nitroimidazole concentrations decreased with increasing absorbed dose. No differences in irradiation kinetic constant were detected for any nitroimidazole studied (0.0014-0.0017 Gy(-1)). The decomposition yield was higher under acidic conditions than in neutral and alkaline media. Results obtained showed that, at appropriate concentrations, H(2)O(2) accelerates MNZ degradation by generating additional HO(); however, when the dosage of H(2)O(2) exceeds the optimal concentration, the efficacy of MNZ degradation is reduced. The presence of t-BuOH (HO() radical scavenger) and thiourea (HO(), H() and e(aq)(-) scavenger) reduced the MNZ irradiation rate, indicating that degradation of this pollutant can take place via two pathways: oxidation by HO() radicals and reduction by e(aq)(-) and H(). MNZ removal rate was slightly lower in subterranean and surface waters than in ultrapure water and was markedly lower in wastewater. Regardless of the water chemical composition, MNZ gamma irradiation can achieve i) a decrease in the concentration of dissolved organic carbon, and ii) a reduction in the toxicity of the system with higher gamma absorbed dose.

Bioadsorption of Pb(II), Cd(II), and Cr(VI) on activated carbon from aqueous solutions

The bioadsorption of Pb(II), Cd(II), and Cr(VI) using bacteria and activated carbon has been studied. Preliminary studies yielded the chemical and textural characterization of the carbons. The adsorption of bacteria on the activated carbons modified their surface characteristics, reducing the volume of pores and the pH of the point of zero charge, with a resulting increase in the density of the negative charge of their surface. The adsorption of the above metals was studied in both static and dynamic conditions and in the absence and presence of bacteria (Escherichia coli). The presence of bacteria in aqueous solution enhances the adsorption of Pb(II) and Cd(II) and reduces the adsorption of Cr(VI). These results can be explained by changes in the surface charge density of the carbons when bacteria are adsorbed, and by considering the structural and chemical characteristics of the bacterial cell walls. Investigation of the effect of electrolytes on the bioadsorption of these metals showed, in general, a resulting reduction in the amount of metal adsorbed, mainly in the presence of divalent cations. According to the divalent cation bridging theory, these results derive from competition between the Pb(II) or Cd(II) cations and the electrolyte cations for the negatively charged functional groups of extracellular polymeric substances.