Hybrid Biochar/Ceria Nanomaterials: Synthesis, Characterization and Activity Assessment for the Persulfate-Induced Degradation of Antibiotic Sulfamethoxazole

Biochar from spent malt rootlets was employed as the template to synthesize hybrid biochar-ceria materials through a wet impregnation method. The materials were tested for the activation of persulfate (SPS) and subsequent degradation of sulfamethoxazole (SMX), a representative antibiotic, in various matrices. Different calcination temperatures in the range 300–500 °C were employed and the resulting materials were characterized by means of N2 adsorption and potentiometric mass titration as well as TGA, XRD, SEM, FTIR, DRS, and Raman spectroscopy. Calcination temperature affects the biochar content and the physicochemical properties of the hybrid materials, which were tested for the degradation of 500 μg L−1 SMX with SPS (in the range 200–500 mg L−1) in various matrices including ultrapure water (UPW), bottled water, wastewater, and UPW spiked with bicarbonate, chloride, or humic acid. Materials calcined at 300–350 °C, with a surface area of ca. 120 m2 g−1, were the most active, yielding ca. 65% SMX degradation after 120 min of reaction in UPW; materials calcined at higher temperatures as well as bare biochar were less active. Degradation decreased with increasing matrix complexity due to the interactions amongst the surface, the contaminant, and the oxidant. Experiments in the presence of scavengers (i.e., methanol, t-butanol, and sodium azide) revealed that sulfate and hydroxyl radicals as well as singlet oxygen were the main oxidative species.

The use of Potentiometric Mass Titration (PMT) technique for determining the acid-base behavior of activated sludge

<div> <p>Activated sludge is a biological floc composed of microorganisms, organics, and inorganics and plays an important role in wastewater treatment. The pH of an activated sludge suspension determines the acid &ndash; base behaviour and the charge of the microorganisms in water. In the present study, the determination of acid &ndash; base behaviour of activated sludge was performed using microelectrophoresis and Potentiometric Mass Titrations (PMT). For activated sludge that is a complicated biological system, direct microelectrophoresis is not a suitable method for the determination of its ζ-potential. This method leads to a variety of isoelectric point (iep) values due to the presence of different microorganisms in activated sludge. On the contrary, the PMT method used for the first time for activated sludge can provide the overall point of zero charge (pzc) value that is 8.2. In addition, a simple methodology is proposed for the quantitative determination of the overall solid charge as a function of solution pH, which requires only (a) the titration curves of an electrolyte suspension and of the blank electrolyte solution and (b) the calculation of the H⁺ ions consumed for the above titration curves.&nbsp;</p> </div> <p>&nbsp;</p>

New carbon from low cost vegetal precursors: acorn and cypress cone

Thermal-treated carbons from acorn and cypress cone were prepared and characterized. The uptakes of heavy metal ions (Ag+, Cd2+ and Cr+3) and organics (phenol, methylene blue and sodium dodecylbenzenesulfonate) from aqueous solution have been studied. Effects of activation by HCl and HNO3 acids on the sorption properties of these carbons were investigated by mass titration, sorption isotherms, IRS, SEM and XRS. The models of Langmuir and Freundlich do not represent our sorption data very well. An earlier proposed empirical correlation is applied successfully to carry out a parameter of comparison between the studied carbons. The acidic treatment changes the surface chemical properties of the two thermal-treated carbons lowering their sorption performances. The carbons show good capacities to uptake metals, phenol and methylene blue, but sodium dodecylbenzenesulfonate is removed from its solutions to minor extent. The up-taking properties are found similar to those of two worldwide used commercial grade carbons.

The Effect of Sulphate Doping on NanosizedTiO2andMoOx/TiO2Catalysts in Cyclohexane Photooxidative Dehydrogenation

The effect of sulphate doping of titania in promoting activity and selectivity ofMoOx/TiO2catalysts for the cyclohexane photooxidative dehydrogenation has been investigated in a gas-solid fluidized bed reactor. Sulphate and/or molybdate-modified titania catalysts were prepared by incipient wet impregnation of nanosized (5–10 nm crystallite size) samples. At 60% of titania surface coverage byMoOx, sulphate surface density was obtained up to 19μmol/m2without formation ofMoO3. The catalysts were characterized byN2adsorption-desorption at−196∘C, micro-Raman and UV-visible reflectance spectroscopy, thermogravimetric analysis coupled with mass spectroscopy (TG-MS), and mass titration. Unsulphated and sulphated titania are both active in cyclohexane total oxidation, but sulphate doping of titania has a detrimental effect on the reaction rate. On Mo-based catalysts, polymolybdate species enabled sulphated titania to convert cyclohexane to benzene (99% selectivity) and cyclohexene, reducing at zero the formation ofCO2. Cyclohexane conversion to benzene is almost linearly dependent on sulphate surface density, resulting in enhanced yield to benzene. The enhanced photooxidative dehydrogenation activity and benzene yield by sulphate doping could be attributed to the increase of surface acidity and, as a consequence, of cyclohexane adsorption.