Bulk production of porous TiO2 nanowires by unique solvo-plasma oxidation approach for combating biotic and abiotic water contaminants

Pure, porous titania nanowires (TiO₂-pNW) are produced in bulk amount (~?250 kg/day, reaction time scale?<?1 min) using a unique solvo-plasma oxidation method utilizing microwave plasma with the potential of easy scale up. The prepared nanowire is found to be efficient towards both biotic disinfection and destruction of various abiotic contaminants in wastewaters. In terms of organic contaminants, the TiO₂-pNW is tested for destruction of Rhodamine B (RhB) dye, tetracycline (TC) antibiotic, and diclofenac (DFC) and caffeine (CAF) drugs. In the case of biotic contaminants, the disinfection of E. coli bacteria is demonstrated. In all of the studies, the photocatalytic performance of anatase TiO₂-pNW is compared to that of commercially available P25 nanoparticles (TiO₂-P25), both in the presence and absence of ozone. The excellent photoactivity exhibited by TiO₂-pNW is a result of low recombination rate of electron–hole pair owing to the spatial separation of electrons and holes within the photoexcited nanowires. Moreover, the scavenger experiments and experiments involving ozone reveal that electron transfer and/or presence of dissolved oxygen are the major limiting factors for both porous titania nanowires and P25 spherical powder under UV exposure with photocatalytic activity towards pollutant degradation.

     

Alternative for the Treatment of Leachates Generated in a Landfill of Norte de Santander–Colombia,by Means of the Coupling of a Photocatalytic and Biological Aerobic Process

In the present study, the use of heterogeneous photocatalysis TiO2/UV coupled to an activated sludge reactor was evaluated as an alternative treatment for the leachate coming from a Landfill, located in Cucuta (Colombia). TiO₂ (Degussa P-25) between 100 and 600 mg.L^?1 was used as a catalyst, semi-continuous type reactors for the photocatalysis, a batch for the biological stage, UV light with accumulated energies from 20 to 60 kJ.L^?1 were also used, a constant concentration of H₂O₂ was used as an adjuvant in all tests. The research consisted of four main phases: leachate characterization, biological treatment, optimization of photocatalytic and AOP-biological coupling. For the optimization of the photocatalytic step, an experimental design was carried out through the statistical program Statgraphics Centurion XV of factorial type 3^2 (3 levels 2 variables), modeling the results by means of a response surface, the variables of the pH and the concentration of the catalyst were included, having this as input for the response of interest the percentage (%) of DOC removal. The biological process itself provided a removal of 38 and 24% for COD and DOC, respectively. The AOP-biological coupling provided a removal of 68 and 76% in terms of COD and DOC, respectively. Thus, the coupling significantly improves the overall efficiency of the process by more than 50%, which represents a promising improvement compared to the removal of organic matter for the treatment of the same type of water using only the biological process. The results show a viable alternative for the treatment of leachate because higher removal levels are achieved in residence times, which are considered shorter than the ones in conventional processes.

     

Evaluation of Caffeine Degradation by Sequential Coupling of TiO2/O3/H2O2/UV Processes

Topics in Catalysis - This study provides new insight into the implementation and synergy effect of coupling in sequences of the photocatalysis ([TiO2-UVC]), ozone (O3) and hydrogen peroxide (H2O2)...     

Treatment of vinasses by electrocoagulation–electroflotation using the Taguchi method

Taguchi method has been applied in the treatment of vinasse from distillery for assess the performance of the process of electrocoagulation–electroflotation in the removal of total solids, turbidity and total organic carbon (TOC). The variables of study were initial pH, current density, concentration of hydrogen peroxide and material of the electrodes.We obtained removals of 50%, 89% and 25% for total solids, turbidity and total organic content, respectively, and 61% removal of chemical oxygen demand (COD). Fourier Transform Infrared (FTIR) has been used to identify possible compounds that are formed on the electrodes.     

Treatment of Agricultural Wastewater with Chlorpyrifos by Coupling of Heterogeneous Photocatalysis and Anaerobic Biological Process

Topics in Catalysis - Treatment of wastewater with Chlorpyrifos content using heterogeneous photocatalysis was evaluated, for which a compound parabolic collector (CPC) was used, under different...