Enhancement of Heat and Mass Transfer in the DCMD Process Using UV-Assisted 1-Hexene-Grafted PP Membranes.

The two main challenges for industrial application of membrane distillation (MD) are mitigation of temperature polarization and reduction of high-energy consumption. Despite the development of advanced materials and the configuration improvements of MD units, membrane surface modification is still one of the alternatives to overcome temperature polarization and improve membrane performance. This work reports a novel and simple method to modify the physical and chemical properties of the polypropylene membrane in order to improve its performance in direct contact membrane distillation (DCMD). The membrane was grafted by polymerization with 1-hexene, UV irradiation, and benzophenone as a photoinitiator. A grafting degree of up to 41% was obtained under UV irradiation for 4 h. The performance of the modified membrane in DCMD was evaluated at different temperatures and salt concentrations in the feed. First, it was found that there was an increase of the vapor permeate flux in the MD process within the range of tested temperatures and salt concentrations. The results were analyzed in terms of the physical properties of the membrane, the transport phenomena, and the thermal efficiency of the process. Theoretical analysis of the results indicated that grafting increased the transfer coefficients of mass and heat of the membrane. Hence, it improved the membrane performance and the thermal efficiency of the DCMD process.

Al/Cu-PILC as a Photo-Fenton Catalyst: Paracetamol Mineralization.

Pillared clays have shown to effectively catalyze the photo-Fenton process without the necessity of acidic conditions, which is a very attractive feature from the perspective of environmentally friendly processes, especially when high natural abundance of chemical elements are incorporated. In this work, the catalytic activity of Al/Cu interlayered pillared clays for the degradation and mineralization of paracetamol through a photo-Fenton-like process was investigated. Al/Cu-pillared clays were prepared by adding ane Al/Cu pillaring solution to a bentonite suspension. X-ray diffraction (XRD) confirmed the enlargement of the interlayer space of the clay provoked by the pillaring process and Al and Cu species in the prepared samples were verified by atomic absorption spectroscopy (AAS). The specific surface area of pure bentonite was 2-fold increased after the Al/Cu pillaring process. A synthetic paracetamol solution with an initial concentration of 100 ppm was prepared for the assessment of the activity of the prepared materials. Different catalyst concentrations were tested (0.2, 0.5, 0.75, and 1 g L-1) and the complete removal of paracetamol was achieved in all cases, but the highest mineralization rate (69.8 mg total organic carbon (TOC) gcat -1 h-1) corresponds to the catalyst loading of 0.5 g L-1. An ultraviolet-C (UVC) light source was employed, and no adjustment of the pH to acidic conditions was needed to achieve these results. Liquid chromatography coupled to mass spectroscopy (LC-MS) was employed to identify the reaction intermediates of paracetamol degradation. A proposed pathway for the oxidation of paracetamol molecule is presented. The effect of Cu content in the pillared clay and the stability and reusability of the catalyst were also assessed. The kinetic constants of paracetamol removal were 0.2318 and 0.0698 min-1, under photo-Fenton and UV + H2O2 processes, respectively.

New material for arsenic (V) removal based on chitosan supported onto modified polypropylene membrane.

This paper presents a new material easily synthesized and with low cost, with the possibility of remove arsenic and the potential capability for the remediate water bodies. In this work, the efficiency in removing arsenic of the chitosan, supported onto modified polypropylene membrane, was studied using an aqueous As(V) solution of 0.4 mg/L, achieving a removal efficiency of 75%, which corresponds to an adsorption capacity of 0.031 mg/g. The As(V) adsorption depends on pH and the degree of chitosan grafting on the polypropylene membrane. A pseudo-second-order equation describes the adsorption of the membrane, classifying it as a chemisorption process. The chitosan supported on the membrane was characterized by the analysis of wettability, FT-IR-ATR, SEM-EDS, XRD powder, and surface charge. The As ions coordinate to the chitosan polar groups, allowing their removal from the aqueous solution.

Biodiesel Production from Waste Cooking Oil Catalyzed by a Bifunctional Catalyst.

The objective of this study was to prepare bifunctional catalysts based on iron and CaO and test them in the biodiesel production using waste cooking oil (WCO) as feedstock. Two iron precursors were studied, Fe2O3 and Fe(NO3)3·9H2O. The identified crystalline phases were Ca2Fe2O5 and CaFeO3. Surface morphology and textural properties (distribution of active species, specific surface area, size, and pore volume) were also analyzed. Additionally, thermal stability was studied and 800 °C was established as the optimum calcination temperature. The density of both acidic and basic sites was higher with the catalyst prepared with Fe2O3 than with that prepared with Fe(NO3)3·9H2O. The latter, however, leads to reach equilibrium in half of the time than with the former. This was ascribed to the ratio of acidic to basic sites, which is higher with the catalyst prepared with the precursor salt. This ratio not only affects the overall cost of the process by affecting the time at which equilibrium is reached but also by dictating the methanol/oil molar ratio at which the equilibrium is reached sooner. The prepared bifunctional catalyst allowed us to produce biodiesel with 90% of methyl ester content at atmospheric pressure, reaction temperature of 60 °C, reaction time of 2 h, with 12:1 M ratio of methanol/WCO, 10 wt % of Fe over CaO, and a catalyst loading of 5 wt %. This catalyst can be used at least 3 times. The so-obtained biodiesel met the European norm EN-14214 regarding viscosity and density.

Electron paramagnetic resonance study of hydrogen peroxide/ascorbic acid ratio as initiator redox pair in the inulin-gallic acid molecular grafting reaction.

Gallic acid (GA) was grafted onto inulin using the free radicals method, generated by the hydrogen peroxide/ascorbic acid (H2O2/AA) redox pair. Molar ratios of H2O2/AA at 9, 20, 39 and 49 were evaluated by Electron Paramagnetic Resonance in order to find the effect of the oxidation of the inulin and the efficiency in the inulin-gallic acid grafting (IGA). The highest concentration of the inulin macro-radical was obtained with H2O2/AA molar ratios of 20 and 49 with the removal of a hydrogen atom from a methyl group of the inulin fructose monomers. The highest grafting ratio (30.4 mg GA eq/g IGA) was obtained at 9 M of H2O2/AA. UV-Vis, FT-IR-ATR and XDR results confirmed a successful IGA grafting. The efficiency of the grafting reaction depends on the concentration of the macro-radical, it depends on the molar ratio of H2O2/AA, being affected by simultaneous reactions between components of the mixture (H2O2, AA, inulin, GA and eventually atmospheric oxygen) as well.