Selective Extraction of Platinum(IV) from the Simulated Secondary Resources Using Simple Secondary Amide and Urea Extractants

The recycling of rare metals such as platinum (Pt) from secondary resources, such as waste electronic and electrical equipment and automotive catalysts, is an urgent global issue. In this study, simple secondary amides and urea, N-(2-ethylhexyl)acetamide, N-(2-ethylhexyl)octanamide, and 1-butyl-3-(2-ethylhexyl)urea, which selectively extract Pt(IV) from a simulated effluent containing numerous metal ions, such as in an actual hydrometallurgical process, were synthesized and achieved efficient Pt(IV) stripping using only water. Comparison of Pt(IV) extraction behavior with a tertiary amide without N–H moieties suggests that the secondary amides and urea extractants effectively use hydrogen bonding to the hexachloroplatinate anion by N–H moieties. Examining the conditions for the third phase formation revealed that the secondary amide extractant with the longest alkyl chain can be used in the extraction process for a long time without forming any third phase, despite its lower Pt(IV) extraction capacity. The practical trial with simple compounds developed in this study should contribute to the development of Pt separation and purification processes.

Effect of Initial pH and Organic Matter Concentration on Production of Volatile Organic Acids Through Acidogenesis of Sugarcane Vinasse

ABSTRACTSugarcane vinasse is an industrial liquid waste generated in great amounts in Brazilian ethanol industries. Nowadays its main use occurs at sugarcane crops, where vinasse is applied as a nutrient source for fertirrigation. However, continued use of vinasse in soil can cause several environmental impacts. So, aiming to provide a more environmentally friendly destination to the effluent, the goal of this work was to investigate the acidogenesis using a synthetic vinasse as substrate, focusing on the effects of initial pH and Chemical Oxygen Demand (COD) on short chain organic acids (SCOAs) concentrations. Synthetic vinasse was prepared at laboratory taking some real sugarcane vinasse composition given in previous works as references. So, major contribution presented here is the investigation on obtaining high added-value SCOAs from a simulated effluent. Cattle manure sludge was utilized as inoculum to promote the conversion of carbohydrate (sucrose, Suc) in synthetic vinasse into SCOAs in batch reactors during a total incubation time of 72 h. Acidogenesis profiles have shown that concentration of lactic acid (HLa) was prevailing among all metabolites, indicating that process followed through an essentially lactic route. Furthermore, considerable concentrations of propionic, acetic and isobutyric acids were also verified at some specific operation times, while solventogenesis was not detected at all. The greatest peak of lactate content was 4.96 g HLa L−1, observed under initial pH 6.0 and 25 g COD L−1, at 16 h. Maximum of lactate productivity was 332.10 g HLa L−1 h−1 at 8 h, associated to a yield of 189.14 g HLa (g Suc)−1, under initial pH 7.5 and 20 g COD L−1.

Removal of the pesticide methomyl contained in simulated effluent from equipment washing by adsorption in residual orange bagasse

This work consists of the study of methomyl removal, an extremely toxic carbamate pesticide, contained in aqueous solutions synthesized, by adsorption in residual orange bagasse from industrial juices processing. The adsorption kinetics was studied by obtaining the best fit for the model of pseudo-second order (R2= 0.949). The Langmuir isotherm model adjusted better to the experimental data confirming the adsorption in monolayers, without interaction among the adsorbate molecules. The scanning electron microscopy (SEM) revealed that particulate adsorbents have rather irregular surface, but with rigid structure and virtually no internal pores. The characterization of the functional groups by infrared spectroscopy (FTIR) revealed the presence of hydroxyl, Carbonyl and carboxylic groups on the adsorbents particles surface. Central composite rotational design 2x2 (DCCR 2x2) was used for the statistical study of the effects of pH and solid/liquid ratio (R) on the methomyl adsorption capacity in orange bagasse particles. The obtained mathematical model adjusted well to the experimental data (R2= 95%). In the studied intervals the highest values of adsorption capacity (q) were 3.73 and 3.43 (mg.g-1), obtained under the conditions of pH 6.0 with R 0.017 g.mL-1 and pH 4.5 with R 0.015 g.mL-1, respectively. Thus, it was possible to conclude that there was a greater adsorption in assays containing greater adsorbent mass in pH slightly acid.

The effect of clay tortuosity on contaminant plume persistence

<p>The presence of contaminated aquitards has been recognized as one of the main obstacles that hamper the successful aquifer restoration and the forward and back diffusion processes were known as the primary mechanism of solute exchange between the aquifer-aquitard system. In this study, a series of 2-D flow chamber experiments were conducted using 1 g/L of bromide solution as a non-reactive tracer to evaluate back diffusion phenomenon and plume tailing behavior based on different clay types (kaolinite, montmorillonite, and bentonite). In order to determine appropriate values for clay tortuosity, simulated effluent concentrations using 1-D analytical solutions were compared to the measured effluent concentrations. The best fits were found with for bentonite, for kaolinite, and The bentonite tortuosity value close to 1 indicates that the solute flowpath is similar to the aquitard straight-line distance under the saturated condition. Simulation results using the calculated tortuosity showed that bromide effluent concentration due to back diffusion from the montmorillonite layer decreased to 3 orders of magnitude below the initial concentration after 60 days of back diffusion. For bentonite, calculated effluent concentrations decreased to 3 orders of magnitude below the initial concentration after 230 days of back diffusion. These results suggest that the aquitard with higher tortuosity has more capability to sustain long-term plume persistence for non-reactive contaminants and more potential risks as secondary contaminant sources.</p>

Intensified Photocatalytic Degradation of Solophenyl Scarlet BNLE in Simulated Textile Effluents Using TiO2 Supported on Cellulosic Tissue

The Heterogeneous photocatalysis, increasingly used in effluent purification, is attracting more and more attention by the development of new photocatalytic materials based on semiconductors deposited on various supports. In this work, TiO2 supported on cellulosic fiber was prepared and characterized by different analytical techniques such as X-ray Photoelectron Spectrometry and Brunauer-Emmett-Teller surface area. Its photocatalytic activity was investigated for the degradation of Solophenyl Scarlet BNLE (SS), an organic pollutant present in textile effluents. Several conditions were investigated such as adsorption under UV and visible irradiation, catalyst recyclability, the simulated effluent pH and the presence of H2O2 as an oxidant agent. Results showed that under UV light, the removal of SS decreased significantly with increasing initial dye concentration. For an initial concentration of 5 mg/L, SS degradation was reached more than 95 % after 2 hours of treatment (neutral pH, T = 20 °C). The supported TiO2 on cellulose remains effective over four cycles of dye treatment. In the presence of H2O2, the degradation process was inhibited with increasing the molar ratio [H2O2]/[SS]0 from 5 to 30. The kinetic modeling showed that the removal of this pollutant followed a pseudo-first-order model (Langmuir-Hinshelwood) with a regression coefficient (R2) value of 0.984.

Catalytic Efficiency of Red Mud for the Degradation of Olive Mill Wastewater through Heterogeneous Fenton’s Process

Olive mill wastewater is a challenging effluent, especially due to its toxicity related to the presence of phenolic compounds. Fenton’s process was analysed on the abatement of phenolic acids typically found in this kind of effluents. To overcome the main drawback of Fenton’s process, a waste from the aluminium industry commonly called red mud was used as a heterogeneous source of iron. The adsorption of simulated effluent on the red mud was negligible. Therefore, the degradation of phenolic acids during Fenton’s process was due to oxidation by hydroxyl radicals. The amount of red mud and hydrogen peroxide were optimized regarding phenolic acids degradation. The optimal conditions leading to the highest removal of contaminants (100% of phenolic acids degradation and 25% of mineralization after 60 min of reaction) were 1 g/L of catalyst and 100 mg/L of hydrogen peroxide. The possibility of recovering treated water for agricultural purposes was evaluated by assessing the toxic impact over a wide range of species. The toxicity observed for the treated samples was mainly related to the residual hydrogen peroxide remaining after treatment.

pH: a promising indicator of feed waste in piggery effluent?

Feed waste in pork production sheds can amount to substantial economic losses. No simple methods exist to quantify this waste, which commonly ends up in the effluent stream. Monitoring piggery effluent might offer producers a practical alert solution for feed waste losses. We investigated piggery effluent pH as a potential marker of feed waste, given that most feed substrates and breakdown products are acidic whereas effluent is alkaline. To explore this prospective relationship, we constructed simulated effluent streams comprising faeces, urine and feed. These waste components were acquired from a commercial batch grower shed, at four different times over the 12-week growth cycle. In laboratory settings (25°C) we used the collected wastes to simulate the two stages of typical flushing piggery effluent systems: (1) Faeces + urine + feed waste accumulation in flushing channels, and (2) flush water mixing with these wastes in an effluent collection sump. We repeated the exercise for a one-off sampling event at a sow facility. For all events, at the grower and sow facility, the pH of the simulated effluents yielded exponentially decreasing relationships with increasing feed waste level (P < 0.05). For the grower facility we applied each of the four laboratory-derived relationships to the farm’s sump effluent pH, which was measured during each of these sampling events. The predicted feed waste levels were commensurate with estimates of feed waste for the same facility derived from alternative, time intensive approaches reported in other studies. Further work is needed to transition the promising results uncovered here into an alert system to help farmers improve profitability and minimise waste.