No abstract

Photoelectrocatalysis is a novel technique that combines heterogeneous photocatalysis with the application of an electric field to the system through electrodes for the degradation of organic contaminants in aqueous systems, mainly of toxic dyes. The efficiency of these combined processes depends on the semiconductor properties of the catalysts, as well as on the anodic capacity of the electrode. In this study, we propose the use of active hydrotalcites in the degradation of Congo red dye through processes assisted by ultraviolet (UV) irradiation and electric current. Our research focused on evaluating the degradation capacity of Congo red by means of photolysis, catalysis, photocatalysis, electrocatalysis, and photoelectrocatalysis, as well as identifying the effect of the properties of the active hydrotalcites in these processes. The results show that a maximum degradation was reached with the photoelectrocatalysis process with active hydrotalcites and a copper anode at 6 h with 95% in a half-life of 0.36 h. The degradation is favored by the attack of the OH• radicals under double bonds in the diazo groups where the electrode produces Cu2+ ions, and with the photogenerated electrons, the recombination speed of the electron–hole in the hydrotalcite catalyst is reduced until the complete degradation.

Textile manufacturing is the one responsible for water bodies' contamination through the discharge of colored wastes. This work presents the study of reactive yellow HF (RYHF) dye degradation under two different electrochemical advanced oxidation processes (EAOP), namely anodic oxidation (AO) and electro-Fenton (EF)/boron-doped diamond (BDD) process. For the AO, 100 and 300 mg/L solutions using Pt and BDD as anodes in a 100 mL stirred tank cell were used, with a supporting electrolyte of 0.05 mol/L of NaSO at pH 3 under 30 and 50 mA/cm current density. The EF/BDD process was carried out in a flow reactor at 4 and 7 L/min to degrade 100, 200, and 300 mg/L RYHF solutions under 50 and 80 mA/cm. UV-Vis determinations were used for decolorization evaluation, while high-performance liquid chromatography (HPLC) method provided information on dye degradation rate.

The wood chemical composition was determined for five tree species that cohabitate in the forest of Ixtlán de Juárez (Oaxaca, Mexico). These species were Alnus acuminata, Arbutus xalapensis, Myrsine juergensenii, Persea longipes, and Prunus serotina. The chemical composition was then correlated with the higher heating value of the wood. The chemical components determined were total extractives, ash, lignin, and holocellulose (alpha cellulose and hemicelluloses). The extractives were separated using Soxhlet equipment, and the ash obtained was analyzed via atomic absorption spectrometry. On average, the species presented 8.26 to 19.64% of total extractives, 0.56 to 1.50% of ash, 23.1 to 37.2% of lignin, 74.0 to 79.5% of holocellulose, 56.3 to 66.3% of α-cellulose, and 12.3 to 21.0% of hemicelluloses. In the ash, higher percentages of calcium, potassium, and magnesium were detected. The amount of chemical components was different between species (p ≤ 0.05). The higher heating value showed a positive correlation with the extractives content (r = 0.582), while with the ash content it was negative (-0.575). The high proportions of polysaccharides predict good performance of these species in pulp production, and the calorific value indicates that they have the potential for use as fuel.

The estimation of tree biomass serves as a parameter of forest productivity; in addition, it is a method to estimate carbon fixation and storage. Studies on total biomass that include the belowground component for the Pinus genus are scarce in Mexico due to the difficulty and high costs for its quantification. In this study, allometric models were fitted to estimate the total biomass of Pinus patula Schiede ex Schltdl. & Cham., from the pine-oak forest of Ixtl an de Ju arez, Oaxaca, for which a destructive analysis was made of 25 trees distributed in five diameter classes, classifying the biomass by components (root, stem, branches and foliage). With the component biomass data, different models were fitted by nonlinear regression techniques, using the diameter at breast height (D, cm) and the total height (TH, m) as independent variables. The model with the best fit was an exponential type y ¼ e ðÀb 0 þb 1 ln ðDÂTHÞÞ : In this study, it was observed that the studied species stores 22.62% of the biomass in the root, 69.61% in the stem, 5.67% in the branches and 2.11%, in the foliage. The models proposed in this study allow the estimation of total biomass and by structural component independently and additively. Its use is recommended in trees of P. patula, in the range of 5 to 25 cm of diameter at breast height, in forests with similar growing conditions.