No abstract

Vapor−liquid equilibrium (VLE) data for aqueous systems in the presence of electrolytes have many industrial applications. VLE data for water + monoethylene glycol (MEG) mixtures in the presence of sodium chloride at low pressures are important to describe the effects of composition, temperature, and pressure on a MEG (gas hydrate inhibitor) regeneration unit. A modified version of the Othmer ebulliometer was applied to measure reliable VLE data for water + MEG + NaCl at 101.325, 65, and 35 kPa. Binary systems (water + MEG and MEG + NaCl) were also experimentally studied. Vapor pressures for water and MEG were determined and compared with the selected literature data via Antoine correlation. The electrolyte nonrandom twoliquid and universal quasi-chemical activity coefficient models were successfully parameterized to describe the VLE behavior for water + MEG + NaCl systems. Thermodynamic consistence of the data sets was also checked. Interaction parameter estimation followed a systematic strategy: (1) water−MEG, (2) water−NaCl, and finally (3) MEG−NaCl with the experimental data of MEG + NaCl and ternary data. MEG + NaCl solutions presented an inverted colligative property, that is, the addition of salt decreases the boiling point. VLE data indicated that water separation is less efficient due to the addition of salt. The parameterized models allow an evaluation of the MEG regeneration process as a function of temperature, pressure, and composition.

Purpose Bacterial cellulose (BC), obtained by fermentation, is an innovative and promising material with a broad spectrum of potential applications. Despite the increasing efforts towards its industrialization, a deeper understanding of the environmental impact related to the BC production process is still required. This work aimed at quantifying the environmental, health, and resource depletion impacts related to a production of BC. Methods An attributional life cycle assessment (LCA) was applied to a process design of production of BC, by static culture, following a cradle-to-gate approach. The LCA was modeled with GaBi Pro Software using the ReCiPe 2016 (H) methodology with environmental impact indicators at midpoint level. The functional unit was defined as 1 kg of BC (dry mass), in 138.8 kg of water. Results From the total used resources (38.9 ton/kg of BC), water is the main one (36.1 ton/kg of BC), most of which (98%) is returned to fresh waters after treatment. The production of raw materials consumed 17.8 ton of water/kg of BC, 13.8 ton/ kg of BC of which was for the production of carton packaging, culture medium raw materials, and sodium hydroxide (for the washing of BC). The remaining consumed water was mainly for the fermentation (3.9 ton/kg) and downstream process (7.7 ton/kg). From the identified potential environmental impacts, the production of raw materials had the highest impact, mainly on "Climate change", "Fossil depletion", "Human toxicity, non-cancer", and "Terrestrial toxicity". The sodium dihydrogen phosphate production, used in the culture medium, showed the highest environmental impacts in "Human toxicity, non-cancer" and "Terrestrial ecotoxicity", followed by corn syrup and carton production. The static culture fermentation and downstream process showed impact in "Climate change" and "Fossil depletion". Conclusions Per se, the BC production process had a small contribution to the consumption of resources and environmental impact of the BC global life cycle.

Monoethylene glycol (MEG) is used to prevent hydrate formation in subsea pipelines of natural gas production. MEG is recovered at an offshore regeneration unit. Sodium chloride is the predominant salt in the water−MEG streams. Thus, knowledge of NaCl solubilities in the process conditions is relevant for the design and operation of a MEG regeneration unit. Six isotherms of NaCl solubility were measured (76 data points) from T = (293.15 to 403.15) K in the whole solvent concentration range. The analytical method for salt solubility was based on the reproducibility of the concentration of two successive samples. Density measurements were accurately applied for these analyses. The temperature dependence on NaCl solubility is relatively weak. A reverse behavior with increasing temperature was observed for MEG contents higher than 90 wt %. Salt solubilities were successfully correlated with Redlich−Kister expansion (AADw NaCl = 0.0006 and Δw NaCl = 0.47%). Electrical conductivity of NaClsaturated solutions were measured (44 data points) at T = (293.15 to 363.15) K and correlated with a semiempirical model. A large difference in electrical conductivity for the two solvents was observed. The correlation adequately represented the data set (AADκ = 5.67 mS•cm −1 and Δκ = 5.94%). NaCl solubilities and electrical conductivities were accurately determined and are useful for the MEG regeneration process.

An artificial neural network (ANN) was implemented for modeling phenol mineralization in aqueous solution using the photo-Fenton process. The experiments were conducted in a photochemical multi-lamp reactor equipped with twelve fluorescent black light lamps (40 W each) irradiating UV light. A three-layer neural network was optimized in order to model the behavior of the process. The concentrations of ferrous ions and hydrogen peroxide, and the reaction time were introduced as inputs of the network and the efficiency of phenol mineralization was expressed in terms of dissolved organic carbon (DOC) as an output. Both concentrations of Fe(2+) and H2O2 were shown to be significant parameters on the phenol mineralization process. The ANN model provided the best result through the application of six neurons in the hidden layer, resulting in a high determination coefficient. The ANN model was shown to be efficient in the simulation of phenol mineralization through the photo-Fenton process using a multi-lamp reactor.