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The phase diagrams and compositions of coexisting phases have been determined and correlated for poly­(ethylene glycol) (PEG) 3000 + trisodium citrate aqueous two-phase systems (ATPS’s) at 25 °C and different pH values (6.1, 7.5, and 9.0). It was found that an increase in pH caused the binodal curve to be displaced downward and also the expansion of the two-phase region. The experimental binodal data of the mentioned system has been successfully correlated with Bleasdale equations (high R 2 and low AARD). Furthermore, the viscosities, densities, electrical conductivity, and refractive index of binary (PEG 3000 + water; trisodium citrate + water) and ternary (PEG 3000 + trisodium citrate + water) systems at the above pH value have been measured and correlated. The density data show a linear variation with mass fraction of the polymer and also the salt. The viscosity data of PEG 3000 solutions were correlated as a function of mass fraction, using a nonlinear equation. The effect of tie line lengths on density and viscosity of the aqueous two-phase systems has also been represented.

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The present work reports the liquid–liquid equilibrium (LLE) measurements and the construction of binodal curves for polyethylene glycols (PEG) + zinc sulfate/ammonium sulfate + water at three different temperatures (298.15, 303.15, and 308.15 K) and pH values (3.00, 4.70, and 5.21). PEGs with different molecular weights of 2000 g·mol–1 (PEG 2000), 3000 g·mol–1 (PEG 3000), and 8000 g·mol–1 (PEG 8000) were chosen for this study. The phase composition was obtained by measuring the refractive index (n D) and density (ρ) and was further used to obtain the tie-line length (TLL) and the slope of tie-line (STL). The tie-lines are reported at different polymer lengths, pH values, and temperatures. The values of the effective excluded volume (EEV) were employed to analyze the effect of the parameters on the binodal curves. Moreover, the impact of those parameters on the TLL and STL and plait point are discussed and compared with the results of the literature. Furthermore, the binodal curves data and the tie-lines’ ends were fitted using some semiempirical equations with satisfactory results. Finally, the UNIFAC is used to calculate the LLE data of the above system and the adjusted binary group interaction parameters of the model were reported.

Industrial agriculture is not efficient anymore due in particular to the use of nonrenewable energy such as fossil fuels. Organic agriculture is an alternative system that aims to reduce the consumption of fossil fuels, pesticides, and mineral fertilizers. Animal-crop systems present potential mutual benefits, but such systems have been rarely studied quantitatively. Here, we compare energy inputs and outputs of organic riceduck farming with conventional rice production in Mazandaran province, Iran. Our results show that the global energy input of organic rice-duck, 79,307 MJ ha . The most used energy was fuel, amounting to 40 % of total energy for organic rice-duck and 33 % for conventional rice. Then, machinery consumed 25 % of total energy for organic rice-duck and 20 % for conventional rice. Then, fertilizers consumed 20 % of total energy in the form of organic fertilizers for organic rice-duck versus 16 % in the form of mineral fertilizers for conventional rice. Overall, our findings show that organic rice-duck farming has more energy efficiency than conventional rice farming.

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