Polysulfone (PSU) film and N-vinylimidazole (VIM) were used to obtain grafted membranes with high hydrophilic capacity. The grafting process was performed by gamma irradiation under two experiments: (1) different irradiation doses (100–400 kGy) and VIM 50% solution; (2) different concentration of grafted VIM (30–70%) and 300 kGy of irradiation dose. Characteristics of the grafted membranes were determined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), contact angle, swelling degree, desalination test, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Both experiments indicated that the absorbed dose 300 kGy and the VIM concentration, at 50% v/v, were effective to obtain PSU grafted membranes with 14.3% of grafting yield. Nevertheless, experimental conditions, 400 kGy, VIM 50% and 300 kGy, VIM 60–70% promoted possible membrane degradation and VIM homopolymerization on the membrane surface, which was observed by SEM images; meanwhile, 100–200 kGy and VIM 30–50% produced minimal grafting (2 ± 0.5%). Hydrophilic surface of the grafted PSU membranes by 300 kGy and VIM 50% v/v were corroborated by the water contact angle, swelling degree and desalination test, showing a decrease from 90.7° ± 0.3 (PSU film) to 64.3° ± 0.5; an increment of swelling degree of 25 ± 1%, and a rejection-permeation capacity of 75 ± 2%. In addition, the thermal behavior of grafted PSU membranes registered an increment in the degradation of 20%, due to the presence of VIM. However, the normal temperature of the membrane operation did not affect this result; meanwhile, the glass transition temperature (Tg) of the grafted PSU membrane was found at 185.4 ± 0.5 °C, which indicated an increment of 15 ± 1%.

In this study, pectin extraction from fruits peel of Opuntia robusta was investigated. Pectin was extracted by microwave and conventional heating methods, and the product was analysed to determine the yield, esterification degree, galacturonic acid content, molar mass, antioxidant, emulsifying and rheological properties. The extraction methods resulted in two different types of pectin: pectin I, with high (> 50 %) methoxyl degree of esterification, and pectin II, with low, (< 50 %) methoxyl degree of esterification. The extraction yield of these pectins was 14.64 and 15.71 %, with molar masses of 33,110 and 20,339 g mol À 1 , respectively. Pectin II showed the highest galacturonic acid content (47.05 %) in comparison with pectin I (31.74 %). The antioxidant properties of pectins showed similar polyphenols content. However, pectin II had the highest scavenging activity. Finally, pectin I displayed the best emulsifying properties, and both pectins produced shear-thinning solutions and predominantly elastic gel behaviour.

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