Graphene oxide (GO) based membranes show an advantage in desalination because of their unique water channels. Although influence of oxygenic groups of GO on water transport has become a focus of research, this is yet to be fully understood. In this work, the relative content of different oxygenic groups of GO was tuned by varying oxidation temperature (50, 60 and 70 °C). GO nanosheets were deposited on the permeate side of PVDF membrane in direct contact membrane distillation to enhance the desalination performance. The continuous GO layer enhanced flux by decreasing the vapor pressure at the permeate side. Salt rejection was improved from 99.2% of PVDF membrane to 99.9% of all the composite membranes. The deterioration of permeate quality caused by membrane wetting was avoided because the tiny solute in permeate was rejected by GO layer. Moreover, raising oxidation temperature resulted in GO that contains more epoxy groups, but less hydroxyl groups. GO oxidized at 70 °C provided the highest flux (17.80 kg m h) with enhancement proportion of 18.9% because it contains less hydroxyl groups but more epoxy groups. Therefore, the transformation of hydroxyl groups into epoxy groups of GO would be an effective approach for water flux enhancement of GO based membranes.

中文翻译：

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膜蒸馏中含氧基团对氧化石墨烯基膜脱盐性能改善的影响


氧化石墨烯（GO）基膜因其独特的水通道而在海水淡化方面显示出优势。尽管GO的含氧基团对水运输的影响已成为研究的焦点，但这一点尚未得到充分了解。在这项工作中，GO 的不同氧基团的相对含量通过改变氧化温度（50、60 和 70 °C）进行调节。在直接接触膜蒸馏中，GO 纳米片沉积在 PVDF 膜的渗透侧，以增强海水淡化性能。连续的 GO 层通过降低渗透侧的蒸气压来增强通量。脱盐率从PVDF膜的99.2%提高到所有复合膜的99.9%。由于渗透液中的微小溶质被GO层排斥，避免了因膜润湿而引起的渗透质量恶化。此外，提高氧化温度导致GO含有更多的环氧基团，但含有更少的羟基基团。 70°C 氧化的 GO 提供了最高的通量（17.80 kg mh），增强比例为 18.9%，因为它含有较少的羟基但较多的环氧基团。因此，将GO的羟基转化为环氧基团将是提高GO基膜水通量的有效方法。