Dongyi Yang,Cheng Chen,Jiqing Xie,Yuanqing Ye,Zhi Zhou,Huiyun Liao,Zhong Yao
The application of pervaporation technology in the recovery of aromatic compounds from water faces the challenge of low performance. In this paper, a uniform zeolitic imidazolate framework/polydimethyl-siloxane (ZIF-8/PDMS) composite membrane was fabricated by means of contra-diffusion crystallization and a casting method in sequence. The diffusion time was optimized to be 24 h. ZIF-8/PDMS showed improving performance to pure PDMS . The permeation flux of linalool, neral, and geranial in ZIF-8/PDMS increased by 73.3%, 110.9%, and 106.0%, respectively; and the separation factors were also improved. The separation effect of neral (cis-citral) was much better than that of geranial (trans-citral), suggesting the potential enantioselectivity. In ternary model system, the separation of citral (neral and geranial) was competitively restrained by the presence of linalool. ZIF-8/PDMS also showed good performance in real lemon oil. After treatment for 9 h, the recovery rates of linalool, neral and geranial were 97.20%, 96.15%, and 92.56%, respectively.
Manquan Fang,Chilung Wu,Zhengjin Yang,Tao Wang,Yang Xia,Jiding Li
In this contribution, zeolitic imidazolate framework (ZIF-8)/polydimethylsiloxane (PDMS) mixed matrix membranes (MMMs) were prepared for hydrocarbon recovery using propane/nitrogen mixture as a model feed gas pair. All MMMs obtained a homogeneous particle dispersion and intimate interface interaction, which were confirmed by high resolution scanning electric microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) mapping. Gas permeation test shows that ZIF-8/PDMS MMMs demonstrate an enhanced separation performance with improved separation selectivity (38% higher than that of pure PDMS membranes) and propane permeance over 100 GPU. However, it is worth noting that the enhanced selectivity and decreased permeance of MMMs contradict the prediction by Maxwell model, which suggests the existence of pore blockage and inhibited chain mobility at polymer-particle interface. The inhibited chain mobility is further confirmed by differential scanning calorimetry (DSC) analysis. Based on these observations, a new modified Maxwell model is proposed taking non-ideal interface morphology and particle agglomeration into consideration. Both the selectivity and gas permeance predicted by the proposed model are in good agreement with experimental data, which thereby extends the application scope of original Maxwell model.
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