Mixed matrix membranes combining the processibility of polymers with the properties of porous nano-additives is an effective method to enhance the performance of membrane distillation (MD) process. In this work, a new type of hydrophobic hybrid PVDF hollow fiber membranes doped with aluminum fumarate metal-organic frameworks (AlFu MOF) was fabricated and their performance in direct contact membrane distillation were studied experimentally and theoretically.The results showed that the addition of MOF particles efficiently enlarged the effective porosity of membrane and increased the water flux as well as the thermal efficiency of MD process. At 1 wt% MOF loading, the effective porosity of membrane was enlarged by 52.4%, which induced 55.9% increment in overall mass transfer coefficient of the hybrid membrane, and the thermal conductivity of the membrane was decreased by 38.6%, which contributed to the reduction of sensible heat loss of MD. Correspondingly, the experimental water flux of the hybrid 1 wt% MOF/PVDF membrane was improved by 50.5% and the thermal efficiency increased by 46.2% (0.58 vs 0.31) at a feed temperature of 40°C. Moreover, the MOF/PVDF membrane exhibited stable flux and retained high salt rejection (> 99.9%) for 3.5 wt% NaCl solution over a 50 h desalination test period. Overall, this 15 study provides an insight into the positive effects of AlFu MOF additives on the enhancement of 16 membrane performance in distillation process.

No abstract

The Corn Belt of Northeast China is the most important corn production area in China, accounting for 30% of the total corn production. However, seasonal drought conditions limit local corn production. Field experiments were conducted in 2011 and 2012 in Lishu county (Jilin Province, China) to study the effects of ridge and furrow rainfall harvesting and mulching on corn yields, evapotranspiration (ET), and water use efficiency (WUE) in black and aeolian sandy soils. The treatments included flat planting bed (FB), plastic-mulched ridges with bare furrows (RFB), and plastic-mulched ridges with straw-mulched furrows (RFM). For both soil types, the RFB and RFM treatments improved soil water conditions in the root zone. However, adding straw mulch did not consistently improve soil water content. In the black soil, the RFB treatment did not affect crop yield but increased WUE by 13% relative to the FB treatment in 2011. Furthermore, yield and WUE decreased by 30 and 24%, respectively, in 2012. In the aeolian sandy soil, the RFB treatment increased yield and WUE by 26 and 25%, respectively, relative to the FB treatment in 2011. However, the RFB treatment had no effect on yield or WUE in 2012. For both soil types, the RFM treatment did not significantly affect yield or WUE relative to the RFB treatment during 2011 or 2012. Therefore, the RFB treatment should only be used in aeolian sandy soils to achieve higher corn yields and WUEs and not be recommended for black soils when the soil water is sufficient.

This study investigated the performance and applicability of a composite dual-layer PTFE membrane coated with a dense hydrophilic polyurethane layer for treating wastewater containing surfactant and solvent in direct contact membrane distillation process. The influences of operating temperature and water recovery on bare and composite PTFE membranes were studied using simulated wastewaters containing sodium chloride together with sodium dodecyl sulfate or ethanol. In contrast to the significant wetting of bare PTFE membrane due to the adsorption of wetting agent on membrane surface, the composite membrane exhibited satisfied anti-wettability and desalination stability. The mechanism of anti-wettability of the composite membrane was related to the repellent effect of hydrophobic moiety of surfactant arrayed on the hydrophilic layer of the composite membrane, which prevented the wetting agent from reaching the hydrophobic layer of membrane. The results indicate that the dual-layer membrane could be potentially used to tackle organic solvent and/or surfactant containing wastewaters.