Commercial nanofiltration (NF) membranes have been used to separate dyes and salts in industry; however, NF membrane’s high rejection to divalent salts (i.e., Na2SO4) leads to a reduction of salt recovery. In this study, a tight ultrafiltration (t-UF) ceramic membrane (MWCO 8800 Da) is proposed to fractionate dyes and mixed salts (NaCl/Na2SO4) for textile wastewater treatment. Performance of the t-UF ceramic membrane and DK polymeric membrane (from GE) has been compared regarding to permeability, retention of reactive dyes, and permeation of salts. The t-UF ceramic membrane presents better permeability, competitive rejection of dye molecules (>98%), and reduced rejection of NaCl (<10%) and Na2SO4 (<30%) in comparison with DK membrane; the pure water permeability of t-UF membrane is at least 6 times that of DK membrane. In particular, the operation parameters (TMP, temperature, and pH) and solution environment (concentration and charges) have been intensively evaluated for dye/dual-salts separation efficiency in the membrane process. It also reveals that the t-UF ceramic membrane has performed negative rejection to chloride ions at low operating pressure in the dye and NaCl/Na2SO4 solution due to the electrostatic Donnan effect. Concentration of salt, valence of inorganic ions, and charge of dyes are found as having a significant effect on membrane separation performance. In conclusion, the strong retention of dyes and free permeation of salts (i.e., low retention) by the t-UF ceramic membrane proves that it can be applied to desalinate dyeing wastewater of high salinity and recover dyes and salts separately.

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Litter is an important component of forest ecosystems and plays an important eco-hydrological function. Many studies have been carried out on litter at present, but less research has been carried out on the eco-hydrological service functions of litter in different plant communities in Karst, especially in the area of Karst peak-cluster depressions in southwest China. To reveal the characteristics of the hydrological function of the litter layer of the plant community in the area of Karst peak-cluster depressions around FAST (Five-hundred-meter Aperture Spherical Radio Telescope), three typical plant community litter layers of the broad-leaved forest, coniferous forest, and shrub were selected as research objects, and the hydrological function of the litter layer of different plant community types was studied using the immersion method. The results indicated: 1) The litter layer of the broad-leaved forest plant community has the strongest function of intercepting and regulating precipitation (Mlmax = 24.17±0.33 t/ha, Msv = 19.93±0.21 t/ha), and its hydrological service function is the best. 2) The higher the decomposition degree of litter, the stronger the interception function. 3) The fitted equations for both the litter water-absorption capacity (Qct) and time (t) for plant communities were Qct = b + alnt, and the fitted equations for both the litter water-release capacity (Qst) and time (t) were Qst = a t b. 4) The fitted equations for both the water absorption and release rates (vc and vs) and time (t) of the litter were v = a t -b. The water absorption rates of litter were the fastest within 5 min (15529.01~22634.43 g/kg·h), with the greatest interception and storage function for short-term rainfall.

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