Study On Comprehensive Utilization Of High-salinity Wastewater Resources

High-salinity wastewater is defined by its overall mass fraction of salts(no less than 1%).It derives from a wealth of sources and has complicated compositions.It often contains not only large amounts of inorganic salts but also organics and heavy metal ions.Therefore,its direct emission will lead to waste of salt and water resources and contamination of environment.It is of great significance to recover the inorganic salts and water resources considering resource shortage and environment pollution issues.The efficient removal of the organics and heavy metal ions in high-salinity wastewater and furthermore the recovery of inorganic salts as well as the utilization of water have been among the hottest and most difficult subjects in this field.Aiming at the utilization of high-salinity wastewater,this study is focused on the recovery and utilization of inorganic salts and water resources.To begin with,novel magnetic montmorillonite/Fe₃O₄/humic acid nanocomposites(of physical removal mechanism)were synthesized to eliminate the effects of organics and heavy metal ions on resource recovery.The effects of various operation conditions on the removal performance,the adsorption mechanisms towards different contaminants,and the reusability of the two nanocomposites were studied.Then,to further improve the performance of nanocomposites,novel magnetic Mo S₂/Fe₃O₄/n ZVI nanocomposites(of physical-chemical removal mechanism)were synthesized and studied to compare the properties in contaminant removal.After removal of organics and heavy metal ions,the pseudo-ternary phase diagrams were plotted based on the measurement of the solid-liquid phase equilibrium data of NaCl-Na₂SO₄-water pseudo-ternary system in the temperature range of 268.15-373.15K.The crystallization methods of NaCl and Na₂SO₄ were determined on the basis of their actual mass fractions in high-salinity wastewater and a fractioanl crystallization route was established to recover the NaCl and Na₂SO₄ resources.In this way,NaCl and Na₂SO₄ of high purities and industrial values were successfully recycled by crystallization methods.Last but not least,large amount of water,which can be utilized in photocatalytic water oxidation,was recycled from the evaporation operation during the crystallization of inorganic salts.A new series of transition metal doped polyoxovanadates containing bismuth were first prepared through a simple route using commercially available starting materials,and then were utilized as single source precursors to develop a novel synthetic method which can be used to fabricate BiVO₄ photoanodes with different transition metals as dopants.The effects of various dopant transition metals on photocatalytic activities were also compared.Finally,cobalt-doped BiVO₄ photoanodes of larger sizes were fabricated via the same route to realize the industrialization of solar water oxidation.