Noval Technology For Food-Processing Wastewater Treatment Based On Molybdenum Sulfide Nanomaterials

In recent years,China's food industry has made considerable progress.Nevertheless,related environmental pollution has subsequently arisen.According to the report of the Ministry of Environmental Protection of the People's Republic of China,food industry has become one of the most important sources of industrial wastewater in China.However,traditional water treatment technologies have gradually failed to meet the needs of current society development.Thus,the development of cheap,convenient and efficient wastewater treatment technology has become a research hotspot.With excellent abilities to adsorb and degrade contaminants that are unmatched by conventional materials,nanomaterials bring a great opportunity for the innovation of wastewater treatment technology.Particularly,depending on their chemical form,molybdenum sulfide based nanomaterials have a variety of excellent properties,including hydrophobicity,low dimensionality,photothermal conversion capacity,catalytic activity,and adsorption capacity,which are suitable for contaminants removal from food-processing wastewater.Accordingly,considering the characteristics of main pollutants in food-processing wastewater,unique molybdenum sulfide based nanomaterials with excellent adsorption property and optical property were constructed,and applied to removal four main pollutants in food-processing wastewater through nano-adsorption or/and optical technology.The results of the study are as following:1.Preparation of novel oil adsorbent based on MoS₂/C foam?MoS₂/C?and its application for food-processing wastewater treatmentBy using a novel"nano-fixation"concept via a one-step pyrolysis method with ammonium tetrathiomolybdate and melamine foam as raw materials,a highly efficient oil adsorbent for food-processing wastewater treatment was prepared.The structure of the as-prepared foam adsorbent was then identified,and the adsorption ability and mechanism of foam adsorbent towards different organic solvents were also analyzed.The results demonstrated that MoS₂/C foam is mainly composed of MoS₂ nanoparticles and carbon foam with high porosity,low density and large specific surface area,as well as good hydrophobicity.As such,MoS₂/C foam can float on water and quickly sink into organic solvents,indicating its good hydrophobicity and lipophilicity.As such,MoS₂/C foam can absorb oil on water surface and under water with adsorption capacity of 65.3–159.5 times for common organic liquids,and can be used to rapidly remove oil from food-processing wastewater.2.Preparation of novel nano-microbicide based on chitosan functionalized magnetic MoS₂?CFM?and its application for food-processing wastewater treatmentA novel CFM decontaminating agent for microorganism removal in food-processing wastewater was prepared by simple ionic liquid-assisted milling,hydrothermal synthesis and stirring with molybdenum disulfide as substrate.By a variety of characterization techniques,the structure and composition of the material were identified.The effects of CFM on the separation and photothermal killing of microorganism were also evaluated to explore the mechanism and application prospect of microorganisms removal by CFM.The results showed that the content of chitosan in CFM was about 4.78 wt%and the saturation magnetization was6.6 emu/g.Through the electrostatic interaction between chitosan and bacteria,CFM can separate more than 90%bacteria from bacterial suspension within 0.5 min,demonstrating excellent cell separation performance of CFM.The results of further photothermal sterilization showed that the magnetic enrichment by CFM can significantly improve the photothermal killing effect of CFM towards bacteria.Additionally,CFM has good biocompatibility and can be used to efficiently remove and kill microorganism in food-processing wastewater.3.Preparation of new pigment degradation agent based on MoS₄^2-@ZIF-8?ZIF-MS?and its application for food-processing wastewater treatmentA one-step room temperature stirring method was applied to prepare MoS₄^2-@ZIF-8photocatalyst with photocatalytic activity for the degradation of pigments in wastewater of food industry.The synthesis conditions of ZIF-MS were optimized with photocatalytic activity as indicator,and 6 kinds of ZIF-MS?named as ZIF-MS-1,-2,-3,-4,-5 and-6,respectively?were obtained.The degradation ability,mechanism,and reusability of ZIF-MS photocatalyst towards illegally added dyes were then evaluated.The results indicate that ZIF-MS-6 and ZIF-MS-2 have the strongest photocatalytic activity,and can effectively degrade a variety of dyes through the generation of HO·radicals.Furthermore,ZIF-MS-2exhibits selective catalysis ability,and ZIF-MS-6 can degrade⁹5%lemon yellow or sunset yellow?10 ppm?within 1 h with good reusability.The practical application results showed that the photodegradation technology based on ZIF-MS towards organic contaminants can be effectively used in the removal of dyes from food-processing wastewater.4.Preparation of novel heavy metal adsorbent based on magnetic Mo-Fe-S cluster?FeMoS?and its application for food-processing wastewater treatmentWith ammonium tetrathiomolybdate and Fe₃O₄ nanomaterials as precursors,a magnetic Mo-Fe-S cluster-based nanosorbent capable of removing heavy metal ions from food-processing wastewater was prepared via simple mixing and stirring.By a variety of characterization techniques,the composition of magnetic composites was determined.The adsorption performance of FeMoS towards heavy metal ions was measured,and the reusability and adsorption mechanism were explored.The results show that tetrathiomolybdate ions can be fixated on Fe₃O₄ by the formation of Mo-Fe-S cluster.The prepared FeMoS can adsorb heavy metals through the formation of M-S bonds with heavy metals,exhibiting selective adsorption of heavy metal ions with a order of Zn²⁺,Mn²⁺,Ni²⁺<Cd²⁺?Cu²⁺<Pb²⁺.Thereinto,the pseudo-second-order kinetic model and Langmuir isotherm model demonstrated a fast adsorption activity of the Fe MoS NPs,and the maximum adsorption capacity for Pb²⁺is 319.35 mg/g,demonstrating that FeMoS has great potential to control heavy metal pollution in food-processing wastewater.5.New method for food-processing wastewater treatment based on the solar steam generation performance of MoS₂/C foamWith the ablity to absorb solar energy,MoS₂/C foam was further applied to purify food-processing wastewater via solar steam generating.Mo S₂/C foam-based oil adsorbent theoretically satisfies the requirement as an ideal solar absorber.IR imaging technology was conducted to analyze the solar-thermal conversion ability of MoS₂/C foam.Under simulated sunlight,the performance of MoS₂/C foam to generate steam by interfacial heating was then measured.The results show that MoS₂/C foam can effectively convert light energy into heat energy.As a solar adsorbent,it can float on water surface and interfacially heat water obtaining a water vapor generation efficiency of 1.458 kg/?m²·h?,with an energy conversion efficiency of 80.1%.The results of the application of wastewater purification show that MoS₂/C foam can be used to purify the food-processing wastewater through the occurrence of solar steam under natural sun light irradiation,providing a novel,green,and energy-saving technology for the treatment of industrial wastewater.