Use Of Self-floating Adsorbents/Catalyst For The Treatments Of Dyeing Wastewaters And As(Ⅲ) Wastewater

At present,sedimentation and filtration are the most commonly used methods for solid-liquid separation of water treatment materials.However,the efficiencies of sedimentations are low due to most of the substances（E.g.activated sludge,coagulants,activated carbon）used in water treatments own poor sedimentation performances.For filtration,the uses of the filter materials and the additional energy consumption required by the backwashing process will also increase the cost of the water treatment processes.To achieve more efficient and economical solid-liquid separation efficiency,novel solid-liquid separation technology is needed to research and develop.In this study,the concept of water treatment agent self-floating was proposed for the first time.After using hollow glass microspheres（HGM）to be the carriers of water treatment agents,and modifying HGM’s surface in different ways,adsorbents and catalyst with self-floating ability were prepared and used for the adsorptions of dyes and oxidation of arsenic（Ⅲ）（As（Ⅲ））.The prepared self-floating water treatment materials are stable and lightweight,which can float up in water via buoyancy force and enrich on the water surface,to realize the solid-liquid separation between water treatment agents and water at the surface.At the same time,the separation system is also beneficial to the subsequent regenerations and reuse processes of water treatment agents.The specific research contents and conclusions are as follows:1)A 2-acrylamide-2-methylpropane sulfonic acid（AMPS）grafted self-floating adsorbent（AFA）was successfully prepared by grafting AMPS onto the HGM surface.The prepared AFA surface carries a large number of negative charges,and the adsorptions of cationic dyes were realized via the strong electrostatic attractions between charges.Besides,AFA’s unique shell structure gives it a stable self-floating ability,which makes adsorbents easier to be enriched and separated at the water surface.AFA and its intermediates were characterized by SEM,EDS,XPS,FT-IR,BET,TGA,and XRD,and the results showed that the AMPS was grafted successfully.The adsorption experiments showed that the adsorption capacities of AFA for cationic dyes including methylene blue（MB）,malachite green（MG）,basic fuchsin（BF）,and crystal violet（CV）at the optimal condition were 436.8 mg/g,637.6 mg/g,457.8 mg/g,and399.4 mg/g,respectively.2)The polymeric organic compound,poly-dopamine（PDA）can be used to prepare multi-functional adsorbents due to its abundant amino groups and aromatic rings.A self-floating shell structured adsorbent,EPDA-SA,was prepared by co-grafting PDA and methylacryloxyethyl trimethylammonium chloride（DMC）on the HGM surface.SEM,EDS,BET,XPS,FT-IR,TGA,and XRD were used to characterize the surfaces of the synthesized microspheres.The physical and chemical properties and the synthesis pathways of the adsorbents were also identified.EPDA-SA can adsorb acid green 25（AG25）quickly and efficiently through charge attractions andπ-πstacking interactions.The removal efficiency of 0.1m M AG25 can reach 94.51%within 60 min.The results of the adsorption isotherm and kinetic studies showed that the adsorption process had a higher R²to the Langmuir isotherm model and PSO kinetic model.Besides,the synthesized adsorbent has good reusability and maintained ideal adsorption performance after 5 recycles.3)M-phenylenediamine（MPD）,the raw material for organic synthesizes,has good co-presence with anionic organic sodium allyl sulfonate（ALS）,which can be co-grafted on the surface of HGM to prepare a multi-functionalized amphoteric self-floating adsorbent,HGM@MPD-ALS.The results of multiple characterizations showed that the corrosion of sodium hydroxide significantly improved the surface roughness and the number of–Si–OH groups of HGM in the pretreatment process.The functional groups such as aromatic rings,–NH₂,and–HSO₃^-were grafted onto the surface of HGM after the synthesis process.The synthesized amphoteric adsorbent has amphoteric adsorption capacities for the anionic dye acid green 25（AG25）and the cationic dye basic fuchsin（BF）.Kinetic and isotherm studies showed that the PSO model and Langmuir model had the highest fitting degree for the adsorption processes.The theoretical maximum adsorption capacities of HGM@MPD-ALS for AG25 and BF reached 454.55 mg/g and588.24 mg/g,respectively.The mechanism studies showed that charges attractions,π-πstaking,and hydrogen bond were the potential interaction forces between dyes and adsorbents.Due to the hollow structure of HGM and the slight interaction of agglomeration,the surface enrichment rate of HGM@MPD-ALS was over 95.7%via the self-floating process within 12 min,which was conducive to the subsequent solid-liquid separation process and the reuse of adsorbents.4)A self-floating copper loaded catalyst HGM-N-Cu with hollow structure was prepared by using copper ammonia complex and HGM as a copper source and base-material,respectively.The results of SEM,TEM,BET,XPS,and XRD showed that the catalyst owned ideal specific surface area and stability,and the active catalytic sites of copper were uniformly distributed on the surface of the microspheres.The prepared HGM-N-Cu in sulfite（S（IV））system had been successfully applied to the oxidation of arsenic（Ⅲ）（As（Ⅲ））in a near-neutral condition.The effective activation of S（IV）by HGM-N-Cu involves the Cu（II）/Cu（I）transformation and the chain reaction of sulfur oxides,in which S（IV）can be used as the ligand of the Cu（II）at the surface and the precursor of sulfur oxides.The apparent reaction rate constant(k_obs’)of the formation of SO₄^·-in the system was calculated as 1.81±0.12 M^-1 s^-1,and the reaction rate constant(k₁₂)for SO₅^·-+As（Ⅲ）→As（IV）+SO₅^2-was calculated as 2.6×10⁶ M^-1 s^-1by kinetic study for the first time.Besides,the reaction system had low apparent activation energy（Ea）,which was calculated as 48.6±0.1 k J mol^-1.The self-floating process can effectively separate the catalyst.The catalyst maintained good stability and reusability after six recycles.Moreover,the catalytic oxidation system could realize the effective oxidation of As（Ⅲ）in a wide range of geochemical conditions.