Superficial Modification Of Porous Ceramics Filter Media On The Basis Of Red Mud And Its Application In The Water Treatment

Red mud is the largest number of industrial hazardous waste in nonferrous metals industry of China and its output is more than 10 million ton every year.Red mud loss and lye leakage have brought severe pollution to farmland,river and groundwater.At present,effective ways of extensive utilization to red mud are not found and comprehensive utilization of red mud has become the bottleneck limiting the fast development of aluminum industry in China.Most oilfields adopt water reinjection process from oil field produced water to drive oil from strata in China. Pollutants in oil field produced water,such as oil,iron,suspend substance, microorganism,and so on,will lead to formation plugging,pipeline jam and corrosion and production cost rising.Effluent quality treated by available process can not meet with the Al quality standards of recommended indexes in SY/T5329-94 about the injection water quality for clastic rock oil fields in China.A huge quantity of dye wastewater is discharged by textile,paper,plastic and leather industries every year.As many dyes are complex organic contained azo and poly aromatic ring,which may cause people abnormal,cancerous and mutagenic,the removal of dyes from these wastewaters is a very important subject.Lots of dyes are resistant to oxidation and degradation,so adopting adsorbent to remove the dyes may be superior to other methods.The activated carbon is a very effective adsorbent, but its high price limits its extensive use.So,it is vital that lost-cost adsorbent should be prepared.However,researches on treatment of oil field produced water and dyes wasterwater by red mud are fewer and the studies on process and theory on treatment of oil field produced water and dyes wastewater by porous ceramics filter media based red mud are still expected to be carried out further.In this paper,safe disposal of red mud will be combined with treatment of oil field produced water and dyes waster water in order to implement the target based on waste control by waste.According to filter material gradation demand in the filtration process,regulation study on volume density,apparent porosity and the balance of apparent porosity with crushing strength is going to be evolved. Superficial modification to porous ceramics filter materials based on red mud was first put forward with hydrogen-containing silicone oil,benzeneless ecological paint and ferric nitrate and related properties were characterized by test measures such as FTIR,SEM and XRD.Based on these,coagulation-coalescence filtration coupling process for oil field produced water and adsorption process for methylene blue were brought forward.At the same time,a series of researches on influencing factors about treatment effect,optimization of process operation parameters,pollutant removal mechanism and regeneration of modified filter material were made.The main achievements are as follows:(1)Effect of pore-forming agent kinds,pore-forming agent addition,graded aggregate,graded pore-forming agent,firing temperature on apparent porosity, volume density and crush strength of filter material was studied.Coal was chosen as optimal pore-forming agent and the relation between coal addition with apparent porosity and volume density of filter material was linear.So,regulation to apparent porosity and volume density of filter media could be come true by coal addition.The relation between apparent porosity and crush strength of filter material accorded with quadratic curve.Thus,contradiction between apparent porosity and crush strength of filter material was conciliated by control to coal addition combining imitative straight line equation about coal addition and apparent porosity,which could make apparent porosity and crush strength a higher value.(2)Superficial modification to porous ceramics filter materials based on red mud was first put forward with hydrogen-containing silicone oil,benzeneless ecological paint and ferric nitrate.After oleophylic and oleophobic modification, contact angles for water of patch test matrixes were from 25°to 138°and 6°, suggesting that oleophylic and oleophobic performance of filter material increased, which lead to the capacity increase of wet and collision coalescence of filter material. At last,oil removal rate in the oil field produced water rose by use of modified filter material.After modification with iron oxide compound,special surface area and iron overlay quantity of filter material were 4.987m~2/g,12.9016mg/g,respectively and its total pore volume increased from 0.005049cm~3/g to 0.01417cm~3/g.So,the adsorption capability of filter material was improved.(3)The design was discussed on newly integrated and high efficiency oil removal equipment and coagulation-coalescence filtration coupling processes for oil field produced water were brought forward.Coagulation process parameters were optimized by parallel 6 beakers mixer.Design and operation parameters of newly integrated equipment were also optimized by small experiment,pilot test and productive field experiment.The results were that treatment efficiency was better integrated equipment than walnut shell filter of oil production team 22 of Jianhan Oilfield in China and effluent quality met with the Al quality standards(Oil content, SS,total iron content were less than 5mg/L,1mg/L,and 0.5mg/L,respectively). Mechanisms of oil removal included coagulation(which lead to demulsification of emulsified oil,and demulsifying oil was suspension or settlement),wetting adsorption coalescence of oleophylic filter material(when coalescing oil on filtration media arrived at some size and thickness,it would fall off from filtration media surface at water flow impact,at the same time,desquamated oil was intercepted between filtration media),collision coalescence of oleophobic filter material(Small size oil drop assembled to big size oil drop,which lead to oil floating upward or intercepted between filtration media)and synergistic effect of SS(Oil drop adhering to SS were intercepted between filtration media).SS removal mechanisms consisted of resistance interception,gravity sedimentation and contact flocculation.Major removal mechanisms of iron included settlement,interception based on filtration and adsorption.(4)Effect of factors on adsorption removal of MB from aqueous solution using iron-oxide coated porous ceramics filter media(IOCPCFM)was investigated in batch mode and column mode.In batch mode,at pH=11,negative charge in IOCPCFM surface was favor of adsorption of MB which was positive ion;MB removal rate increased when adsorption time or initial concentration of MB increasing;isothermal adsorption experiment disclosed that temperature rise made for MB removal and adsorption isotherm presented S type fitted with Freundlich equation(R~2＞0.89);Thermodynamic research suggested that the adsorption of MB onto IOCPCFM was spontaneous,endothermic and chemical reaction which was further proved by the adsorption activation energy value;the pseudo-second-order rate model and the intraparticle diffusion model well described adsorption kinetics of MB onto IOCPCFM and adsorption rate limiting step was film diffusion.In column mode,breakthrough time of adsorption column was calculated and forecasted by BDST mode,and a good agreement was found between model predictions and experimental data;because equilibrium time of column mode was shorter, equilibrium adsorption capacity from Thomas was lower than that of batch mode; some desorption of IOCPCFM after adsorption was achieved by dilute nitric acid(pH=3)and desorption effect was better in batch mode;adsorption removal mechanisms of MB included physics adsorption and chemical adsorption and chemical adsorption was major,while physics adsorption consisted of static adsorption and van der waals force adsorption,at the same time,chemical adsorption was composed of surface coordination-complex reaction and hydrogen bond formation.