Study On Preparation Of Granulated Composite Materials Of Rectorite For Treatment Of Copper Smelter Industrial Wastewater

Water-quenched slag is a kind of granular slag formed by quick water-cooling of molten substances from iron smelting furnace.It is a kind of industrial waste.Fly ash is a kind of solid waste like volcanic ash from coal-fired power plant.Rectorite is a layered silicate mineral consisted of dioctahedra of mica and montmorillonite with the ratio of 1:1.They can adsorb effectively contaminants of aqueous solutions.The research of their adsorption behavior becomes the focal point on intersectional subjects in recent years.But It has been found that the main problem in the treatment of wastewater using the powdered mineral adsorbing materials relates with the particle size of the materials.In order to get high adsorptive capacity,the materials used are normally very fine,which makes it difficult to separate the solids from solution after wastewater treatment,resulting in the formation of large volume of sludge.The powdered adsorbing materials cannot be used repeatedly and the substances adsorbed cannot be recovered.So they are applied very difficultly in the industry.Copper smelter industrial wastewater containing heavy metal ions such as Cu²⁺,Pb²⁺,Zn²⁺,Cd²⁺,Ni²⁺,etc is a kind of wastewater discharged in copper smelter production.Traditional treatment method of the wastewater is to neutralize by lime, which produces a lot of chemical sludge.Surrounding environment is secondary polluted.In order to solve the above-mentioned technique problems,develop environment-friendly adsorption materials,harness thoroughly pollution of copper smelter industrial wastewater,and utilize comprehensively resources,it is of particularly important signification for us to choose the preparation of granulated adsorption materials of water-quenched slag/rectorite or fly ash/rectorite composites for treatment of copper smelter industrial wastewater as the object of study.On the basis of an extensive survey of literatures,the preparation of granulated adsorption materials of water-quenched slag/rectorite or fly ash/rectorite composites and their application were systematically studied in the dissertation.The preparation process conditions of a compound nonmetallic granulated adsorption material were firstly explored with the aggregates of water-quenched slag or fly ash,the cementitious agent of rectorite,and the bubbling agent of industrial starch.XRD, SEM,FTIR,TG,etc techniques were adopted to characterize the composite nonmetallic granulated adsorption materials.Under the static and dynamic conditions, selective adsorption/desorption of different concentration heavy metal ions from copper smelter industrial wastewater by the compound nonmetallic granulated adsorption materials was studied.The dynamic equations,thermodynamic parameters, and mechanism of adsorption of the compound nonmetallic granulated adsorption materials for the removal of heavy metal ions from copper smelter industrial wastewater were studied.The main conclusions are as follows: Part one:Preparation and characterization of granulated adsorption materials1.The optimum preparation process conditions for granulated adsorption material of water-quenched slag/rectorite composite were a ratio of water-quenched slag to rectorite of 1:1,10%additive(industrial starch),50%water,and a calcination temperature of 400℃.Not only was the effect of granulated adsorption material the best,but also its spallation loss ratio was the lowest.Rectorite lost its adsorption water and interlayer water,which was observed from the TG pattern.The mineral phases were not changed as observed from the XRD pattern.Seen from SEM images,the granulated material had very good porous structure,the least pore size was about 5μm,the biggest pore size was about 80μm,and 90%pore sizes were from 30μm to 50um.The density of the granulated adsorption material prepared was 1.06kg/m³ and its porosity was 62.29%,with a water-absorption capacity of 58.82% and a compressive strength of 2.22 MPa.2.The optimum preparation process conditions for granulated adsorption material of fly ash /rectorite composite were a ratio of fly ash to rectorite of 1:1, 15%additive(industrial starch),50%water,and a calcination temperature of 500℃. Not only was the effect of granulated adsorption material the best,but also its spallation loss ratio was the lowest.Rectorite lost its adsorption water and interlayer water,which was observed from the TG pattern.The mineral phases were not changed as observed from the XRD pattern.Seen from SEM images,the granulated material had very good porous structure,the least pore size was about 5μm,the biggest pore size was about 70μm,and 80%pore sizes were from 20μm to 50μm.The density of the granulated adsorption material prepared was 0.95kg/m³ and its porosity was 64.93%,with a water-absorption capacity of 68.49%and a compressive strength of 2.15 MPa.3.The removal efficiency of Cu²⁺and the rate of spallation loss of granulated adsorption material of water-quenched slag /rectorite were almost identical with that of granulated adsorption material of fly ash /rectorite.But the calcination temperature of granulated adsorption material of water-quenched slag /rectorite was lower,and the additive dosage was less.Therefore,its production cost would be lower obviously than granulated adsorption material of fly ash /rectorite's in actual application.Part two:Treatment of copper smelter industrial wastewater with granulated adsorption materials under the static conditions,regeneration and utilization1.The optimal conditions of removal of heavy metal ions from copper smelter industrial wastewater with granulated adsorption material of water-quenched slag/rectorite composite were an amount of the granulated adsorbent of 0.05g/cm³,a reaction time of 40 minutes,and reaction temperature of 25℃at natural pH.The removal ratio of Cu²⁺,Pb²⁺,Zn²⁺,Cd²⁺and Ni²⁺was 98.2%,96.3%,78.6%,86.2% and 64.2%respectively,and the quality indexes of the wastewater after treatment conformed with the first level of integrated wastewater discharge standard (GB8978-1996).2.The optimal conditions of removal of heavy metal ions from copper smelter industrial wastewater with granulated adsorption material of fly ash/rectorite composite were an amount of the granulated adsorbent of 0.07g/cm³,a reaction time of 60 minutes,and reaction temperature of 25℃at natural pH.The removal ratio of Cu²⁺, Pb²⁺,Zn²⁺,Cd²⁺and Ni²⁺was 98.9%,97.5%,96.7%,90.2%and 79.1%respectively, and the quality indexes of the wastewater after treatment conformed with the first level of integrated wastewater discharge standard(GB8978-1996).3.The removal ratio of heavy metal ions from copper smelter industrial wastewater by granulated adsorption material of water-quenched slag/rectorite or fly ash/rectorite composite was slightly lower than that of powdered adsorption material, but it was very easy to separate the granulated adsorption materials from solution after wastewater treatment,and they could be reused.4.SEM images showed that the morphlogies of granulated adsorption material of water-quenched slag/rectorite or fly ash/rectorite composite saturated under the optimal adsorption condition of orthogonal tests were clear,and their tiny pores were not blocked,indicating that the granulated adsorption materials were calcined best, and they didn't spall when reacting with copper smelter industrial wastewater with weak acidity.5.The granulated adsorption material of water-quenched slag/rectorite composite after being used to treat the copper smelter industrial wastewater under the optimal condition could be desorbed effectively with 1mol/L sodium chloride(NaCl). Regenerated and reused for six times,the residual concentration of Cu²⁺,Pb²⁺,Zn²⁺, Cd²⁺and Ni²⁺of the wastewater treated with it was lower than the first level of integrated wastewater discharge standard(GB8978-1996).A mass loss of 2.2%and a compressive strength loss of 4.05%showed that the effect of granulation was quite good.6.The granulated adsorption material of fly ash /rectorite composite after being used to treat the copper smelter industrial wastewater under the optimal condition could be desorbed effectively with 1mol/L sodium chloride(NaC1).Regenerated and reused for six times,the residual concentration of Cu²⁺,Pb²⁺,Zn²⁺,Cd²⁺and Ni²⁺of wastewater treated with it was lower than the first level of integrated wastewater discharge standard(GB8978-1996)respectively.A mass loss of 2.6%and a compressive strength loss of 4.65%showed that the effect of granulation was good.7.The mass loss and compressive strength loss of the granulated adsorption material of water-quenched slag/rectorite composite regenerated was less than that of the granulated adsorption material of fly ash/rectorite composite regenerated, which showed that the effect of granulation of the granulated adsorption material of water-quenched slag/rectorite was better.Part three:Treatment of copper smelter industrial wastewater with granulated adsorption materials under the dynamic condition,regeneration and utilization1.According to integrated wastewater discharge standard(GB8978-1996),the exchange capacity of heavy metal ions from copper smelter industrial wastewater treated by the granulated adsorption material of water-quenched slag/rectorite composite adsorption column was 3.785mg/g and 3.207mg/g with a current velocity of 2mL/min and 3mL/min,and a penetration time of 48h and 30h.The residual concentration of Cu²⁺,Pb²⁺,Zn²⁺,Cd²⁺and Ni²⁺of the effluent was lower than the standard within 378.95 times and 355.26 times column volume.2.According to integrated wastewater discharge standard(GB8978-1996),the exchange capacity of heavy metal ions from copper smelter industrial wastewater treated by the granulated adsorption material of fly ash/rectorite composite adsorption column was 3.313mg/g and 2.996mg/g with a current velocity of 2mL/min and 3mL/min,and a penetration time of 46h and 28h.The residual concentration of Cu²⁺, Pb²⁺,Zn²⁺,Cd²⁺and Ni²⁺of the effluent was lower than the standard within 363.16 times and 331.58 times column volume.3.The smaller the current velocity,the better the treatmemt effect.Under the condition of low current velocity,heavy metal ions had more chance to contact with the granulated adsorption material of water-quenched slag/rectorite or fly ash /rectorite,and so the exchange capacity increased.4.According to integrated wastewater discharge standard(GB8978-1996),the exchange capacity of the granulated adsorption material of water-quenched slag /rectorite was bigger than that of the granulated adsorption material of fly ash /rectorite under the same condition.So the former could treat more copper smelter industrial wastewater.5.Under the conditions of current velocity of 12mL/min and current time of 4h, the exchange capacity of the granulated adsorption material of water-quenched slag or fly ash/rectorite regenerated with 1mol/L sodium chloride was 95.53%and 93.69% that of the newly-prepared granulated adsorption material respectively,indicating that their activities were recovered almost completely.6.After being regenerated and reused for six times,the exchange capacity of heavy metal ions adsorbed by the granulated adsorption material of water-quenched slag /rectorite reduced by 3.14%,while that by the granulated adsorption material of fly ash /rectorite reduced by 3.42%,which showed that the granulated adsorption materials regenerated had good treatment effect on copper smelter industrial wastewater.Part four:Mechanism of adsorption of heavy metal ions from copper smelter industrial wastewater removed by granulated adsorption materials 1.Under the static and dynamic conditions,the order of adsorption selectivity of the metal ions from copper smelter industrial wastewater adsorbed onto the granulated adsorption material of water-quenched slag/rectorite was as follows: Zn²⁺>Cu²⁺>Ni²⁺>Cd²⁺>Pb²⁺.Furthermore,it was found that Zn²⁺and Cu²⁺ showed a strong affinity for the material.The adsorption data fit Freundish equation: q_e=1.06C_e⁰.47.The reaction of adsorption was a first order reaction kinetics equation: C_t=C_o x e^-kt,namely lnC_Cu2+=-0.0112t-2.2895,lnC_Pb2+=-0.0126t-3.1407, lnC_Zn2+=-0.0074t+0.4714,lnC_Cd2+=-0.0047t-1.0888,lnC_Ni2+=-0.0038t-0.3713,which showed that the adsorption was mainly controlled by liquid membrane diffusion.The thermodynamic parameters was AH=-12.91kJ/mol,â–³S= -29.14J/(k·mol),AG=-4.21 kJ/mol,which showed that the decrease ofâ–³G was the main driving force for the removal of the heavy metal ions.2.Under the static and dynamic conditions,the order of adsorption selectivity of the metal ions from copper smelter industrial wastewater adsorbed onto the granulated adsorption material of fly ash/rectorite was as follows:Zn²⁺>Cu²⁺> Ni²⁺> Cd²⁺> Pb²⁺.Furthermore,it was found that Zn²⁺and Cu²⁺showed a strong affinity for the material.The adsorption data fit Freundish equation:q_e=l.02C_e ⁰.49.The reaction of adsorption was the first order reaction kinetics equation:C_t=C_o x e^-kt,namely lnC_Cu2+=-0.0094t-1.4342,lnC_Pb2+=-0.0166t-2.1868,lnC_Zn2+=-0.0082t +0.2111,lnC_Cd2+=-0.0029t-1.1958,lnC_Ni2+=-0.0025t-0.4744,which showed that the adsorption was mainly controlled by liquid membrane diffusion.The thermodynamic parameters wasâ–³H=-11.98kJ/mol,â–³S=-26.82J/(k·mol), AG=-3.97 kJ/mol,which showed that the decrease ofâ–³G was the main driving force for the removal of the heavy metal ions.3.At a calcination temperature of 400℃or 500℃,the mineral phases of water -quenched slag,fly ash and rectorite were not changed,and the crystal structure of rectorite was not destroyed.The mechanism of adsorption of the heavy metal ions from copper smelter industrial wastewater onto the granulated adsorption materials of water-quenched slag/rectorite or fly ash /rectorite was mainly their synergistic adsorption action.Certainly,the bubbling function caused by the burning of industrial starch was essential.The research results have important theoretical meaning for composite nonmetallic granulated adsorption materials,removal and recovery of heavy metals from wastewater.At the same time,it will guide profitably the engineering design of treatment of copper smelter industrial wastewater and other heavy metal-containing wastewater.