Preparation Of Municipal Sludge/biomass Co-blended Modified Materials And Their Performance In Adsorption Applications

Heavy metals and aromatic hazardous substances are the key control targets for water pollution treatment.The adsorption treatment is still the most practical method for this type of wastewater treatment technology,and its key factor is adsorbent material.The activated sludge method is widely used for urban domestic wastewater treatment.However,the residual sludge is a by-product of this process,which has a large yield and may form secondary pollution if not treated properly.In the paper,a series of novel wastewater treatment adsorbent materials[sludge/potato（SL/PO）,sludge/corn straw（SL/CS）]were prepared by activation and composite modification of the residual sludge of Xiaohe District wastewater treatment plant in Guiyang City,and their applied treatment effects on two types of wastewater containing Cr（VI）and nitrobenzene were studied.To improve the recycling performance of the adsorbent materials,the products were further mixed with polymeric sodium alginate（SA）mixed and molded to prepare water treatment composite adsorbent materials（SL/PO/SA）with certain size and shape.The main research work and achievements are as follow:1.Analysis experiment of physicochemical properties of raw materials.The physical and chemical properties of sludge,potatoes and corn straw were analyzed,and it was found that the carbon content of sludge was 12.52%（w%）,and the heavy metal content was lower than the standard limit of sludge sludge.In addition,the carbon content of potatoes and corn straw were 40.06%and 42.93%,respectively,which could be blended with sludge to prepare adsorbent materials.2.The preparation of SL/PO adsorption material.Through preliminary comparison experiments,KOH solution was chosen as the activator to prepare the adsorbent material.The single factor experiments were carried out to investigate the effects of potato addition,activation temperature,activation time and activator concentration on the adsorbed iodine value.The optimal preparation conditions were50wt%potato addition,activation temperature 650℃,activator concentration 3 mol/L and activation time 45 min,and the adsorbed iodine value of SL/PO was obtained up to 343.73 mg/g.The SEM,BET,TG/DSC,IR and XRD results show that the O-H bonding peak of SL/PO was stronger than that of SL,led to the chemical activity increasing.The surface of sample had obvious pore structure,the specific surface area was increased as the roughness increasing.In addition,the thermal stability of SL/PO was best,and there were Si O₂ diffraction peaks.3.The application of SL/PO in treatment of contaminants.The experimental condition,such as effects of dosage,p H,adsorption time and initial concentration on the removal of Cr（VI）and nitrobenzene in water by SL/PO were investigated.It was found that the removal rate of Cr（VI）and nitrobenzene in water by SL/PO was increased with the increase of dosage and adsorption time.Meanwhile,the effect of p H on the removal effect of Cr（VI）adsorption in water was greater,and the removal rate reached 99.96%at p H 1.We also found that the removal rate of nitrobenzene in water increased with the increase of p H,and then leveled off,and the optimum p H was 5.The optimal experimental conditions were obtained by treating Cr（VI）and nitrobenzene wastewater containing 100 mg/L at 25℃.The pollutant removal rates were 99.99%and 98.73%with SL/PO dosage of 0.125 g and 0.15 g,p H values of 1and 5,and adsorption times of 90 min and 210 min.The adsorption kinetics and thermodynamics of the SL/PO treatment process for Cr（VI）and nitrobenzene containing wastewater were initially investigated.The adsorption processes of Cr（VI）and nitrobenzene by SL/PO were in accordance with the quasi-secondary kinetic equations,with R² above 0.999.The isothermal adsorption process of SL/PO on Cr（VI）was in accordance with the Langmuir isothermal adsorption equation,and unimolecular layer adsorption occurred.The isothermal adsorption Freundlich equation for SL/PO on nitrobenzene is a better fit with R² obove 0.99 and process heat absorption.The desorption of the adsorbent materials with Na OH solution showed79.48%and 72.47%for Cr（VI）and nitrobenzene.The removal of Cr（VI）and nitrobenzene by the desorbed SL/PO were 89.97%and 84.37%,respectively.The wastewater treatment comparison experiments between SL/PO and activated carbon powder revealed that the adsorption capacity of SL/PO for Cr（VI）and nitrobenzene was comparable to that of commercially available activated carbon powder.4.The preparation of SL/CS adsorbent materials and treatment of wastewater experiments.The SL/CS adsorbent material was prepared under the experimental conditions:50%corn straw addition,650℃activation temperature,3 mol/L activator concentration and 45 min activation time,and the product adsorption iodine value was360.26 mg/g.The SEM,BET,TG/DSC,IR and XRD results showed that the O-H bonding peak of SL/CS was stronger than that of SL,the chemical activity was increased,the surface had obvious pore structure,the roughness was increased,the specific surface area was increased,the thermal stability of SL/CS was better,and there were Si O₂ diffraction peak.The effects of product dosage,p H,adsorption time,and initial concentration on the removal of Cr（VI）and nitrobenzene from water by SL/CS were investigated,and the effect pattern was similar to SL/PO above.The optimal experimental conditions were SL/CS dosage of 0.10 g and 0.10 g,p H values of 1 and 3,and treatment times of 60 min and 90 min,with pollutant removal rates of99.99%and 98.87%.The processes of Cr（VI）and nitrobenzene adsorption by SL/CS were in accordance with the quasi-secondary kinetic equation,and the R² reached above 0.9999.The isothermal adsorption of Cr（VI）by SL/CS is consistent with the Langmuir equation,and the isothermal adsorption of nitrobenzene by SL/CS is consistent with the Freundlich equation.The correlation coefficients were greater than0.99,and the adsorption processes were all heat absorption.The desorption rates of SL/CS for Cr（VI）and nitrobenzene were 80.46%and 87.27%,respectively.The wastewater removal rates of SL/CS for Cr（VI）and nitrobenzene after desorption were89.92%and 87.27%.5.The preparation of SL/PO/SA and its application effect experiment.The SL/PO/SA was prepared under the experimental conditions of SL/PO 0.45 g,sodium alginate solution 100 m L（3%mass fraction）,porogenic agent Na Cl 2.4 g,1%（w%）curing agent Ca Cl₂ 300 m L.The SEM and IR analysis showed that SL/PO/SA composite microspheres with certain size and shape were successfully prepared,which have rough surface,certain pore structure and contain a large number of oxygen-containing groups with adsorption activity.The removal rates of composite microspheres for Cr（VI）and nitrobenzene containing wastewater were 84.54%and86.99%,which were somewhat lower than the adsorption effect of SL/PO.The stability of the productions showed that the microspheres were stable at p H 1～13,temperature 15～55℃and immersion 1～20 days.After repeated experiments,the desorption rates of the microspheres for Cr（VI）and nitrobenzene were 80.03%and73.44%,and the regeneration adsorption removal rates were 75.63%and 74.54%,with better recycling effect.