| Dye wastewater is characterized by complex composition, high levels of color,suspended solids and dissolved organic matter. Due to its characteristics, the treatmentof dye wastewater is the key to treating industrial wastewater. Disperse dye, reactivedye, acid dye, basic dye often coexist in the dye wastewater and differ incharacteristics, which make it difficult to achieve a desired treatment efficiency by asingle approach. However, the widely used complex presented process the issues oflarge area, complicated running and operational management. This study, based on theparticle hydraulic classification theory, has constructed a coagulation-adsorptionintegration fluidizated bed and an oxidation-adsorption integration fluidizated bed.Those are new processes of ease of operation.Coagulation parameters optimization results indicate that the velocity gradient inthe turbulent state is invalid, and thus we optimized the coagulation kineticsparameters by selecting Kaolin clay as the target pollutants. In the four commonlyused coagulation kinetic parameters, we found only Eula number (Eu) exhibits thesame trend with Kaolin clay removal rate under different operating conditions, and Euonly relates to particle density, particle size, coagulation time and so on. Therefore,Eu is the optimal operational factors for controlling fluidizated bed reactor.The bottom of the fluidizated bed was filled with heavy granular silica gels orceramics, and the upper part of the fluidizated bed with light granular activated carbon.Due to different particles have different hydraullic fluidization characteristics,coagulation-adsorption or oxidation-adsorption can be established. Silica gels andactivated carbons filled the coagulation-adsorption fluidized bed by a series of ratiosof350:0,250:100,175:175,100:250,0:350. Composite dye wastewater was made upof50mg/L disperse red,80mg/L acid yellow and80mg/L reactive brilliant blue.Meantime,200mg/L coagulant poly aluminium chloride (PAC) were added into thatdye wastewater. When the fluidized bed was filled with activated carbon without PAC,only adsorption process occurred. It resulted in an ideal removal efficiency of acid yellow, but a low value of disperse red which accompanied by63.3%COD removalefficiency. As long as only coagulation reaction occurred, the disperse red can bealmost completely removed and COD removal rate was80.6%, while the acid yellowremoval efficiency was not ideal. In the coagulation-adsorption integrated fluidizedbed, acid yellow removal efficiency increased with the activated carbon dosage. Theratio of silica gel to activated carbon at100:250resulted in an optimal removalefficiency of dyes and96.8%COD removal efficiency. The larger Eu value generatedby activated carbon than silica gel can effectively protect flocs produced bycoagulation from damage. The flocs size continued to grow from65.30μm to85.49μm, thus can obviously enhance coagulation and flocculation efficiencies..In the oxidation-adsorption fluidized bed, composite dye wastewater consisted of50mg/L disperse red,80mg/L acid yellow and80mg/L reactive brilliant blue. Thecomposite dye wastewater’s pH was adjusted to3. The fluidized bed was filled with175mm height of ceramics and activated carbons, respectively. Added0.59g ofFeSO4·7H2O in the composite wastewater, and then start counting time when added3.57mL H2O2. In the first30s of the reaction, acid yellow was removed completely,and27.93%disperse red and55.80%reactive blue were removed.10min later,disperse red and reactive blue removal efficiencies increased to79.76%and79.80%,respectively. It is evident that oxidation-adsorption integrated reaction had a betterremoval efficiency of these three different types of dyes than a single oxidation oradsorption in a relatively short period of time. In respect to Fenton reaction, the CODremoval of only activated carbons filled was higher that of only ceramics filled. Thisis because activated carbons can adsorb partially Fenton-oxidized organic matters wand further reducing the COD of the effluent. In addition, the XPS and XRD resultsshowed the two major kinds of presence of iron:(1) FeOOH loaded in the ceramicand (2) FeSO4(H2O) adsorbed in the activated carbon. |
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