Study On Degradation Of Coking Wastewater By The Waste Iron-bearing Dust

The iron-bearing dust is a kind of solid wastes with complex components andlarge quantities of material available, which is derived from the process ofsteel-making. Up to now, most of the dust is stockpiled on-site, whereas smallamounts of the dust are used for recycling in China. These methods not only engross alarge amount of land, but also seriously pollute the environment. Thus, its effectiveutilization can reduce the land occupancy and eliminate the environmental pollution.Consequently, its comprehensive utilization can also bring social and environmentalbenefits.The coking wastewater is a kind of industrial organic wastewater with widesource, large displacement, complicated composition and toxicity. As a result, it isvery difficult to be degraded. A lot of phenols, polycyclic aromatic hydrocarbons,heterocyclic compounds in the coking wastewater are harmful to the environment andhuman health. As the increasingly stringent environmental requirements and thegrowing environmental awareness in our country, seeking an economic and efficientway to degrade the coking wastewater is the key issue in the treatment of this kind ofwastewater.Fenton/Fenton-like oxidation methods show the unique advantage and practicalapplication prospect in the field of wastewater treatment, by producing strongoxidizing of hydroxyl radicals (OH) to degrade organic pollutants. The majorcomponents of Fe3O4and Fe2O3in the iron-bearing dust can be dissolved into theferrous and ferric ions in an acidic solution, and then Fe2+, Fe3+with hydrogenperoxide can form heterogeneous Fenton reaction system/Fenton’s type reactionsystem. The phenols, polycyclic aromatic hydrocarbons, heterocyclic compounds inthe coking wastewater were regarded as the main research object in this paper. Thedegradation conditions of phenol, naphthalene, thiophene and actual cokingwastewater were investigated in detail. The effects of the pH value, dosage of H2O2, amount of iron-bearing dust,reaction temperature and time on removal rate of phenol, naphthalene, thiophene andactual coking wastewater were discussed by single factor control method. Under theoptimum experimental conditions of pH is3, dosage of H2O2is3.00mL/L, amount ofthe dust is15.00g/L, reaction temperature is40℃, reaction time is12h,97.34%ofremoval rate of the initial concentration of1000mg/L phenol in wastewater wasachieved. Under the optimum experimental conditions of pH is3, dosage of H2O2is4.00mL/L, amount of the dust is6.00g/L, reaction temperature is35℃, reactiontime is4h,98.58%of removal rate of the initial concentration of100mg/Lnaphthalene in wastewater was achieved. Under the optimum experimental conditionsof pH is3, dosage of H2O2is3.00mL/L, amount of the dust is5.00g/L, reactiontemperature is30℃, reaction time is4h,78.22%of removal rate of the initialconcentration of100mg/L thiophene in wastewater was achieved. The optimumexperimental conditions of the initial COD concentration of3000mg/L actual cokingwastewater: pH is3, dosage of H2O2is6.00mL/L, amount of the dust is8.00g/L,reaction temperature is35℃, reaction time is4h, the removal rate of COD andchromaticity on the actual coking wastewater reached58.64%and75.65%respectively. The intermediate products of phenol, naphthalene, thiophene wereanalyzed by high performance liquid chromatography (HPLC) and the possiblemechanisms of degradation of the three kinds of materials were discussed. Finally, theXRD patterms of the pretreatment iron-bearing dust and treated dust werecharacterized.