Study On The Treatment Of Dyeing Wastewater By Modified Ferric Hydroxide

For its large amount of water, changing components, high color, highly toxic, biodegradable, et al, dyeing wastewater has become one of the intractable industrial wastewater. So developing high efficiency, cheap and easy bleaching technology has always been the focus of the problem in dyeing industry. Ferric hydroxide has large specific surface area and strong adsorption property, so the purpose of this thesis was to take advantage of the unique physical properties of ferric hydroxide to load it on traditional adsorbents and then explore the removal mechanism of methylene blue by the compounds. Compared adsorption effect of different types of composite adsorbent and ultimately select two advantageous combinations as ferric hydroxide-modified adsorbent materials, on this basis, analyzed the features of carriers before and after loading ferric hydroxide using a variety of methods BET, SEM, XRD and so on. Through batch experiments, analyzed treatment effect of methylene blue dyeing wastewater by composite adsorbent of initial pH, adsorbent dosage, adsorption time and temperature, initial concentration of metal salt and other factors and finally established isothermal adsorption and dynamics models.The following achievements were made in this thesis:The carrier screening experimnets showed activated carbon and zeolite were more suitable than quartz sand, straw for being made compounds of ferric hydroxide adsorbent and applied to the treatment of methylene blue dyeing wastewater.Characterization results of activated carbon after ferric hydroxide loaded illustrated that the compound of activated carbon/ferric hydroxide was rougher than the original activated carbon and increased much microporous.The specific surface area was increased to twice and no new diffraction peaks was produced, indicating ferric hydroxide was acted as noncrystalsto form to be loaded on the surface of activated carbon.The adsorption capacity of ctivated carbon/ferric hydroxide compound was 62.5667 mg/g by the Langmuir equation,1/n was obtained between 0.1 to 1 by the Freundlich equation, showing that the adsorption of methylene blue by activated carbon/ferric hydroxide compound belonged to preferential process. The adsorption process of methylene blue by activated carbon/ferric hydroxide compounds meeted to the pseudo-second-order kinetic model.The investigation of factors on adsorption of methylene blue by activated carbon/ferric hydroxide composite adsorbent found that the optimum experimental condition of adsorption of methylene blue by activated carbon/ferric hydroxide composite adsorbent was:when processing volume of 100mL methylene blue solution of 150 mg/L, the test temperature was room temperature, pH 6 to 12, the dosage of activated carbon/ferric hydroxide compound was 4g/L, the adsorption time of oscillation was 60min, the removal rate reaching of 96.89%.Characterization results of zeolite after ferric hydroxide loaded illustrated that the conpound of zeolite/ferric hydroxide was rougher than the original zeolite and increased much microporous.The specific surface area was increased to fourfold.The adsorption capacity of zeolite/ferric hydroxide compound was 35.4986 mg/gby the Langmuir equation,1/n was obtained between 0.1 to 1 by the Freundlich equation, showing that the adsorption of methylene blue by zeolite/ferric hydroxide compound belonged to preferential process. The adsorption process of methylene blue by zeolite/ferric hydroxide compounds meeted to the pseudo-second-order kinetic model.The investigation of factors on adsorption of methylene blue by zeolite/ferric hydroxide composite adsorbent found that the optimum experimental condition was:when processing volume of 100mL methylene blue solution of 100 mg/L, the test temperature was room temperature, pH was 9, the dosage of activated carbon/ferric hydroxide complexes was 6g/L, the adsorption time of oscillation was 30min, the removal rate reaching of 92.43%.Processes of two ferric hydroxide modified adsorbents are relatively simple. The adsorption effect of zeolite/ferric hydroxide compound was slightly worse than that of activated carbon/ferric hydroxide compound, but compared to the natural zeolite, the entire process of loading greatly improved adsorption efficiency. Because of itsactivated carbon’s superior performance, a wide range of sources of raw materials for its preparation, therefore, the both ferric hydroxide modified adsorbents can be obtained good application and promotion in the tretment of dyeing wastewater.