Research On COD Rich Industrial Wastewater Adsorption And Degradation By Nano Ferrite On Active Carrier

The Printed Circuit Board (PCB) industry is an important electronic industry which is in the golden period of development in China. PCB are widely used in many fields, such as electronic equipments. The PCB industry produces many kinds of wastewater. One of them is a high concentration organic wastewater, called developer. The Chemical Oxygen Demand (COD) of this wastewater is extremely high and hard to degrade. this wastewater is usually treated by adding acid to decrease the COD, but the process is ineffective, the remaining COD after treatment may not reach the wastewater discharge requirement.Active carbon is a good adsorbent with strong absorbability, because of its well developed porous structure and huge specific surface area, and has been widely used in water treatment. The main raw material of active carbon is wood. To protect the forest resources, we chose another material to make active carbon. We took into consideration that our country has a high quantity of agriculture wastes, such as rice husk. Rice husk has a high carbon matter content, so it can be made into active carbon after certain treatments.Nano material has many special properties that bulks do not have, such as surface properties, small size properties, macroscopic quantum properties, quantum size properties and Coulomb blockade properties. It has been widely used in the fields of catalysis and optics, and the nanotechnology is a research focus. Ferrite is a kind of complex oxides. Spinel ferrite has been used in catalysis, electromagnetic absorption and so on. The ferrite can catalyzed oxidative degradation of organics.Using rice husk as raw material, we produced active carrier with a high specific surface area and porous structure though hyperthermia carbonization and activation. We then produced a series of ferrites on active carrier (including MnFe₂O₄, CoFe₂O₄ and MnFe₂O₄ produced in N₂ atmosphere). An attempt was made to dope the rare earth element (REE) Ce into the lattice of ferrite. The results of XRD and SEM supported the conclusion that active carrier with ferrite was successfully.produced. however REE doping was unsuccessful, the element Ce was not doped into the lattice of ferrite and this should be improved in the future work.Studying the developer wastewater provided by YanTat Printed Circuit (ShenZhen Enda) Co.,Ltd, we studied the effect of active carrier and ferrite on active carrier (FAC) when treating wastewater, compared the ability of different kinds of ferrite, and discussed the impact of existence of REE. Through a series of dosage levels and time course experiments, the optimal methods for treating the COD rich wastewater were determined. The detailed results are as follows:1. Both the active carrier and FAC can reduce the COD of wastewater efficiently, the removal rate of COD can reach 65 %. The active carrier have adsorbability only, while FAC has both adsorbability and catalytic ability. While adsorbing the COD rich material, the nano-ferrite oxidized the organics. The FAC thus has improved application prospects compared to the active carrier.2. When the active carrier contained MnFe₂O₄ and CoFe₂O₄ respectively, the effects to treat wastewater were similar. The doping of REE did not play any role. Considering that the price of cobalt nitrate and cerium nitrate are 5-10 times that of manganese nitrate, active carrier with MnFe₂O₄ is the best choice.3. The remaining COD of wastewater after treatment did not changes significantly as the dosage of FAC increased. Clearly, the residual COD is resistant to degradation and difficult to remove. When the ratio of the dosage of FAC and the wastewater is 3:200, the best result was obtained, the COD of wastewater decreased by more than 70 %.4. When microwave irradiation was tested as an additional treatment to wastewater, the remaining COD of the wastewater decreased in the first 6 mins. At later time points, the COD did not change significantly. Thus, when using microwave irradiation as an additional treatment, the best treatment time is 6 mins.5. When adding aerated air into the wastewater as an additional treatment., the remaining COD of wastewater decreased sharply in the first 6 mins, but after treatment for 6 mins, the COD started to rise slowly. Thus, when using aerated air as an additional treatment, the best treatment time is 6 mins.6. The FAC that we produced can be recycled multiple times. The recoverability increased its utilization and reduced the costs.