Method for preparing nanoscale carbon-coated magnetic ferroferric oxide by taking backwashing iron mud as raw material
The technical field is as follows:
the invention belongs to the field of water treatment waste recycling and inorganic fine chemical industry.
Background art:
in recent years, magnetic ferroferric oxide materials have been widely used in the fields of water treatment, catalysis, dyeing, high magnetic recording, biosensing and the like due to their special physicochemical properties such as electrical and magnetic properties. The nanometer-level ferroferric oxide has larger specific surface area, stronger catalytic activity and the like due to the fact that the particle size of the nanometer-level ferroferric oxide is in the nanometer level, so that the nanometer-level ferroferric oxide draws the attention of a plurality of researchers, and explores a plurality of methods for preparing the nanometer-level magnetic ferroferric oxide.
The magnetic ferroferric oxide is not stable in chemical property, so that the magnetic ferroferric oxide is not suitable for long-time storage; furthermore, the particle agglomeration phenomenon is liable to occur due to the influence of the acting force (van der Waals force and magnetic force) existing on the particle surface. Therefore, the research on the surface modification of the nano magnetic ferroferric oxide particles is carried out. Recently, the ferroferric oxide material coated by carbon-based shell is concerned about due to larger specific surface area and more stable chemical property, and a plurality of related researchers explore a plurality of methods for preparing nano-scale carbon-coated magnetic ferroferric oxide by pure chemicals.
The invention relates to a method for preparing nano-scale carbon-coated magnetic ferroferric oxide by taking backwashing iron mud as a raw material. The water treatment plant using the underground water with the excessive iron as a water source can lead the ferrous iron in the water body to generate stable iron oxide solids (the main components are indefinite ferric hydroxide, alpha-FeOOH and gamma-FeOOH with poor crystallization) by a biological purification filter layer method, thereby being intercepted by the filter layer, purifying the water quality, and finally discharging the generated iron oxide along with the back flush of the filter tank. A large number of iron-containing underground water treatment plants in China generate a large amount of iron-containing mud backwashing water every year, and the direct discharge can cause serious pollution to water bodies. The invention tries to synthesize the nano-scale carbon-coated magnetic ferroferric oxide by using the backwashing iron oxide (also called iron mud) as an iron source, thereby not only saving the cost for treating the waste iron mud, but also realizing the resource recycling of the iron mud.
The invention content is as follows:
the invention is realized by the following technical scheme:
a preparation method of nanoscale carbon-coated magnetic ferroferric oxide comprises the following two steps: comprises (1) purification and concentration of iron ions and (2) preparation of nano-scale carbon-coated magnetic ferroferric oxide;
(1) and (3) purifying and concentrating iron ions: standing and precipitating the backwashing wastewater of the biological filter for removing iron and manganese in the water plant for 2-5 days, and drying the sludge at the bottom for subsequent use. Adding the iron mud into hydrochloric acid, continuously stirring for 1 hour, standing for 8-14 hours, taking out supernatant after solid matters are precipitated, adding NaOH solution to adjust pH so that iron ions in the solution generate precipitates, after solid-liquid separation, adding hydrochloric acid again to dissolve the precipitates, evaporating and concentrating the obtained solution, and waiting for subsequent reaction for later use.
(2) Preparing nano-scale carbon-coated magnetic ferroferric oxide: dissolving glucose and urea in the prepared iron solution, and magnetically stirring for 30-60 min to make the solution free of solid matter residue. Transferring the solution to a polytetrafluoroethylene lining high-pressure reaction kettle, screwing the reaction kettle, and sealing the kettle body. Then the reaction kettle is placed into an oven and kept at 200 ℃ for 12-16 hours at 180 ℃. Naturally cooling the reaction kettle to room temperature, opening the reaction kettle, taking out the generated black precipitate, dispersing for 5min under ultrasonic wave, washing with distilled water for 5-7 times, and separating water from the product by an external magnetic field during the washing process. Finally, the obtained product is put into a drying oven and dried for 4 to 8 hours at the temperature of between 50 and 60 ℃ to obtain the nano-scale carbon-coated magnetic ferroferric oxide.
Further, the raw material is derived from waste iron mud of water treatment plants or other industrial waste iron oxides (mainly ferric iron).
Further, the concentrations of hydrochloric acid and NaOH used in the step (1) are 3mol/L and 1mol/L, respectively.
Further, the added iron mud and the hydrochloric acid can be mixed according to the proportion of 12-15g of iron mud: 100-120ml hydrochloric acid.
Further, NaOH solution is added in the step (1) to adjust the pH value to 3.1-3.7, so that most of iron ions in the solution are precipitated.
Further, the mass ratio of the iron ions, the glucose and the urea in the hydrothermal reaction process in the step (2) is as follows: 0.009-0.01mol:0.01-0.012mol:0.1-0.12 mol.
Furthermore, in the step (2), the drying temperature can be 60 ℃, and the drying time can be 5 hours.
The nanometer carbon-coated magnetic ferroferric oxide powder can be prepared by using the back washing iron mud as the raw material through the process, and the method has the following advantages: in the preparation process, all iron elements come from water treatment waste (back washing iron mud), so that the resource utilization of the waste is realized.
Secondly, the generated carbon-based coated ferroferric oxide powder is more stable and is more beneficial to storage in natural environment.
Description of the drawings:
FIG. 1 is a TEM image of a nanoscale carbon-coated magnetic ferroferric oxide obtained by the present invention;
FIG. 2 is a TEM image of a carbon coating layer of nanoscale carbon-coated magnetic ferroferric oxide obtained by the present invention;
the specific implementation mode is as follows:
a preparation method of nanoscale carbon-coated magnetic ferroferric oxide comprises the following two steps: comprises (1) purification and concentration of iron ions and (2) preparation of nano-scale carbon-coated magnetic ferroferric oxide;
(1) and (3) purifying and concentrating iron ions: standing and precipitating the backwashing wastewater of the biological filter for removing iron and manganese in the water plant for 2-5 days, and drying the sludge at the bottom for subsequent use. Adding 15g of iron mud into 100ml of 3mol/L hydrochloric acid, continuously stirring, standing, taking out supernatant after solid substances are precipitated, adding 1mol/L NaOH solution to adjust the pH value to 3.3 so that iron ions in the solution generate precipitates, after solid-liquid separation, adding hydrochloric acid again to dissolve the precipitates, evaporating and concentrating the obtained solution, detecting the concentration of the iron ions in the solution to 14g/L, and waiting for subsequent reaction for later use.
(2) Preparing nano-scale carbon-coated magnetic ferroferric oxide: about 3g of glucose and 12g of urea were dissolved in 60ml of the iron solution prepared above, and stirred. The solution was transferred to a 100ml teflon lined autoclave. The reaction vessel was then placed in an oven and held at 180 ℃ for 14 hours. Naturally cooling the reaction kettle to room temperature, opening the reaction kettle, taking out the generated black precipitate, washing with distilled water for 5-7 times, and separating water from the product by an external magnetic field during washing. And finally, drying the obtained product to obtain about 2.5g of nano-scale carbon-coated magnetic ferroferric oxide. The specific saturation magnetization of the obtained product at room temperature can reach 33.51emu/g, solid-liquid separation can be easily realized from a water body under an external magnetic field, and the product can be stored for at least more than 10 months under a sealed condition.