Rapid Purfification Of Cadmium Pollution From Farmland Irrigation Water By Fiber Ball Filter Materials

In recent years, with the rapid development of China's economy, water resources shortage has become even worse. Under this condition, irrigation of polluted water has become the main source of farmland irrigation. A new water purification theory has been put forward targeting the deficiency of regular artifacts of polluted water irrigation. A front purification device has been developed, and this device will be applied before polluted water flowing into farmland. By filtering, intercepting, and absorbing with interior materials, this device can deal with heavy metals contained in polluted water with efficient and emergent disposal.By comparison, this thesis selects fiber-ball filter media that can filter suspended solids efficiently as test materials under the condition of high speed filtering. Through purification simulation of irrigation water, the research explores factors like the height of filtering device, pH of water, diameter of filtering materials, and speed of filtering to acquire the impact that fiber-ball filtering materials might have. Through changing the character of potassium permanganate, we acquire the improved fiber-ball filtering materials of Cd2+ with great absorbing ability. Through observing the dose of absorbing materials,preliminary pH of solution, time of reaction, initial ion concentration of solution, we acquire the impact that they have on Cd2+. Besides, the thesis also adopts scanning electron microscope, infrared spectroscopy and X-ray scattering techniques to analyze the feature of surface structure of fiber-ball filtering materials.Main research results are as follows:(1) Through dynamic simulation experiment of Fiber-ball filtering materials and single factor analysis, we observed the impacts caused by the height of filter materials, diameter, pH number of water and speed of filtering. Filter height is the key factor of filtering effect, but it does not mean that higher filtering height will guarantee the quality of water. Actually, if the filtering layer is too high, it will influence the speed of filtering. At the same time, some of the filtering materials can not be used completely. Through the comparison experiment of pH, fiber-ball filtering materials does not endure alkali. In alkaline water, fiber-ball filtering materials are easy to be undermined, and the filtering effects will turn worse. The diameter of filtering materials has influence on filtering effects. If the diameter is too big, the porosity will be higher, and the filtering effects will be not as good as expected; if the diameter is too small, the porosity will be smaller, and the filtering effects will be better. Through comparison experiment of filtering speed, under the condition of high-speed filtering, the fiber-ball filtering materials, suspended solids and heavy metals can be filtered with efficiency. This is conformed with the flowing speed of irrigation in the process of farmland irrigation. Under the speed of 20m/h, diameter of 30 mm, initial water pH number 7, filtering height 40 cm, the filtering effects will be the best, and the cycle will be the longest. Removal rate of SS can reach 90%.(2) After analysis of fiber-ball filtering materials, the thesis found that the surface of fiber-ball filtering materials becomes looser, and the specific surface area and porosity of fiber-ball filtering materials are enlarged. The attractive on the surface increases more active group. Connecting more functional groups on the chemical boards that is interrupted, all of these can improve the absorbing ability of heavy metal ion of fiber-ball filtering materials.(3) When the temperature is 25?, Cd2+'s balancing time of fiber-ball-filtering materials is 10h. When the pH number is central, the absorbing effect is the best, and the best absorbing dose is 1g/L; the absorbing amount of Cd2+ will increase with the increase of Cd2+ concentration. When the initial concentration is 1000?g/L, the largest absorbing capacity of acquiring the material is 535.47?g/g. Through the comparison experiment of absorbent, the conclusion is that under the condition of not breaking surface structure of filtering materials, EDTA has the best absorbing effect.(4) This thesis carries out matching of pseudo-first order kinetic model and pseudo-second order kinetic model respectively toward the data of adsorption kinetics. The absorbent's absorbing process of Cd2+ is relatively conformed with first model of dynamics; after changing the features, the Langmuir data of Cd2+ toward fiber-ball filtering materials are matched by Langmuir model and Freundlich model. The absorbing process is more conformed with Langmuir model.