The Absorbtion Of Modified Rice Husk Ash To Heavy Mental Chromium And Mercury In Water

Wastewater generated in mining, electroplating, battery manufacturing, metallurgy and many other industries has high content of heavy metal mercury and chromium. Heavy metal mercury and chromium has the features:great toxicity, strong bioaccumulation and refractory. The inappropriate disposal method of wastewater containing heavy metal by many factories and enterprises leads to many soil and water pollution incidents. It is a potential threat to of human, environment, wildlife health and safety because of the presence of these toxic and carcinogens. Therefore, we must find cost-effective ways to remove mercury and chromium in industrial wastewater, so that water source can serve humanity better.Traditional mercury and chromium wastewater removal process is costly and complicated. In contrast, bio-sorption is a very simple method. It is operated easily and cheap, and the ultimate adsorption effect is not weaker than any other methods. The most important thing is free from contamination. Bio-sorption method in heavy metals removal has gradually received attention from researchers, and it is concerned by scholars as the leader in adsorption field.We use a common biomass material (rice husk ash made from burned rice husk) from agricultural wastes as adsorbent in adsorption process. Adsorption effect of modified rice husk ash against heavy metal chromium ions and mercury ions was investigated. Sodium hydroxide and hydrofluoric acid are taking to modify rice husk ash, Industrial wastewater containing much mercury and chromium was discussed using modified rice husk ash as adsorbent by single factor and orthogonal experiment.The main by-product produced in production and process of rice husk is rice husk. So the rate of production is very high in world, especially in the northeast. It is cheap and available. Meanwhile, rice husk ash formed from high-temperature calcination has a nice function of absorbing heavy metal. Therefore, rice husk ash adsorbs industrial wastewater containing much mercury and chromium as adsorbent, which can effectively achieve the purpose of waste control by waste. The method is of practical significance in actual wastewater treatment process.From basic characterization method-BET Adsorption, we find that:specific surface area of RHA/HF (rice husk ash simply treated by hydrofluoric acid) is the largest, specific surface area of RHA/NaOH (rice husk ash simply treated by sodium hydroxide) and specific surface area of RHA (rice husk ash by direct high-temperature calcination) is the smallest. Then, we finally confirm selecting RHA/HF as the ultimate adsorbent adsorption by means of infrared and X-ray diffraction characterization.Orthogonal experimental results on the basis of single factor showed that the optimum conditions of RHA/HF absorbing wastewater containing chromium are as follows:when adjusting solution to pH 5, the amount of rice husk ash is 20 g/L and the speed is maintained as constant 120 r/min; when the adsorption time is 120 min, the rice husk ash treated by hydrofluoric acid absorbs chromium most effectively, the initial concentration of chromium in wastewater is 5 mg/L and the maximum adsorption efficiency can reach 74.88%.Likewise, when adjusting solution to pH 6, the amount of rice husk ash is 30 g/L and the speed is maintained as constant 130 r/min; when the adsorption time is 100 min, RHA/HF absorbs wastewater containing chromium most effectively, the initial concentration of chromium in wastewater is 3 mg/L and the maximum adsorption efficiency can reach 92.66%.In terms of study on adsorption mechanism, we observe the microstructure of rice husk ash before and after adsorption by means of scanning electron microscope of; use infrared spectrometer to analyze the changes of rice husk ash chemical bonds before and after adsorption to determine the chemical reaction nature of adsorption; use X-ray diffraction spectrum to judge crystal structure of rice husk ash, which reveals adsorption mechanism of rice husk ash bio-sorbent to chromium ions and mercury ions. The results showed that the component of rice husk is common cellulosic and amorphous silica; therefore, silica is the main component of rice husk ash.As suggested above, rice husk ash removes wastewater containing mercury and chromium as adsorbent, which can achieve the purpose of purifying mercury and chromium wastewater effectively. It is a wastewater treatment technology whose advantages are efficiency, no secondary pollution, and great industrial value.