Potassium Extraction And Recovery In Straw

Straw is a kind of common agricultural waste in rural areas, and it would reach over 800 million tons in China each year. A considerable research has been carried out in recent years, which indicated that the potassium content of straw is quite high. Supposing the potassium percentage in straw is 2%, the output of potassium will reach over 16 million tons each year. Thus, the recycling of potassium in straw comes to be of great economic and social values. Aiming to research into rice straw, based on the analysis of potassium content and forms, my paper firstly introduces the way to dissolve potassium from rice straw in microwave technology, studies the conditions of dissolution, which has explored a technological method in recycling of potassium in straw.The papers was to determine potassium in rice straw by chemical fractionation, and the result showed that the total amount of potassium in the straw was up to 3.7%, 2.7% in water-soluble potassium, 0.9% potassium in organic matter, and 0.17% potassium in hydrochloric acid matter. That is to say, the three matters of potassium in the total amount were 73%, 22% and 5% respectively.In method of mixing water soluble can strip 73% potassium (water-soluble potassium), while in microwave digestion can strip more than 90% potassium, which is significantly higher than the result in method of mixing water soluble. The result indicated that microwaves can destroy cell wall and can release potassium in organic matter. To optimize the microwave digestion, as potassium dissolution rate of indicators, to study influence of potassium dissolution rate by testing sample particle size and digestion time and microwave power and liquid to solid ratio with single factor method and orthogonal experiment method, potassium dissolution rate increased with the decrease of particle size and increase digestion time, the best potassium dissolution rate at microwave power 280W, the ratio of liquid to solid 30. Among sample particle size and liquid to solid ratio influenced potassium dissolution rate the highest (P<0.01), and microwave power influenced the lower (P=0.151), and digestion time influenced the lowest (P=0.494) by orthogonal experiment. The optimized conditions of straw by microwave digestion were as follows: sample particle size 40mesh, microwave power 280W, the ratio of liquid to solid 35 and digestion time 70s. Under these conditions, the amount of potassium to separate out accounted for 94.6% of the total potassium.Based on result of infrared and technical data, determined preliminarily in the dissolve organic matter (DOM), there may be transphilic and hydrophobic. Basified samples were extracted with ether and were measured maximum absorption band with UV detector at 213 nm. In this wavelength, content of DOM in digestion solution was determined by absorbance. D065 macro porous resin was used for adsorption and separation of DOM in K solution. Based on single-factor test, the influencing factors such as pH, temperature, concentration and velocity of eluant were studied. The optimal process route and conditions were suggested in this paper: the optimal adsorption was at room temperature and acidic medium (pH=2), velocity was 0.03mL/(min·mL resin), and the DOM was eluted by 80% ethanol at acidic medium (pH=10), velocity was 0.05mL/(min·mL resin), under these conditions, the adsorption rate of DOM was 94%, and the separation of potassium in the course of recovery was 97.5%.Ammonium form of natural zeolite was used for adsorption and separation K in digestion solution. Based on single-factor test, the influencing factors of adsorption of K as potassium concentration in the digestion solution, fulfilled height (height diameter ratio), velocity were studied. The optimal test parameters were as follows: the column of the concentration was 4.12mg/mL, height diameter ratio was 24, velocity was 0.067mL/(min·mLzeolite), K penetrating ratio was less than 10%, zeolite adsorption capacity was 16.02mg/g. Used NH₄HCO₃ as eluant liquid, the optimal extrication test parameters were 1mol/L NH₄HCO₃, velocity was 0.083mL/(min·mL zeolite), under optimum conditions, potassium analytical rate was 98.08%, in crystal products: KCl 49.38%, NH₄Cl 49.16%, NaCl 1.74%, DOM 0.72%, that shows DOM and Na⁺ were separation by ammonium form of natural zeolite.According to the experimental results and technical data, the process route was considered in my paper that by microwave digestion straw, K separation and extraction by ammonium form of natural zeolite, and residues treatment. A scientific, rational, simple and convenient way was found out for the comprehensive utilization of straw in this paper.