Research On Rice Husk And Wheat Bran And Their Modified Materials For Cadmium Polluted Wastewater Treatment

Researching on agriculture and forestry wastes reuse, this paper obtained biological adsorbents with high adsorption capacity though modified rice husk and wheat bran by sodium hydroxide, potassium permanganate and joint on the modification. This thesis systematicly studied the influence of the adsorbent dosage, initial concentration of solution, initial pH, contact reaction time, coexisting ions and temperature on adsorption effect through the single factor of static and dynamic adsorption experiment; optimized the modified process of sodium hydroxide concentration, modification time, concentration of potassium permanganate, potassium permanganate modification solid-liquid ratio; used Characterization methods such as scanning electron microscope (SEM) and infrared spectrum characterization (FTIR) making preliminary discussion on modifcation and adsorption mechanism combining the kinetics and adsorption isotherm analysis.(1) Static adsorption of single factor experiments showed that the adsorption capacity is small when the initial pH belowing 2; rapidly increaseed within the pH into the scope of 2-4; and less changed when pH at 4 to 8. All kinds of adsorption materials reached adsorption equilibrium within 4 h. Adsorption performance of all adsorption materials influenced by coexisting ions Na+ and Ca2+ in the solution, the impact of Ca2+ was greater than Na+. It is conducive to the adsorption rising the temperature. The results factors affecting the dynamic adsorption were similar to the static adsorption experiments.(2) If the initial concentration of Cadmium solution was 50-200 mg/1, the initial pH was controlled about 6.5, the temperature was 25℃, setted the speed as 130 r/min, and oscillated for 4 hours, the maximum adsorption capacity of the materials as follows:Rice husk modified combining sodium hydroxide and potassium permanganate (28.33mg/g)> Rice husk modified by potassium permanganate (19.01 mg/g)> Rice husk modified by sodium hydroxide (12.06 mg/g)> raw rice husk (4.88 mg/g); Wheat bran modified by Sodium hydroxide and potassium permanganate (26.74 mg/g)> Wheat bran modified by potassium permanganate (21.88 mg/g)> Wheat bran modified by sodium hydroxide (7.29mg/g)> Original wheat bran (3.18 mg/g), which fully explained the effects were good of the modified materials using sodium hydroxide, potassium permanganate or combining modification or sodium hydroxide and potassium permanganate for rice husk and wheat bran, because their adsorption performance were respectively soared.(3) Though single factor experiments, it was concluded that integrated the optimal modification conditions for sodium hydroxide solution concentration control in 0.5 mol/1; Potassium permanganate solution quality concentration control in 2 w%; keeping 24 h for sodium hydroxide soaking modification at room temperature,4 h for potassium permanganate soaking modification at room temperature; and the reasonable solid-liquid ratio was 1:15 for potassium permanganate modification. The adsorption capacity in the solution were as high as 71.50 mg/g and 71.50 mg/g for potassium permanganate modified rice husk and wheat bran which was aready modified by sodium hydroxide when solid-liquid ratio of 1:50 and the initial concentration of cadmium solution was 200 mg/1.(4) The scanning electron microscopy (SEM) and infrared spectrum (FTIR) analysis showed that the structure of modified rice husk and wheat bran became more porous, increased specific surface area, wall surface becomes more coarse, exposing more functional groups, and increased some small holes and granular MnO2 substance. It was demonstrated that the process of adsorption included electrostatic adsorption and precipitation mechanism because some floc appeared on material surface after the adsorption. Infrared spectrum analysis showed that tere was no new peak appeared, but some peaks was really strengthened after modification of the rice husk and wheat bran. It made solid-liquid separation easier through the modification of rice husk and wheat bran materials at the end of the adsorption which only standing for 2 min to sink to the bottom of the solution, namely very solution to realize easily found in the process of experiment.Rice husk and wheat bran had good adsorption performance for heavy metals adsorption after simple modification, they had the advantages of low cost and easy operation. The materials showed quick absorption rates, large amount of adsorption capacity etc. This research provided a certain theoretical basis and technical guidance for heavy metal wastewater treatment using rice husk and wheat bran and their modified materials, and provided a new utilized pathway on agriculture and forestry wastes such as rice husk and wheat bran.