| In recent years, some wastewater containing chromium ion is discharged, and ithas become one of the important sources which bring pollution to the ecologicalenvironment，and that the chromium ion has direct or indirect harm to the health ofhuman beings. When the human body skin contact, it can cause skin allergy，and iteven can cause inherited gene defects. It is more likely to cause cancer after it isinhaled by people and it is risk to the environment. Adsorption method dealing withhexavalent chromium ion is widely adopt, which has some advantages such as simpleoperation, good adsorption performance, wide application, and can be recyclingrenewable. Currently the adsorption material of hexavalent chromium ion isnon-biodegradable petroleum base polymer resin compounds, so the development ofnew type of biodegradable specificity adsorption materials of hexavalent chromium ionis of great significance. Natural plant fiber comes from the natural plant, which isrenewable, and biodegradable. We can realize the fiber materials′directionaladsorption by controling the functional groups in the process of graft modification.Based on natural fiber′s renewable and biodegradable, this study uses the fiber′sreactive functional groups-hydroxyl groups make it realize the specific adsorption ofhexavalent chromium ion by grafting on the functional groups which have specificadsorption of hexavalent chromium ion. At the same time we discuss the fiber′spretreatment method which effect the adsorption capacity of modified fiber, anddiscuss the desorption and regeneration performance of the modified fiber.The results showed that after alkali treatment, the fiber reacts with(3-chloro-2-hydroxypropyl) trimethyl-ammonium chloride， after the reaction, weprepare cationic fiber adsorption materials. The modified fiber has a light yellow color,the content of N has obvious changes, appear the absorption peak of ether and C-Nkeys. Grafted cellulose′s crystal structure has no obvious changes, but the crystallinitydecreased, the fiber′s surface appears granular material, and the fiber′s thermal stabilityimproved.The adsorbent dosage, temperature, time, pH all have a certain degree ofinfluence on the modified fiber′s adsorption of hexavalent chromium ion. The pH valueis the main factors of affecting the adsorption performance. For the modified fiberprepared by this study, under the adsorption temperature is45℃, the adsorption time is30min, the adsorption of the pH value is3.23of the modified fiber′s adsorption onhexavalent chromium ion have the maximum adsorption capacity, the maximumadsorption capacity can reach10.8mg/g.The effect of beating degree on fiber grafting is positive impact. Improve thefiber′s beating degree, the final modification fiber′s grafting rate increased, theroughness of fiber surface increased, the crystallinity is decreased, the thermal stabilityis improved. By beating pretreatment, it improves the modified fiber′s adsorptioncapacity. After beating the modified fiber′s adsorption quantity are higher than notbeating of modified fiber in the same condition, and the beating degree is higher, thegreater effect on the modified fiber′s adsorption capacity. In this study the biggestadsorption capacity of the final modified fiber can reach15.2mg/g.The modified fibers has a good effect of desorption in50ml of5%NaOH and50ml of5%NaCl solution, and the rate of desorption can reach more than95%. Themodified fiber also has good adsorption performance after desorption, and themaximum adsorption capacity is declined slightly than the original modified fiber. Thebeating degree has a little effect on the rate of fiber desorption and the biggestadsorption amount of readsorption after desorption. |
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