The Removal Of Haloacetic Acides In Water By Activated Carbon Fiber

Activated Carbon Fiber (ACF) is one kind of the new effective adsorbents. It hasstrong adsorption ability for all kinds of inorganic matters and organic gases, organicsubstances and heavy metals in water solutions, and its adsorption velocity is veryfast. ACF's regeneration is also very convenient. Chlorine disinfection is widely usedas a main method to ensure drinking water safety. But the generation of disinfectionby-products (DBPs) would increase the carcinogenic risk of drinking water. Theconcentration of haloacetic acids (HAAs) is a prior indicator of the total carcinogenicrisk of DBPs. Concerned removing haloacetic acids from drinking water, the thesisstudied the adsorption characteristics of HAAs onto ACF in water.This paper studied the adsorption theory and effect of ACF in water solutions, byadopting the DCAA and TCAA as the adsorbates, which only exist in water at ppblevel. The thesis concentrated on study of adsorption kinetics, adsorption models, andinfluences of adsorption conditions, such as pH, initial concentration and interferingsubstances. Meanwhile, this paper had also paid attention to ACF modification and itseffect on the experiment results, as well as ACF regeneration. Based on large quantityof experiment data, the thesis also gave an explanation to the experiment phenomena.The static experiment results showed that the amendatory Freundlich equationmatched the adsorption isotherm of HAAs on ACF best. The adsorption quantity ofACF was promoted with the increase of its specific surface, but the adsorption abilitywas not correlated with the quantity of its oxygen-containing groups. The adsorptioncapability of ACF was much better than that of GAC, and ACF could adsorb moreTCAA than DCAA. The influences of initial concentration, pH and interferingsubstances on ACF adsorption were different. The dynamic experiments showed thatthe velocity has influenced penetration time and saturation adsorption quantity. Whenvelocity V equaled to 18ml/min, the penetration adsorption quantity and saturationadsorption quantity of DCAA reached their maximums, 353.4μg/g and 466.1μg/g,respectively. The interfering substances had influence on penetration time, penetrationadsorption quantity and saturation adsorption quantity. When multi-matter existed in solutions, the penetration time moved forward and the DCAA/TCAA penetrationadsorption quantity decreased by 50% and 35%, respectively.The ACF modification experiment showed that the saturation adsorptionquantity of ACF modified by loading-microwave was the largest, and the adsorptionquantity of ACF modified by HNO₃, NaOH, and microwave were less than that ofunmodified ACE This stated that ACF modified by any of the four methodsmentioned above was not good at removing DCAA and TCAA from water. Theoptimum reaction conditions of ACF modified by loading-microwave were:microwave power 250W and the ratio of Fe³⁺ to Fe²⁺ 3 to 2. Under this situation, theadsorption quantity of modified ACF for DCAA and TCAA increased by 22.0% and6.2%, respectively.The regeneration of ACF showed that there was clear coke phenomenon ofDCAA and TCAA in microwave regeneration, and the coke phenomenon of TCAAwas more obvious than DCAA. When NaOH regeneration was employed, theregeneration of TCAA more difficult than that of DCAA. And the most suitableconcentration of NaOH solution was 1% for regeneration purpose. The dynamicexperiments showed that the adsorption quantity of regenerated ACF by NaOHdecreased apparently, and the regeneration efficiencies of DCAA and TCAA wereonly 21.6% and 46%, respectively.