| The use of Sanitary landfills is a final treatment option for (municipal solid waste) MSW, and is still important in all treatment options. At present, landfill is one of primary treatment options, which is used in most countries. Sanitary landfills of the MSW can pollute the surrounding environment and the main problem is that the leachate easily pollutes the surrounding soil and groundwater. As the leachate can directly cause harm to people, the design of bottom liners is crucial to the landfill's construction.With its low price, availability and easy construction, the natural clay liner was thought of as the good liner material and was used universally in engineered landfills. However, the natural clay liner has some disadvantages; for example, dryness, freeze/thaw and contraction cracks can increase the hydraulic conductivity of the compacted clay. In addition, the clay liner is liable to attack by organic pollutants of high concentration, resulting in an increase of hydraulic conductivity, which cause accidental leakages of leachate.It is well known that, it is very difficult and expensive to remediate polluted groundwater and soil, therefore in the past years many scholars have paid attention to the remediation of these leakages. For instance, based on the electrophoresis theory, clay granules can be attracted to wall up the leakages of the clayed liner, but it has high operational costs and low efficiency. There is another method identifying the positions of the leakages and then remove the solid waste before repairing the leakages, but this method wastes time. As it is difficult to repair the leakages, new methods should be investigated to reduce the probability of leakage and the degree of the pollution. This paper designs a series of batch tests and two groups of experiment to research into new pattern double mineral base liners with long time and low permeability. First of all, because leachate is a kind of wastewater, rich in various contaminants, especially organics, bentonite was modified with Hexdecyl-trimethyl-ammonium bromide that contains hydrophobic long alkyl chains to assess the efficiency of modified bentonite in removing organics and other factors affecting the sorption.Secondly, according to the new concept of Double Mineral Base Liner,a group of experiments were designed to confirm the feasibility of the organically modified bentonite as an active layer material by contrasting the breakthrough curve and adsorption impact of organobentonite and natural bentonite. Then the permeability and attenuation effect of double mineral base liners polluted by the leachate in the second group test was investigated. In this test comparisons were made between the attenuation and permeability of different positions of the active layer and the inactive layer. At last, this paper puts forward a new type liner that can retard organic pollutants in leachate and reduce the impact of leachate on groundwater and soil. According to the experimental results, we can draw some conclusions as follows:1. batch-sorption tests⑴We import cationic surfactants(HDTMA) to modify the natural bentonite, X-ray diffraction analysis show that the inter-layer distance of organobentonite is larger than that of natural bentonite. That is to say, organobentonite has increased the capability of adsorption.⑵A series of tests done on the influence of time and pH on the adsorption of phenol by modified bentonite showed organobentonite can adsorb organic pollutants in short time, which is an advantage, if it is to be used in real liners. In addition, organobentonite can adsorb phenol better in the alkaline condition than in the acidic condition. ⑶According to the equilibrium isotherms of phenol sorption by HDTMA-modified bentonite and natural bentonite, it was observed that the main adsorption theory is adsorption mechanism ,other than partition.2. Column experiments in labIn this phase, the permeability and attenuation of the contamination in monolayer and double mineral base liners were analyzed.⑴ W... |
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