Experimental Study on Shale Modified Clay as Anti-seepage Liner for Landfill

Abstract: In order to study the feasibility of shale as a clay anti-seepage high quality GCL geosynthetic clay liner modified material in the landfill, the main pollution of leachate is investigated through the adsorption test of shale particles and the penetration test of shale-modified clay material. Adsorption of NH4+, COD, and determination of the amount of crushed shale added to meet the requirements of landfill GCL geosynthetic clay liner for sale penetration. The experimental results show that the shale particles need to absorb the equilibrium of NH4+ in landfill leachate for 24h and 48h for COD. In terms of adsorption effect, when the shale particle size is above 0.075mm, it has strong adsorption capacity to COD, and the adsorption rate is between 57.57% and 61.75%, which is obviously higher than that of bentonite; the adsorption capacity to NH4+ is weaker. The adsorption rate is between 27.21% and 31.21%. When the shale addition amount is within 10%, the permeability coefficient of the shale GCL geosynthetic clay liner factory price modified clay material can reach 1×10-7cm/s or less, which meets the penetration requirements of the landfill anti-seepage liner.

Keywords: landfill; shale; anti-seepage high quality GCL geosynthetic clay liner; adsorption test; penetration test

Landfill as the final disposal technology for municipal waste is currently widely used. 90% of urban waste in China is treated with landfill technology. If the landfill is not properly protected, the resulting leachate is likely to cause local soil and groundwater contamination, so it is important to choose a good GCL geosynthetic clay liner for sale material. At present, commonly used anti-seepage materials include natural materials and synthetic materials, but the leakage of leachate generally occurs for various reasons. Therefore, it is necessary to improve the attenuation effect of the anti-seepage material on the leachate. Natural mineral materials such as clay are widely used as impermeable high quality GCL geosynthetic clay liner materials for landfills because of their good anti-seepage properties. However, due to the poor ability of natural clay to attenuate pollutants, many scholars have modified them to improve them. Its ability to attenuate pollutants.

Shale is a fine-grained layered sedimentary rock composed of silt-grade and clay-grade particles GCL geosynthetic clay liner factory price. In most parts of China, there are abundant shale reserves. Under the electron microscope, there are a lot of micropores inside the shale particles, which are nest-like (like honeycomb), so the specific gravity and bulk density are small, the body is light, and the adsorption capacity is strong. Regarding the adsorption capacity of shale, many scholars have done research in this area, and have been successfully applied to the production of ceramsite filter materials, grease and sugar liquid decolorization, water supply and wastewater treatment, but shale is used for landfill. The study of buried anti-seepage high quality GCL geosynthetic clay liner has not been seen.

In this study, shale was used to modify natural clay, and the adsorption capacity of shale particles on pollutants and the effect of crushed shale as a natural clay anti-seepage GCL geosynthetic clay liner for sale modifier on its anti-seepage ability were investigated. Therefore, how to develop shale as a barrier high quality GCL geosynthetic clay liner material has high environmental and economic benefits.

1. Experimental process

According to the adsorption capacity of shale GCL geosynthetic clay liner factory price, the adsorption of shale particles to the main pollutants of landfill leachate NH4+ and COD is explored by shale particle adsorption test. At the same time, the shale modified clay material is penetrated by smashing. The experiment was conducted to study the effect of crushed shale as a clay anti-seepage high quality GCL geosynthetic clay liner modifier on the anti-seepage ability, and to determine a reasonable additional amount of the crushed shale modifier.

1.1 Test materials
Shale, bentonite and fly ash are purchased from the market, and clay is taken from a landfill. The chemical analysis results of each material are shown in Table 1. Previously, some scholars used clay and fly ash to modify the clay. They have certain adsorption capacity for the GCL geosynthetic clay liner factory price pollutants in the landfill leachate. Therefore, they are also subjected to adsorption tests as a comparison of shale adsorption capacity.

Table 1 Composition of each material unit: %

The shale was first broken through a 2 mm analysis sieve for particle size analysis and left as an additive for the penetration test. The crushed shale is crushed by a micro-grinder and passed through 2mm, 0.5mm, 0.25mm, 0.15mm, and 0.075mm analytical sieves high quality GCL geosynthetic clay liner, and shale in different particle size ranges is taken as the adsorption test material. The clay is air-dried to remove coarse particles for particle size analysis. The particle size distribution curve of clay and broken shale is shown in Fig. 1. The plastic limit of clay is 20.66%, the liquid limit of 10mm is 31.06%, and the liquid limit of 17mm is 40.17%.

The landfill leachate was taken from a landfill. The concentrations of NH4+ and COD were 686.01 mg/L and 1653.28 mg/L, respectively.

1.2 Test instruments and reagents
Micro pulverizer; 2mm, 0.5mm, 0.25mm, 0.15mm and 0.075mm analytical sieve; 250mL conical flask GCL geosynthetic clay liner for sale; electronic balance; oscillator; 25mL, 50mL test tube; oven; UV-2450 UV-visible spectrophotometer; Combined tester; light compaction cylinder; bulldozer; wire saw; soil cutter; TST-55 type permeameter.

Potassium sodium tartrate solution; Nessler reagent GCL geosynthetic clay liner for sale; masking agent; 0.2 mol/L potassium dichromate digestion solution; Ag2SO4-H2SO4 catalyst.

Figure 1 Particle size distribution curve of clay and crushed shale

1.3 Test methods and procedures
(1) Adsorption test method and procedure: 10 g of bentonite, fly ash GCL geosynthetic clay liner factory price, clay and different particle size shale were placed in a 250 mL stoppered conical flask, and 100 mL of landfill leachate was added and placed on a shaker. Shake at 120 r/min for 24 h, 48 h, and 72 h at 20 °C. The oscillating liquids were taken at different shaking times high quality GCL geosynthetic clay liner, and after filtration, the NH4+ concentration and COD concentration were determined by Nessler’s reagent photometry and rapid closed catalytic digestion. According to the concentration change, the time, adsorption amount and adsorption rate required for each soil sample to reach the adsorption equilibrium were determined.

(2) Penetration test method and procedure: A dry clay of PN weight and a crushed shale of weight PY were taken GCL geosynthetic clay liner for sale and mixed. The samples were prepared by adding water to the water content associated with the plastic moisture content of the clay, and then the materials were stored for 24 hours and then compacted, and then sampled with a ring knife. The weight percentage of the pulverized shale is determined by B = (PN / PY) × 100%. The amount of crushed shale added to the clay is 0%, 5%, 10%, 15%, 20%, 30%, respectively. The amount of water added was 21% (slightly greater than the plastic moisture content of the clay). The size of the ring cutter is 40 mm thick and 61.8 mm in diameter. Distillation water and landfill leachate were used to conduct a comparative study on the soil samples of several different crushed shale additions high quality GCL geosynthetic clay liner. Infiltration is carried out according to the standard using a TST-55 variable head permeator.

2. Test results and analysis

2.1 Adsorption test results and analysis
The adsorption test was carried out according to the above experimental GCL geosynthetic clay liner for sale method to detect the concentration of NH4+ and COD in the oscillating liquid at different oscillation times. The data are shown in Table 2 and Table 3.

It can be seen from Table 2 that when the shaking time is 24h, the adsorption of NH4+ by various soil samples reaches equilibrium, and the concentration of NH4+ changes only slightly after 24h. Therefore GCL geosynthetic clay liner for sale, it is determined that the adsorption equilibrium time of shale particles and other soil samples on the leachate NH4+ is 24h.

It can be seen from Table 3 that when the shaking time is 48h, the adsorption of COD in the leachate is balanced by each soil sample high quality GCL geosynthetic clay liner, and the COD concentration is only slightly changed after 48h. Therefore, it is determined that the adsorption equilibrium time of shale particles and other soil samples on COD in leachate is 48h.

Table 2 Concentration of NH4+ in the oscillating fluid at different oscillation times: mg/L

Table 3 Concentration of COD in the oscillating fluid at different oscillation times: mg/L

The concentrations of NH4+ and COD in the original leachate were 686.01 mg/L and 1653.28 mg/L, respectively GCL geosynthetic clay liner for sale. After a certain period of oscillating adsorption, the concentrations of these two indicators tend to be balanced. The NH4+ and COD concentration values ​​in the oscillating liquid were shaken for 48 hours, and the adsorption amount and adsorption rate were calculated GCL geosynthetic clay liner factory price according to the formula.

Where: S is the index concentration (mg/g) adsorbed on the soil particles at equilibrium; R is the adsorption rate (%); C0 is the initial concentration of the measured index in the solution; C is the equilibrium concentration of the measured index in high quality GCL geosynthetic clay liner the solution; V is the volume of the solution; MS is the mass of the shale. The adsorption test results of NH4+ and COD in several groups of different soil samples are shown in Tables 4 and 5.

Table 4 Adsorption test results of different soil samples for NH4+

The removal of NH4+ from landfill leachate by several groups of GCL geosynthetic clay liner factory price soil samples is mainly achieved by electrostatic adsorption and ion exchange of negatively charged soil particles. It can be seen from Table 4 that for the adsorption effect of NH4+, several groups of shale with different particle size ranges are similar GCL geosynthetic clay liner for sale, and the adsorption rate is between 27.21% and 31.21%, which is lower than that of bentonite, but higher than that of fly ash and clay.

Table 5 Adsorption test results of different soil samples for COD

Several soil samples used in the experiment contained a large specific surface area. When this kind of substance acts on landfill leachate containing a large amount of organic and inorganic colloids, it acts as colloidal condensation tuberculosis. Organic compounds can be adsorbed on high quality GCL geosynthetic clay liner the surface of mineral particles due to surface adsorption energy, van der Waals forces, hydrogen bond coordination bonds, and π bonds. At the same time, agglomerated aggregate flocs have been adsorbed, and the organic colloidal particles are adsorbed by the huge surface during GCL geosynthetic clay liner for sale the movement to generate larger flocs, which makes the system lose stability and settle, which is the main mechanism of adsorption of organic matter.

Several experimental soil samples were observed under an electron microscope GCL geosynthetic clay liner factory price. As shown in Fig. 2, shale and bentonite have similar sheet-like structures. However, compared with bentonite, there is a gap between the sheet and the sheet of shale, so that there are a large number of micropores inside the shale particles, which are nest-like (like honeycomb). This microporous structure makes the shale have a strong adsorption capacity for COD. It can be seen from Table 5 that the GCL geosynthetic clay liner for sale adsorption rate of COD in shale in the range of 0.075 mm to 2 mm is between 57.57% and 61.75%, which is significantly higher than other soil samples, but when the particles are pulverized to below 0.075 mm. This microporous structure is destroyed, resulting in a decrease in its ability to adsorb COD.

Figure 2 Electron microscopy images of bentonite (top left), fly ash (top right), clay (bottom left), and shale (bottom right)

2.2 Permeability test results and analysis
The initial and final heads of different time periods are recorded, and their permeability coefficients are calculated according to the formula.

Where: a is the cross-sectional area of ​​the variable head pipe (cm2); 2.3 is the transformation high quality GCL geosynthetic clay liner factor of ln and log; L is the permeation diameter, ie the height of the sample (cm); t1, t2 are the start and end of the reading head respectively Time (s); H1, H2 are the starting and ending heads, respectively. The results of the permeation test of soil samples with different crushed GCL geosynthetic clay liner factory price shale additions are shown in Figures 3 and 4.

Figure 3: Permeability coefficient of several groups of soil samples under the infiltration of distilled water

Figure 4: Permeability coefficient of several groups of soil samples under the infiltration of landfill leachate

Since the pulverized shale contains more coarse particles GCL geosynthetic clay liner factory price, adding it to the clay will change the particle gradation of the original soil, which will increase the permeability coefficient of the soil sample. At the same time, due to the adsorption of the modified soil sample, as it adsorbs ions in the landfill leachate, the permeability coefficient of the soil sample will also increase. It can be seen from Fig. 3 and Fig. 4 that whether the permeation of distilled water or the infiltration high quality GCL geosynthetic clay liner of landfill leachate, the permeability coefficient of clay can reach below 1×10-7 cm/s, and the modified soil sample with different shale addition amount The permeability coefficient is increased to different degrees than clay. Especially for the modified soil samples with high addition amount, the permeability coefficient is obviously increased. With the penetration, the permeability coefficients of several modified soil samples tend to balance.

The permeability coefficient of the modified GCL geosynthetic clay liner factory price soil sample with 5% and 10% crushed shale addition amount can be 1×10-7cm/s or less, although it is slightly increased compared with clay.

In the case of the penetration of distilled water, the permeability coefficient of GCL geosynthetic clay liner factory price the modified soil sample with 15%, 20% and 30% crushed shale addition is difficult to reach below 1×10-7cm/s; and in the case of landfill leachate permeation, except 30 The remaining shale additions of the soil sample can be reduced to less than 1 × 10-7 cm / s. On the one hand, because the landfill leachate contains a large amount of inorganic, organic impurities, suspended solids, etc., it is blocked by the soil sample in the gap, thereby reducing the scouring effect of the water flow on the soil particles; at the same time, the landfill leachate is sticky due to charged ions. The degree is higher high quality GCL geosynthetic clay liner than that of distilled water, and the permeability coefficient decreases with the increase of viscosity so that the permeability coefficient of the soil sample decreases. On the other hand, by ion exchange or adsorption, the cation can enter the interlaminar space of the clay mineral crystal, which has an effect on the interaction between the layers. Usually, the increase of the ion concentration or potential causes the interlayer repulsive force to decrease, thereby making the soil particles Aggregation occurs; and heavy metals GCL geosynthetic clay liner for sale, carbonates, etc. in soil and landfill leachate cause flocculation and precipitation due to physical or chemical reactions, thereby reducing the permeability coefficient of soil samples.

The permeability coefficient of several groups of soil samples, when the permeability GCL geosynthetic clay liner factory price is stable, is taken to compare the influence of the amount of crushed shale added on the permeability coefficient of the modified soil sample, as shown in Fig. 5.

Fig.5 Effect of shale addition on the permeability coefficient of modified soil samples

It can be seen from Fig. 5 that whether it is the penetration of distilled water or the infiltration of landfill leachate high quality GCL geosynthetic clay liner, the permeability coefficient of the modified soil sample increases with the increase of the amount of crushed shale added. When the amount of crushed shale added is not more than 10%, the permeability coefficient of the modified soil sample can satisfy the requirement of less than 1×10-7 cm/s.

3. Conclusion

(1) Through the shale particle adsorption test and the osmosis test of shale modified clay material, it is feasible to crush shale as a landfill anti-seepage high quality GCL geosynthetic clay liner, which has both technical and economic advantages.

(2) It can be seen from the adsorption test GCL geosynthetic clay liner factory price that when the particle size of shale particles is above 0.075mm, the adsorption rate of COD is between 57.57% and 61.75%, which is significantly higher than that of bentonite and fly ash, but in the particles. When pulverized to less than 0.075 mm, the adsorption GCL geosynthetic clay liner for sale capacity for COD decreases; the adsorption rate for NH4+ is between 27.21% and 31.21%, which is lower than that of bentonite, but higher than that of fly ash and clay. The shale particles have certain adsorption capacity to the main pollutants of landfill leachate, NH4+, and COD.

(3) It can be seen from the penetration test that when the GCL geosynthetic clay liner factory price shale addition amount is less than 10%, the permeability coefficient of the modified soil sample can satisfy less than 1×10-7cm/s regardless of the use of distilled water or landfill leachate. Claim.

(4) There are many organic and inorganic pollutants in landfill leachate. NH4+ and COD are only a large amount of pollutants. The adsorption capacity of shale particles for pollutants needs further consideration; crushing shale modified clay As a landfill anti-seepage high quality GCL geosynthetic clay liner, in addition to meeting the requirements of penetration, it is necessary to consider the shear strength of the GCL geosynthetic clay liner for sale, the ability to resist cracking, etc., and further experimental research is needed.