تأثیر کامپوزیت‌های دوگانه و سه‌گانه تهیه شده از زئولیت-کیتوزان-بیوچار بر برخی ویژگی‌های مکانیکی خاک

Abstract
Background and Objectives: So far many methods have been used to improve the quality of the soil dynamic, depending on the desired goal, (whether it is for crop cultivation and amendment of arable and agricultural soils, or in terms of construction and increasing soil stability). One of the methods is use of zeolite, chitosan and biochar modifiers separately. Biochar is the carbon-rich that can have a favorable effect on the mechanical properties of the soil and increases soil stability. Zeolite is used as a physical soil modifier to increase Soil stability, ventilation and improve the structure of sandy and clay soils and Chitosan, which is the most abundant biological polymer, It has the potential to increase increase the interaction between soil particles and improves the soil mechanical properties. Soils that are not suitable in terms of mechanical properties have low water infiltration rate, plant accessible moisture and low soil structure stability. So far, there have been no studies on the effect of the zeolite, chitosan and biochar composites on the soil dynamic properties. The purpose of this research is to investigate the effect of double and triple composites on some soil dynamic properties such as coefficient of linear extensibility (COLE), liquid limit (LL), plastic limit (PL) moistures and plasticity index (PL).
Materials and Methods: This research was conducted with randomized completely design with two factors, soil type and composite type in three replicates. In this research double and triple composites were produced from zeolite, chitosan and rice husk biochar. Dual composites include zeolite-chitosan (ZC), zeolite-biochar (ZB), chitosan-biochar (CB) and triple composites include zeolite-chitosan-biochar (ZBC). Double composites ZC, CB and triple composite ZBC were synthesized using magnetic stirrer and acetic acid (5%), half molar sodium hydroxide and double composite ZB with ultrasonication and were prepared on a laboratory scale. The treatment period was incubated for 3 months with field capacity moisture content of 65%. The mean comparison of the treatments was done with the least significant difference (LSD) test at the 5% probability level.
Results: The results showed that the type of composites had a significant effect on the liquid limit, coefficient of linear extensibility, and plasticity index of the soil. The greatest effect was related to the ZBC triple composite. This composite increased the liquid limit by 42.8% compared to the control soil and caused a 58.8% decrease in the coefficient of linear extensibility compared to the control soil. It was also observed that the plasticity index of the soil decreased with the use of composites compared to the control soil, and its effect was greater in the ZBC composite both study soil (48.5-60%) than other composites.
Conclusion: This research showed that double and triple composites can be used as suitable modifiers to improved mechanical quality of the soil. Because with the increase of the liquid limit, moisture absorption and water retention in the soil increases. Also, increasing the coefficient of linear extensibility prevents the cracking of the soil. Also, the soil that has a lower plasticity index is less soil wasted. Therefore, Therefore, based on the Results of this research, ZBC triple composite is recommended as the most effective combination for improving the physical and mechanical quality due to the increase in the liquid limit, decrease in the coefficient of linear extensibility of the soil, as well as the effect on the reduction of the plastic limit of both soil texture.it is also suggested to carry out additional studies using different levels of composites and comparing their effects on the mechanical properties of the soil.