Extraction Of Weathered Coal Humic Acid And Remediation Of Lead-Contaminated Soil

China has a large reserve of weathered coal,there are abundant weathered coal resources in north and southeast of Shanxi Province Weathered coal is one of the main sources of ore source humic acid.However,at present,the extraction efficiency of humic acid from weathered coal is very low,and the pollution consequently has been found severe.How to improve the extraction efficiency,and optimize extraction process is becoming a research hotspot.Soil heavy metal pollution has been a serious problem with the development of industrialization.The lead-contaminated soil in China has reached 3.3 million hectares,which is widely distributed and harmful.The application of weathered coal humic acid in the remediation of lead-contaminated soil has important practical significance.In this study,ultrasonic pretreatment method was used to extract humic acid from weathered coal combined with KOH solution,different KOH solution concentration,water-coal mass ratio,ultrasonic power,action temperature and time of action were applied to the extraction rate of free humic acid in weathered coal.The effect of the extraction was characterized by infrared spectroscopy.In addition,by simulating the single lead contaminated soil,combined with indoor culture and pot experiment,the lead concentration of soil and plant and soil enzyme activities were analyzed,the effect of weathered coal humic acid on lead-contaminated soil was also explored.Our results will provide a theoretical basis for the extraction and industrialization of ore source humic acid,and provide technical support for the remediation of soil lead pollution.The main results are as follows:(1)The optimum process parameters for extracting humic acid are: KOH solution with a concentration of 2%,the mass ratio of weathered coal to KOH solution is 1:8,the ultrasonic extraction power is 150 W,the extraction time is 30 min,and the reaction temperature is 45 °C.The concentration of water-soluble humic acid is 22.81%,with a extraction rate of 65.32%.(2)The results of infrared spectra showed that the absorption peak of phenol,alcohol key from weathered coal strengthened after ultrasonic treatment.The characteristic absorption peaks of phenolic hydroxyl group,the Si-O and C-H on the vibration and aromatic ring of plane bending vibration from humic acid strengthened after ultrasonic treatment with KOH extraction.This implied that the role of KOH was very important,and ultrasonic treatment had an effect of activation.(3)Humic acid is beneficial to reduce the concentration of soil available lead,with an effect of remediating lead-contaminated soil,and can effectively reduce the lead concentration of plants,the absorption of lead in soil and the toxicity of lead to plants.After adding humic acid to lead-contaminated soil,the concentration of soil available lead decreased by 16%~20%,and the lead concentration of the small rapeseed plants decreased by 60 %.(4)Humic acid can increase the activity of soil sucrase,catalase and urease.After the addition of humic acid to lead-contaminated soil,the activities of soil enzyme increased.Soil invertase activity increased first to a certain value and then tended to be a level.Soil oxidoreductase and urease increased first and then decreased.In conclusion,ultrasonic wave can increase the active functional group of humic acid,improve the activity of humic acid and its application effect.The application of humic acid from weathered coal had significantly effect on the remediation of soil lead pollution and the improvement of biological fertility.