Microwave And Ultrasonic Enhanced H 2 O 2 Oxidation-leaching Combined With Technical Research And Development To Repair Chromium Contaminated Sites

With the rapid development of industry and agriculture, environmental pollution is becoming increasingly serious, the soil is inevitably seriously polluted, especially heavy metal pollution to the soil,not only the public life and property security poses a direct threat, but also to economic development and society Stability brought great test. In recent years, the problem of heavy metal chromium pollution has become more prominent,the pollutants in the soil with a long time to stay,strong concealment,toxicity and other characteristics, and through the food chain directly or indirectly harm people's health and even life, therefore, for chromium pollution sites Of the restoration of work without delay.In this paper, the soil of chromium pollution field in a chemical plant site in Jinan City is taken as the research object. Some of the previous research results,innovative methods and improved techniques are put forward. The physical strengthening and oxidation-leaching combined repair technology is put forward. The main form is supplemented by microwave or ultrasonic enhanced H₂O₂ oxidation capacity, and combined with chemical leaching of chromium pollution sites for repair.In this paper,the basic physical and chemical properties of four sites contaminated by chromium in this region were analyzed. Then,single factor experiment protocol and orthogonal design were designed for microwave enhanced H₂O₂ oxidation-leaching combined repair technique and ultrasonic enhanced H₂O₂ oxidation-leaching combined repair technique. The effects of two factors ?oxidant concentration,ultrasonic time, soil-to-liquid ratio, pH, microwave time, microwave power? on the removal rate of total chromium in four sites were studied. Finally, the effects of each of the two sites The best governance plan for the practical application of engineering data reference, the main conclusions are as follows:?1? Through the analysis of soil physical and chemical properties of four chromium contaminated sites, it was found that the chromium content in the soil of four sites was seriously higher than the standard of residential land in the secondary standard of soil quality ?Cr ? 400mg · kg-1? Single factor index Pi value of 16.66-24.26, are heavily polluted. The chromium content in the soil of chromium salt production workshop is 8072.75 mg · kg-1, the chromium content in the soil is 7283.75 mg · kg-1, the content of chromium in the soil is 9703.33 mg · kg-1 And the content of chromium in the soil of the northern plant was 6665.87 mg · kg-1. And the content of hexavalent chromium in the four sites is different. The content of hexavalent chromium in the chromium salt production workshop is 19.43 mg · kg-1,and the content of hexavalent chromium in the soil is 3.92 mg · kg -1, the content of hexavalent chromium in the soil was 709.69 mg · kg-1? and the content of hexavalent chromium in the soil was 449.51 mg · kg-1 in the northern part of the plant. It was found that the chromium pollutants in the first two sites The migration activity is very low, and it is mainly in the form of trivalent chromium in the soil. The migration activity of chromium pollutants in the two sites is relatively high and the damage is large,but the proportion of total chromium in the soil is only a small proportion.?2? The results of single factor experiments showed that the removal rate, cost and safety of the two oxidants were 3% when the concentration of oxidant was 3% in different oxidant concentration. The removal rate of total chromium was 2.74%,2.96%, 12.85% and 14.58%, respectively. At the optimum oxidant concentration, the removal rate was better when the ratio of soil to liquid was 1: 2, and the total chromium removal rate Respectively. The total chromium removal rate of the four sites was 4.70%, 2.98% and 2.98% respectively, and the total chromium removal rate was 4.70%, 2.98% and 2.98% respectively. Under the optimum conditions, %,21.20% and 19.94%, respectively. The change trend of total chromium removal rate in four sites was different from that in pH, and the chromium salt production workshop and 10,000 tons of chromium salt production workshop were at pH = 10 The total chromium removal rate was ideal, the total chromium removal rate was 9.76%, 6.73%.While the removal rate of total chromium was better at pH = 6, which was 42.85%and 56.58%, respectively.?3? Orthogonal optimization experiment of H₂O₂ oxidation-rinse combined with repair technology showed that the optimal solution of chromium salt production workshop was 3% for oxidant, 1: 2 for soil and water, 10 min for ultrasonic, pH 8, the removal rate of 12.44%, the cost of 0.11 yuan; million tons of chromium salt production workshop for the best repair solution for the oxidant concentration of 3%,soil to liquid ratio of 1: 3, ultrasonic time of 15 min, pH 10, The ratio of soil to liquid is 1: 2, the ultrasonic time is 5 min,the pH is 6, the removal rate is 61.45%,the cost is 6%, the cost is 0.14 The optimum remediation scheme was: the concentration of oxidant was 3%, the ratio of soil to liquid was 1: 2, the ultrasonic time was 10 min,pH was 8, the removal rate was 49.35% and the cost was 0.11 yuan.?4? Microwave enhanced H₂O₂ oxidation-leaching combined repair technology single factor experimental results show that: microwave links, to explore the impact of different concentrations of oxidants found that four sites (chromium salt production workshop, 10,000 tons of chromium salt production workshop, The removal rate of total chromium was 8.97%, 13.29% and 54.7%, respectively, and the removal rate of total chromium was 8.97%, 13.29% and 54.7%, respectively. The removal rate of total chromium was 8% And 62.46%, respectively. The removal rate of total chromium was 15.70%, 15.20%, 62.22% and 62.53 respectively when the ratio of soil to liquid was 1:3. The removal rate of total chromium was 16.74%, 16.24%, 65.52% and 67.76%respectively. The results showed that the microwave removal rate was 60.7% The removal rate of the total chromium was 17.06%, 16.13%, 75.55% and 76.47%,respectively, when the irradiation time was about 10 min. PH of the total chromium removal rate of the larger, of which chromium salt production workshop and tons of chromium salt production workshop two sites the best pH is selected 9, the total chromium removal rate was 65.57%, 51.68%; and East chromium The optimum pH of the slag and the northern plant was 7, and the total chromium removal rates were 89.40% and 84.03% respectively.?5? Microwave enhanced H₂O₂ oxidation-leaching combined repair technology Orthogonal optimization experiment results show that: the best solution of chromium salt production workshop is: oxidant concentration of 9%, soil to liquid ratio of 1: 4,microwave power of 600 W,Microwave irradiation time of 10 min,pH 9, the removal rate of 60.79%, the cost of 0.23 yuan; million tons of chromium salt production workshop the best repair program: oxidant concentration of 9%, soil to liquid ratio of 1: 4, microwave The microwave treatment time is 10 min, the pH is 9, the removal rate is 53.66% and the cost is 0.23 yuan. The best remediation scheme of the East chrome slag is: the oxidant concentration is 7%, the ratio of soil to water is 1: 4, the microwave power is 800 W,the microwave irradiation time is 10 min,the pH is 7, the removal rate is 89.77% and the cost is 0.22 yuan. The best repair scheme in the northern area is 7% oxidant concentration, : 4,microwave power of 800 W,microwave irradiation time of 10 min,pH 7, the removal rate of 83.53%,the cost of 0.22 yuan.Based on the actual situation and comprehensive consideration, from the treatment cost and the total chromium removal rate as well as the single factor experiment, the orthogonal experiment results are analyzed in many ways, and then according to the physical and chemical properties of different sites and the degree of pollution, The best repair program for the site.