Yu Shuang Li

Remediation of Cadmium Contamination in Soil by Washing

Soil washing is a possible remediation technique for contaminant extracting from the soil. Thiacalix[4]arenetetrasulfonate has become an alternative to metal extractants due to its high selectivity and high stability. Batch soil-washing experiments were conducted to investigate the effect of pH on extraction efficiency of Cd from soil by the thiacalix[4]arenete-trasulfonate solution. Results showed that more than 82 percent of cadmium was extracted by the thiacalix[4]arenetetra- sulfonate solution from the artificially contaminated soil with the concentration of 562 mg/kg cadmium at the initial pH value of 11. Thiacalix[4]arenetetrasulfonate could be an attractive alternative in washing remediation of soil contaminated by Cd.

Effect of Mushroom Residue Used in Washed Soil on the Growth of Tomatoes

In order to reveal the regulating capacity of mushroom residue on washed soil, pots experiments were carried out. The growth of tomatoes planted on washed soil amended by mushroom residue were measured. Mushroom residue can be helpful to improve the plant height, stem diameter, the aerial parts fresh weight, root fresh weight, leaf photosynthetic rates and photosynthesis, and lay a good foundation for the growth of tomatoes. The effect of mushroom residue is the most significant. Among all the treatments of adding 2.5%, 5%, 10% mushroom residue, adding 10% mushroom residue is the best. It can significantly enhance the growth and photosynthesis of tomatoes, and is among the best of these three soil treatments for washed soil.

Composting Study of Petroleum Contaminated Soil

Composting has been shown to be an effective bioremediation technique for the treatment of hydrocarbon-contaminated soil. In this research, the major objective of this research was to find the appropriate mix ratio of organic amendments for enhancing the degradation of petroleum hydrocarbons during diesel oil contaminated soil composting. The spent mushroom was added as an amendment for supplementing organic matter for composting of contaminated soil. The volumn ratios of contaminated soil to organic amendments were 1:1, 1.5:1 and 2:1. Target contaminant of this research was diesel oil, which was spiked at 16240 mg/kg sample on a dry weight basis. The degradation of diesel oil was significantly enhanced by the addition of these organic amendments relative to straight soil control. Degradation rates of total petroleum hydrocarbons (TPH) were the greatest at the ratio of 1:1 of contaminated soil to organic amendments on the volumn ratio. The abiotic loss of TPH was only about 6.83% of initial TPH.

Cadmium Migration and Distribution Process

The significant pollution accidents which not only threaten public health and public property safety, but also bring major disaster, have become the world concerning environmental problems. The migration process and feature of CdCl2 in the vertical and horizontal profiles of soil were studied by the stimulating experiment to present the theory for the treatment of significant pollution accident. The column leaching device was taken to simulate the vertical and horizontal migration of CdCl2 in the soil profile under two-phase rainfall during 16 days. The portable manual control negative pressure pump was taken to extract soil solution sample and the CdCl2 concentration was determined by the atomic absorption spectrophotometer. Results showed that during the whole experiment, the obvious horizontal and vertical migration features of CdCl2 appeared. The CdCl2 covered the whole horizontal profile in 0.5 h and the whole vertical profile in 146 hours. The relative variation rate of CdCl2 in the different depth of bulk showed that the rapid passing time differed in the different depths. The simulating device used in this paper could well investigate the vertical and horizontal distribution and migration of contaminant. Under the condition of greater rainfall, the CdCl2 gave priority to the horizontal runoff in the surface soil, followed by the vertical migration.

Simulated Study on the Migration of Petroleum Hydrocarbons in the Soil

Spills and leaks of petroleum hydrocarbons such as gasoline, diesel, motor oils, and similar materials have caused widespread contamination in the environment. The migration and distribution of petroleum hydrocarbons in the vertical and horizontal profiles of soil were studied by the stimulating experiment. Results showed that the soil pollutions could diffuse in vertical and horizontal directions after petroleum hydrocarbons leaks. The petroleum hydrocarbons mainly spread vertically in the soil and the horizontally migration was relatively slowly. The migration distances were increased with a logarithmic growth dependence on the time both in horizontal and in vertical direction.

Desorption of Cadmium from Soils Enchanced by Citric Acid

Cadmium contamination of soil has become a major environmental problem in the whole world. Soil washing is a possible remediation method for extracting contaminants from the contaminated soil. Natural organic acids seem to be promising environmentally friendly for removing toxic metals from soils. Batch soil-washing experiments were conducted to investigate the behavior of cadmium desorption from soils by citric acid. Results showed that cadmium removal by citric acid was highly dependent on the initial pH and the concentration of citric acid. The removal of cadmium declined sharply with the rise of pH. Contrarily, cadmium desorption increased with increasing citric acid concentration. More than 90% cadmium was extracted from soil by 80 mmol L-1 citric acid.

The Preparation of TCAS-Loaded Resin and its Adsorption Property to Pb2+ Ion

A adsorbent for cadmium has been prepared by loading an anion-exchange resin with a novel supramolecular compound named thiacalix[4]arenetetrasulfonate (TCAS). The adsorption properties of Pb2+ on TCAS-loaded resin had been studied and the effects of varying temperature, pH value, adsorption time and initial concentration. Batch extraction studies had revealed a high adsorption ability of the TCAS-loaded resin toward this heavy metal ion with high selectivity. The maximum adsorption capacity of the TCAS-loaded resin toward Pb2+ was 26.32 mg•g-1. The removal rate of Pb2+ in water was up to 99% after 40min at 20°C when a 50mL aqueous solution of Pb2+ (10 mg•L-1) was adsorbed by 0.5g TCAS-loaded resin. The removal percentage steadily retained above 99% when the pH values were in the range of 4 to 7. The adsorption isotherm of the TCAS-loaded resin to Pb2+ ions fits well to linear form of Langmuir sorption equation.