Abstract
Thallium (Tl) is highly toxic in the environment. In order to solve the harm of Tl pollution to the environment, thiol-polystyrene microsphere (TPM) with good adsorption properties for Tl were prepared in this paper. The GAUSSIAN software was used to calculate the adsorption performance of the TPM on Tl+, and the adsorption mechanism was discussed. The thermogravimetric analysis show that the TPM prepared with chloromethyl polystyrene microspheres (CPM) and thiourea as the main raw materials has good chemical thermal stability. In the Tl+ solution of 1mg/L, the adsorption and removal rate of the TPMs in was 99%, with a significant adsorption of Tl+ properties. When the dosage of TPM is 0.4L/g, pH is 6-10, temperature is 5-20 °C, and adsorption time reaches 640min, thallium-containing water with Tl+ concentration of 5mg/L can be treated to within the national discharge standard (5μg/L). The analytical effect of 0.5mol/L dilute sulfuric acid on TPM can reach 99.96%, and the adsorption capacity of TPM on Tl+ is reduced by only 0.1% after repeated use 4 times, which has good regeneration performance. The modified polystyrene microspheres were characterized by EDS, FT-IR, Raman spectra and XPS, and it was proved that the TPM were ligated with Tl+ through the grafted mercapto group, so as to adsorb and remove Tl+ from the solution. According to the isotherm and kinetic model of TPM adsorption Tl+, the maximum saturated adsorption amount of TPM to Tl+ can reach 3.47mg/g, mainly chemical adsorption, and the membrane diffusion stage is the main control step of TPM adsorption Tl+. The results showed that the TPM could be a promising adsorbent with good adsorption capacity and reusability for Tl+ removal from wastewater
Highlights
In the natural environment, the Tl exists mainly in various sulfides ore, chalcopyrite, pyrite, silicate and other minerals[1]
The analytical effect of 0.5mol/L dilute sulfuric acid on thiol-polystyrene microsphere (TPM) can reach 99.96%, and the adsorption capacity of TPM on Tl+ is reduced by only 0.1% after repeated use 4 times, which has good regeneration performance
The chloromethyl polystyrene microspheres (CPM) before modification have basically no adsorption capacity for Tl+, indicating that the chemical groups and physical structures existing in them do not have any effect on the adsorption; Adsorption removal rate of modified tpm for Tl + increased from 5% to 99.9%, indicating that the modified polystyrene microspheres had a significant adsorption effect on Tl+, and the adsorption effect was mainly caused by the supported thiol groups
Summary
The Tl exists mainly in various sulfides (such as silver, antimony, arsenic and other sulfides) ore, chalcopyrite, pyrite, silicate and other minerals[1]. Tl is highly toxic and its toxicity to mammals is higher than arsenic, lead, mercury, copper and zinc[2,3,4]. It has serious health effects on humans by the food chain[5]. Tl poisoning can cause damage or change of nerve cells and mitochondria in animals, which can cause gastroenteritis, multiple neuropathy and hair loss, and even can pose a threat to human life under high dose intake[6, 7]. The World Health Organization defined Tl poisoning when the concentration of Tl in human urine is at the range of 4.5-6μg/L8, and the minimum lethal dose to the human is at the range of 10-15 mg/kg[9]. Treatment methods for thallium-containing wastewater include oxidation-flocculation[10, 11], chemical precipitation[12], solvent extraction[13, 14], ion exchange 15, 16, adsorption[17,18,19,20] and some composite methods based on the above ways
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