RESUMO
Soil is commonly polluted by chromium, and layered double hydroxides (LDHs) are widely used for chromium removal due to their strong adsorption capacity and the unique properties of their delaminated products. In this study, delaminated LDHs (S-Mg-LDH and S-Ca-LDH) and their original LDHs were used to remediate Cr(VI)-contaminated soil. A series of characterizations confirmed the successful synthesis of delaminated LDHs whose sheet structure was thinner with a greater surface energy than the original LDHs. The remediation results indicated that delaminated LDHs could more efficiently immobilize Cr(VI) in soil. The immobilization rate of S-Mg-LDH was 64.32%, while Mg-LDH was only 8.09%. However, at low dosages, the efficiency of S-Ca-LDH was 28.1% while Ca-LDH was 5.16%, but they had similar effects at high doses. Moreover, soil pH had little effect on their removal efficiencies. The toxicity characteristic leaching procedure (TCLP) results showed that the leaching of Cr(VI) in soil after treatment with S-Mg-LDH, S-Ca-LDH, Mg-LDH, and Ca-LDH was reduced by 75.43%, 72.43%, 86.55%, and 75.90%, respectively. The phytotoxicity tests of soil treated by S-Mg-LDH and S-Ca-LDH revealed that they effectively reduced the toxicity of chromium and lowered its bioaccumulation. Overall, this study confirms the feasibility of delaminated LDHs for Cr(VI) immobilization in soils.
Assuntos
Cromo/análise , Recuperação e Remediação Ambiental/métodos , Poluentes do Solo/análise , Adsorção , Poluição Ambiental , Hidróxidos/química , Solo/químicaRESUMO
In order to guarantee that digital electrocardiographs with an adequate accuracy and reliabity are available for measurements in clinical practice, it is very important to determine the metrological characteristics, methods and to develop the equipments for verification. This paper elaborates the basic functions, specification, schematic drawing and key techniques of calibration equipments as well as test items for digital electrocardiographs.
