LI Wenbin1, ZHU Lang1, DENG Hongyan1, ZHANG Yifang1, XIE Jia1, CHEN Xinyi1, Li Ting1, MENG Zhaofu2
(1. College of Environmental Science and engineering, China West Normal University, Nanchong Sichuan 637009, China;
2. College of Natural Resources and Environment, Northwest A&F University, Yangling Shaanxi 712100, China)
Abstract: In order to explore the effects of biochar addition on the adsorption mechanisms of copper by riverbank soils, the surface (S, 0~20 cm) and subsurface (D, 20~40 cm) layers in Cangxi (CX), Nanbu (NB), Jialing (JL) and Hechuan (HC) along the Jialing River (Sichuan-Chongqing section) were collected as the target soil samples. Biochar (B) was added into the soil samples with a mass ratio of 1% to form eight mixed samples (CXSB, NBSB, JLSB and HCSB; CXDB, NBDB, JLDB and HCDB), and the original soil samples were used as the controls. Cu2+ adsorption and thermodynamic characteristics of each tested sample under different temperature, pH value and ionic strength were studied using the batch method, and the adsorption morphology of Cu was analyzed. The results showed that: (1) The Langmuir model could describe the isothermal adsorptions of Cu2+ on all tested samples well. The maximum adsorption capacity qm of Cu2+ was between 62.20 - 363.64 mmol/kg, and the adsorption amount of Cu2+ presented a trend of JL > NB > CX > HC for S layer samples and a trend of JL > CX > NB > HC for D layer samples. The application of biochar enhanced the Cu2+ adsorption on the D layer soils. (2) In the temperature range of 20~40 °C, the adsorption amount of Cu2+ increased as temperature increasing, showing the positive temperature effect. The results of thermodynamic parameters showed that the adsorption of Cu2+ by mixed samples was a spontaneous, endothermic and entropy-adding process. (3) Increasing pH was beneficial to the Cu2+ adsorption by all samples. With the increase of ionic strength, the adsorption amounts of Cu2+ in all mixed soil samples (except HCS and HCD) increased firstly and then decreased, and presented the largest at 0.1 mol/L. (4) Adsorbed copper mainly existed in carbonate-bound and iron-manganese oxide-bound states in soil samples. The application of biochar improved the exchangeable state (except HC) and the organic bound copper contents but had little effect on the carbonate bound and iron-manganese oxide bound copper contents in soil samples. The maximum adsorption capacity of Cu2+ on soil samples correlated highly with CEC and specific surface area of soil samples.
Key words: biochar; Jialing River; coastal soil; adsorption amount; copper form
EARTH AND ENVIRONMENT Vol.48, No.2, Tot No.334, 2020, Page 250-257
