Saturated permeability behavior of biochar-amended clay
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SOILS, SEC 2 • GLOBAL CHANGE, ENVIRON RISK ASSESS, SUSTAINABLE LAND USE • RESEARCH ARTICLE
Saturated permeability behavior of biochar-amended clay Wen-Jing Sun 1,2 & Ming-Yu Li 1 & Wen-Jie Zhang 1
&
Yun-Zhi Tan 2,3
Received: 7 February 2020 / Accepted: 9 July 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Purpose Biochar has the characteristics of loose porosity, high specific surface area, and strong adsorption properties. Recently, the compacted biochar amended clay has been proposed as a sustainable alternative material for the final cover of landfills. However, the effect of biochar on saturated hydraulic conductivity (ksat) is not yet conclusive. The objective of this study was to determine the influence of biochar content on the permeability of biochar-clay mixed soils. Materials and methods The clay used in the study belongs to the low liquid limit clay. The biochar is produced by heating the rice straw under an oxygen-deficient condition at a temperature of 500 °C. To study the effect of biochar content on the permeability of biochar-clay mixed soils, the biochar-clay mixed soils with the mass percentage of biochar being 0%, 5%, 10%, 15%, and 20% were used. The saturated hydraulic conductivity of the biochar-clay mixed soils was measured by the head pressure control permeameter. Meanwhile, the micro-pore structure of the saturated biochar-clay mixed soils was obtained by the nuclear magnetic resonance (NMR) technique. Results and discussion It can be observed that the saturated hydraulic conductivity ksat of biochar-clay mixed soils increases linearly as the biochar content increases. The NMR results show that the T2 distribution curve of pure clay is a unimodal pattern, while the T2 distribution curve of biochar-clay mixed soils presents the bimodal pattern, where T2 is the transverse relaxation time, reflecting the pore size of the soil specimens. With the increase of biochar content, the T2 spectrum of the mixed soils moves slightly to the right, and T2 at main peak increases gradually, correspondingly the most probable pore size of biochar-clay mixed soils increases. Conclusions The pore size distribution of the soil was changed by the addition of biochar and subsequently affects the permeability of biochar-clay mixed soils. This study provides some useful suggestions for optimizing the pore structure of the biochar amended clay anti-seepage layer in the final cover of landfills. Keywords Biochar-claymixed soils . Saturatedhydraulic conductivity . Nuclear magneticresonance . Micro-porestructure . Most probable pore size
1 Introduction Responsible editor: Hailong Wang * Wen-Jie Zhang [email protected] 1
Department of Civil Engineering, School of Mechanics and Engineering Science, Shanghai University, Shanghai 200444, People’s Republic of China
2
Hubei Key Laboratory of Disaster Prevention and Mitigation (China Three Gorges University), Yichang 443002, People’s Republic of China
3
College of Civil Engineering & Architecture, China Three Gorges University, Yichan
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