| Heavy metal pollution in soil is widespread.Remediating contaminated soil efficiently and safely is an urgent environmental problem faced by human beings.Plant biomimetic remediation technology based on transpiration principle has the advantages of strong in-situ applicability,low costs,and the ability to treat high concentration contaminated soil.It is a new remediation technology for heavy metal contaminated soil,showing a broad prospect.In this dissertation,ordered porous ceramics were prepared by freeze-drying method and solid-phase sintering method.The effects of temperature gradient,solid content,composition and proportion of dispersion medium on ordered pore structure were discussed.The ordered pore structure was characterized by SEM,CT and mercury injection.Meanwhile,the optimal transpiration materials were used to simulate plant leaf.The imbibition performance of ordered porous ceramics and transpiration performance of transpiration materials were studied.Furthermore,the remediation of Cr（Ⅵ）and Cu（Ⅱ）contaminated soil were explored.The main conclusions were as follows:（1）Ceramic samples with different solid content prepared by bacterial cellulose hydrogel all have directional and ordered pore structures.The diameter of one-way pore decreases with the increase of solid content,and the pore size of single pore increases with the decrease of temperature gradient,and the larger size pore appears on the top of ceramic samples.The pore structure of dried green body and ceramic sample is optimized by the introduction of tert-butyl alcohol.The pore structure at the top of dried green body prepared by the mixed dispersion medium containing 3 wt%tert-butyl alcohol is uniformly distributed,and the appearance of large pore is avoided.In the sintered ordered porous ceramics,a vertical directional channel like xylem is formed from bottom to top,and there are micropores on the pore wall that can transport water laterally.（2）Ordered porous ceramics with low solid content have a larger imbibition rate at the initial stage of imbibition,indicating that larger pore size corresponds to a greater imbibition rate.With the increase of imbibition height,the top of sample optimized by adding 3 wt%tert-butanol is narrow and orderly,and is more conducive to the transportation of water to a higher position.The order of transpiration rate of three transpiration materials is as follows:bamboo pulp fiber paper>wood pulp fiber paper>cotton yarn.The transpiration rate of bamboo pulp fiber paper can reach 165.21 g·h-1·m-2.（3）The bionic remediation material composed of ordered porous ceramic and bamboo pulp fiber paper is more favorable to remove the anion groups weakened by the electrostatic action of soil colloid.The seven times removal rates of Cr（Ⅵ）and Cu（Ⅱ）reach 98.61%and36.89%,respectively.The remediation property of bionic remediation material has improved with introducing N,N-bis（carboxymethyl）-L-glutamate tetrasodium（GLDA）.When the ratio of GLDA:Cu（Ⅱ）is 5:1,the seven times removal rate of Cu（Ⅱ）increases to 58.48%.Ultrasonic-GLDA combined pretreatment is further used.When the ratio of GLDA:Cu（Ⅱ）is3:1 and ultrasonic time is 15 min,the seven times removal rate of Cu（Ⅱ）increases to 69.16%.The ordered porous ceramic has vertical directional pore structure like xylem and the mechanical support performance,and bamboo pulp fiber paper can provide the transpiration force like leaf.The experiment proves that it is feasible to use the bionic material in the remediation of contaminated soil and has potential application value in the remediation field of heavy metal contaminated soil. |
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