摘要
以花生壳和中药渣为原料,分别于300、350、400、500、600℃下慢速热解制备生物炭,并表征其物理化学性质.研究不同p H、吸附时间和Cd(Ⅱ)浓度下生物炭对Cd(Ⅱ)的吸附特征.结果表明,随着热解温度的升高,生物炭的碳化程度增加,比表面积增大,含氧官能团数量减少,π共轭芳香结构更加完备,Ca和Mg等无机元素不断富集,矿物溶解性降低,导致了Cd(Ⅱ)在不同热解温度生物炭上吸附能力及机制的差异.随溶液p H的升高(2.0~6.0),生物炭对Cd(Ⅱ)的吸附量逐渐增加.吸附过程可分为快吸附和慢吸附两个阶段,吸附速度受膜扩散、颗粒内扩散和沉淀作用、离子交换等过程的控制.随热解温度的升高,快吸附在生物炭对Cd(Ⅱ)的吸附中所占比例逐渐降低.高温生物炭(≥500℃)中含氧官能团的锐减及难溶晶体矿物的形成降低了其对Cd(Ⅱ)的快吸附速率.沉淀和离子交换可能是低温生物炭(≤400℃)吸附Cd(Ⅱ)的主要机制;高温生物炭(≥500℃)中更完备的π共轭芳香结构增加了Cd-π作用对吸附的贡献,而难溶磷酸盐和碳酸盐的形成则降低了沉淀作用对吸附的贡献.这些研究结果为筛选对Cd(Ⅱ)具有高效去除或固持能力的功能生物炭(designer biochar)提供了重要的理论数据.
Ten biochars were prepared at different pyrolysis temperatures (300- 600℃) using peanut shells and Chinese medicine material residue as raw materials, and were characterized. Adsorption behavior of Cd(Ⅱ) on these biochars at different solution pHs, sorption times, and Cd(Ⅱ) concentrations was investigated. The C content, surface area, and aromaticity of the biochars increased with increasing pyrolysis temperature, while the amount of oxygen-containing functional groups decreased. In addition, the content of inorganic minerals (e. g. , Ca/ Mg carbonate or phosphate) was enriched, but their solubility was reduced with increasing pyrolysis temperature. As the solution pHs increased from 2. 0 to 6. 0, the amount of Cd(Ⅱ) adsorbed on the biochars gradually increased, and achieved the maximum at pH 6. 0. Adsorption processes could be divided into two stages: fast and slow sorption. The rate of Cd(Ⅱ) adsorption on these biochars was regulated by film and intraparticle diffusion, precipitation and ion exchange. With increasing temperature, the percentage of fast sorption to overall sorption of Cd(Ⅱ) gradually decreased. Sharp decrease of oxygen-containing functional groups and formation of insoluble crystalline minerals reduced the rate of fast sorption on the high-temperature biochars (≥500℃). For low-temperature biochars (≤400℃), precipitation and ion exchange were the dominant sorption mechanisms. For high-temperature biochars (≥500℃), more integrated π-conjugated aromatic structures enhanced the contribution of Cd-π interaction to the overall sorption, but the formation of phosphate and carbonate minerals probably weakened the sorption. These results will provide important information on screening biochars as engineered adsorbents to remove or immobilize Cd(Ⅱ) in contaminated water and soil.
出处
《环境科学》
EI
CAS
CSCD
北大核心
2014年第12期4735-4744,共10页
Environmental Science
基金
国家海洋公益性行业科研专项(201305021)
青岛市市南区科技局项目(2012-5-002-SW)
中国海洋大学青年教师基金项目(201413010)
中国博士后科学基金项目(2014M550374)
关键词
花生壳
中药渣
生物炭
吸附
镉
peanut shell
Chinese medicine material residue
biochar
adsorption
Cd(Ⅱ)
