生物还原-化学沉淀耦合反应制备纳米硫化镉和硫化铅

本文应用生物还原-化学沉淀耦合反应成功制备了高纯纳米硫化镉和硫化铅，EDTA(Ethylene Diamine Tetraacetic Acid)的加入为高浓度金属离子条件下的生物制备提供了保证。研究表明，在0.012 5~0.037 5 mol·L^-1的较低浓度范围内镉浓度增加促进了硫酸根的生物还原和硫化镉的生物制备；但0.05 mol·L^-1的高浓度镉则抑制了SRB的生物活性并降低了硫化镉的生成量。随着厌氧还原反应的进行，微溶的白色硫酸铅沉淀逐渐转化为不溶的黑色硫化铅沉淀，导致纳米硫化铅的生成。硫化镉微球的一次粒子约为10~20 nm，二次粒子平均粒径400 nm，PAM(polyacrylamide)的加入使得二次粒子分布更为均匀。硫化铅微粒二次粒子约为40 nm，PAM的加入没有改变粒子大小，但使得粒子形态由球形变为方形。生物还原-化学沉淀耦合反应对于金属硫化物的制备具有一定的普适性，因而显示出良好的应用前景。

Nano Sized CdS and PbS Particles: Preparation by Coupling of Biological Reduction and Chemical Precipitation Mediated with EDTA

High-purity nano CdS and PbS particles were synthesized using a coupling reaction of biological reduction and chemical precipitation mediated with EDTA referred as CRBRCP-EDTA process. The results showed that the concentration increase of Cd²⁺, between 0.012 5 and 0.037 5 mol·L^-1, enhanced the bioreduction of SO₄^2- and CdS bioproduction. But the high concentration of Cd²⁺, 0.05 mol·L^-1, inhibited the biological activity of sulfate reduction bacteria (SRB) and reduced CdS production. In the reaction of anaerobic reduction, slightly soluble PbSO₄ sedimentation gradually transformed into insoluble PbS sedimentation, leading to nano PbS production. The diameter of CdS solid spheres is 10~20 nm for primary particles and around 400 nm for secondary particles. When polyacrylamide (PAM) was incorporated in the process, the distribution of secondary particles diameter of CdS were more uniform. The secondary particles diameter of PbS solid spheres is about 40 nm, and it did not change when PAM incorporated, but the morphology transformed from sphere to cube. The bioproduction of metal-sulfide using CRBRCP-EDTA process can be extended to other metals, leading to a bright prospect for wider application.