矿山酸性废水中多孔连通型粉煤灰泡沫混凝土的原位合成与重金属、硫酸根离子高效共去除

Acid mine drainage (AMD) is rich in heavy metal ions and sulfate ion. The conventional treatments, such as neutralization, precipitate, etc., are costly and highly material consumed with serious secondary pollution. In accordance with the idea of " waste control by waste ", if we can make use of the synergistic effect of fly ash and cement hydration products such as calcium silicate hydrate (C-S-H) and CaAl-LDHs to in-situ immobilize heavy metal ions and sulfate ion in wastewater and simultaneously produce connected porous foam concrete block with fly ash, the economical and environmentally friendly wastewater self-purification can be achieved. In order to understand the ion exchange process, surface adsorption behaviors, interlayer effect and synergistic mechanisms during the removal of pollutants from simulated and practical wastewater by CSH, CaAl-LDHs and fly ash, the macroscopic analysis of the solution components combined with solid product microcosmic characterizations will be proposed in this work. Meanwhile, the influences of different parameters, for instance, the ratio of fly ash, cement and vesicant and the addition ways of vesicant on the hydration pH, ratio of calcium to silicon and pollutant removal efficiency will be investigated. The influence of other components in wastewater on the formation of foam block will be explored, followed by the study of involved mechanisms. The synthesis and control mechanisms will be revealed. This project will provide instructions and optimizations for the utilization of porous foam concrete block with fly ash on the AMD treatment. The resulting products that contain pullutants can be reused as as green building materials without secondary pollution.

矿山酸性废水多富含重金属及硫酸根离子，中和、沉淀等常规处理法物耗、成本高，且二次污染严重。秉承“以废治废”的思想，若能借助粉煤灰、水泥水化产物C-S-H和钙铝LDHs的协同效应，在原位固定废水重金属及硫酸根离子的同时，诱导多孔连通型粉煤灰泡沫混凝土形成，将经济、环保地实现废水自净化。为此，本研究拟采用溶液组分宏观分析与固体产物微观表征相结合方法，以搞清C-S-H、钙铝LDHs及粉煤灰在模拟及实际废水中作用于污染物时发生的离子交换、表面吸附、层间效应及其协同作用机制；探寻粉煤灰、水泥及发泡剂配比、发泡剂添加方式对水化pH、硅钙比及污染物去除效率影响及作用机制；明晰废水体系其它组分对泡沫混凝土形成的影响及其作用机制。本项目将揭示酸性矿山废水中多孔连通型粉煤灰泡沫混凝土的合成机理及其控制机制，有望指导、优选合成工艺使其最宜于酸性废水处理，且容纳污染物的产物，可作为绿色建材资源化回收，无二次污染。

矿山酸性废水多富含重金属及硫酸根离子，中和、沉淀等常规处理法物耗、成本高，且二次污染严重。秉承“以废治废”的思想，基于“合成-净化”一体化水处理设计理念，本项目借助粉煤灰、水泥水化产物C-S-H和钙铝LDHs的协同效应，通过调控制备可在原位固定酸性废水重金属及硫酸根离子且能调节pH的多孔连通型粉煤灰泡沫混凝土而实现矿山酸性废水达标排放。本项目研究成果主要包括以下：1）通过优化粉煤灰、水泥、发泡剂等原料及用量，确定粉煤灰掺量为30%、水灰比为0.55、发泡剂选择CTAB时可制得连通孔隙率高于18%、低干密度低于850kg/m3、适用于废水治理的多孔连通型粉煤灰泡沫混凝土。2）通过等温吸附、吸附动力学及对环境影响因子等考察，确定了粉煤灰和水泥对Cu2+去除的最佳投加量分别为30g/L和1.5g/L，其中粉煤灰和水泥对Cu2+吸附符合Langmuir模型，和假二级动力学，为典型的单分子层化学吸附；粉煤灰和水泥的最大吸附量分别为9.12和16.25g/mg；由于粉煤灰表面负电性及水泥水化可释放硫酸根离子，二者对SO42-基本无去除能力。3）多孔连通型粉煤灰泡沫混凝土对Cu2+和SO42-的去除结果表明多孔连通型粉煤灰泡沫混凝土对Cu2+的吸附过程符合Langmiur模型以及假二级动力学模型，属于单分子层化学吸附，最大吸附量可达22.42mg/g；多孔连通型粉煤灰泡沫混凝土对SO42-去除率高于19%，去除量可达3.36mg/g，明显高于纯粉煤灰、水泥等对水体SO42-去除效率。此外，结合Zeta电位、XRD、FTIR、SEM等对反应前后样品的结构、组分及形貌测试，确定静电作用和沉淀是多孔连通型粉煤灰泡沫混凝土对酸性矿山废水中铜及硫酸根去除的主要作用机理，而粉煤灰及水泥在水化中高液相pH也有效调节了体系pH。4) 在实验室模拟实际矿山酸性废水体系中，多孔连通型粉煤灰泡沫混凝土对Cu2+及SO42-去除量分别为24.67mg/g和4.32mg/g，体系pH明显提高至7.4。本项目研究结果可为矿山酸性废水的深度处理提供理论指导，为粉煤灰等固废的资源化利用提供新途径。