表面改性非烧结生态砖材料对模拟城市暴雨径流中低浓度磷的吸附特性

Adsorption Characteristics of Low-Concentration Phosphorus in Simulated Urban Rainstorm Runoff by Surface Modified Non-Sintered Eco-Brick

为了寻求城市暴雨后地表径流中低浓度磷的去除方法,考察了粉煤灰、活性炭、沸石等材料对低浓度磷的吸附特性,进而利用筛选出的吸附材料对河岸护坡砖表面进行改性,制成非烧结生态砖材料,系统地研究了吸附材料添加量、磷酸盐浓度、反应时间等对生态砖材料吸附磷酸盐效率的影响,并探究了紫花苜蓿对生态砖表面磷酸盐的吸收能力.结果表明:①在3种吸附材料中,粉煤灰对磷酸盐的吸附效果最佳,3 h内其对磷酸盐的去除率分别比沸石、活性炭提高了54%、67%.②当生态砖表面搭载36 mg cm^2粉煤灰时,生态砖材料表现出最佳的磷酸盐吸附性能,比未搭载粉煤灰的生态砖材料对磷酸盐的去除率提高了14%.③生态砖材料对磷酸盐的吸附符合Freundlich吸附等温方程和颗粒内扩散方程,其对磷酸盐的吸附机理是由颗粒内扩散起主导作用的物理吸附.④在缺磷胁迫环境下,紫花苜蓿根系分泌出的柠檬酸将生态砖表面的磷酸钙晶体溶解,进而将其吸收进植物体内,15 d对生态砖表面磷的脱附比例为38.40%±0.37%.研究显示,粉煤灰改性的非烧结生态砖材料对磷酸盐具有较好的吸附效果,并且吸附的磷酸盐能够被植物所吸收可实现生态砖材料的天然再生.

In order to find out the removal method of low concentration phosphorus in surface runoff after urban heavy rain,The adsorption characteristics of fly ash,activated carbon,zeolite and other materials on low-concentration phosphorus were investigated,and the surface of the bank slope protection brick was modified by the selected adsorption materials to make non-sintered ecological brick materials.The effects of adsorption amount,phosphate concentration and reaction time on the adsorption efficiency of phosphate bricks were studied systematically.The absorption capacity of alfalfa on the surface of eco-bricks was also investigated.The results showed that:(1)Among 3 adsorbent materials,fly ash has the best adsorption effect on phosphate.In 3 hours,the removal rate of phosphate is 54%higher than that of zeolite and 67%higher than that of activated carbon.(2)When the ecological brick surface was loaded with 36 mg cm^2 fly ash,the eco-brick material showed the best phosphate adsorption performance,and the phosphate removal rate was increased by 14%compared with the ecological brick material without the fly ash.(3)The adsorption of phosphate by ecological brick material accords with the Freundlich adsorption isotherm equation and the intraparticle diffusion equation.The adsorption mechanism of phosphate is the physical adsorption dominated by intraparticle diffusion.(4)Under the condition of phosphorus deficiency stress,alfalfa secreted citric acid to dissolve the calcium phosphate crystal on the surface of ecological brick,and then absorbed it into the plant.The desorption ratio of phosphorus on the surface of ecological brick was 38.40%±0.37%in 15 d.Studies have shown that fly ash-modified non-sintered ecological brick materials have a good adsorption effect on phosphate,and the adsorbed phosphate can be absorbed by plants to achieve natural regeneration of ecological brick materials.