Adsorption Characteristics Of Phosphorus By Wasted Bricks With Low Temperature Conditions

It is necessary to conduct the study on the removal of phosphorus from water by wasted bricks in bioretention in the context of the continuous acceleration of the urbanization process and the increasing of the reserves of the abandoned buildings bricks and the increasing eutrophication of the water.The hydraulic conductivity of wasted bricks was determined by self-make device.Phosphorus adsorption isotherm and its kinetics were examined and effects of initial phosphorus concentration,adsorbent particle size,pH,temperature and coexisted anions were investigated to understand the characteristics of phosphorus adsorption onto red bricks,concrete and burm-free bricks.In addition,organic materials were added intending to increase the removal of phosphorus.Phosphorus adsorption mechanism on different substrates were explored by the means of adsorption theromdynamics and FTIR.The main results of this study are as follows.(1)Particle size has a significant effect on hydraulic conductivity.Hydraulic conductivity increased with the increase of particle size.With the increase of the mass ratio of the brick to the soil,the tendency of hydraulic conductivity increase first and then decrease.hydraulic conductivity of various proportions meet the requirements of bioretention.(2)The increase of initial phosphorus concentration,temperature and the decrease of particle size will lead to the increase of adsorption capacity for burn-free bricks、concrete and red bricks.Reduction of phosphorus removal efficiency on burn-free bricks and concrete can be observed with the increase of coexisted anions concentration.The effect of pH on the adsorption capacity of three kinds of bricks is less.(3)Through the kinetic model fitting,the first order dynamic model and the two order dynamic model can well describe the adsorption kinetics of three kinds of particle size burn-free bricks and concrete.Both Langmuir and Freundich can well describe the adsorption isothermal characteristics of three kinds bricks.Maximum saturated adsorption capacity of the theory of burm-free bricks、concrete and red bricks according to Langmuir is respectively 492mg/kg、262.06mg/kg and 198mg/kg.△G0<0,△H0>0 indicates the adsorption process of brick to phosphorus is spontaneous and endothermic.(4)The adsorption capacity of phosphorus on burn-free bricks and concrete decreased after adding organic material,the adsorption capacity of red bricks increased with the same conditon.meanwhile the time for adsorption balance increased.The difference of IR before and after adsorption indicate that phosphorus adsorption by red bricks was mainly physical adsorption.the mechanism of phosphorus adsorption on burn-free bricks and concrete was attributed to chemical adsorption and the dominating mechanism was chemical reaction between CaO、Fe2O3 and H2PO4.