Study On Preparation Of Water Environmental Phosphorus Removal Materials By Calcining Water Treatment Plant Sludge

Phosphorus?P?is the main limiting factor for eutrophication of water body,so reducing P concentration is an effective measure to control eutrophication.Water treatment plant sludge?WTPS?has a strong adsorption capacity for P,and the application of it to reduce phosphorus concentration in water environment is a hot topic at present.However,our project group recently found that WTPS have the defect that it release ammonia nitrogen and organic matter in the process of P removal.To solve the problem,WTPS was calcined to prepare calcined water treatment plant sludge?C-WTPS?.The optimum calcining parameters of C-WTPS were determined,and the physical and chemical properties of C-WTPS were characterized.The performance and channel of P removal in C-WTPS were studied.The adsorbed P and metal release in C-WTPS were investigated.The main conclusions are as follows.?1?The optimum calcination parameters were calcining temperature at 400?and calcining time with 2.5 h in the range of calcining temperatur between 100?to800?and calcining time from 0.5h to 4h.A lot of ammonium nitrogen and organic matter were removed from WTPS by calcination,which effectively solved the problem of ammonia nitrogen and organic matter release,and also increased the amount of P adsorption.In addition,the change of ammoniacal nitrogen and organic matter in WTPS did not affect the performance of calcination.?2?WTPS and C-WTPS were characterized by using SEM-EDS,XRF,XRD and BET.The results showed that?)the calcination caused a lot of cracks on the surface of WTPS,increased the specific surface area,pore volume and pore size of WTPS,the mass fraction of the surface C and N elements decreased by 5.52%and 1.26%respectively,and the mass fraction of Al and Fe increased by 2.30%and 0.54%,respectively.?)Si,Al and Fe were the main components of WTPS and C-WTPS.?)The main phase compositions of WTPS and C-WTPS are Kaolinite?Al₂?Si₂O₅??OH?₄?and SiO₂.?3?The results of main influencing factors for C-WTPS dephosphorization showed that?)the higher the initial concentration of P,the greater the P adsorption capacity of C-WTPS,and the greater the P adsorption capacity of C-WTPS than WTPS.?)The greater dosage,the smaller the P adsorption capacity of C-WTPS.?)The larger the initial pH,the smaller the P adsorption capacity of C-WTPS.When the initial pH>10,C-WTPS releases P to the water body.?)The higher the temperature,the higher the P adsorption capacity of C-WTPS.?4?The adsorption process of P by C-WTPS was found to be followed the pseudo-second-order model,which showed that the adsorption of P is mainly controlled by chemical action.The adsorbed P in C-WTPS existed in mostly non apatite inorganic P?NAIP?.The adsorption rate of P in C-WTPS is faster than that of WTPS,and the adsorption equilibrium time is reduced by 48h.The Langmuir and Freundlich equation can describe well the P adsorption process of C-WTPS,and the correlation coefficients both exceeded 0.9.In the range of 0.5-20mg/L initial concentration of phosphorus,the maximum P adsorption amount on C-WTPS was3.34mg/g,according to the Langmuir isothermal model fitting results,which increased by 1.25mg/g than WTPS.The channel of P removal was mainly Fe and Al oxides and hydroxide adsorption,the adsorbed P mainly existed in NAIP??5?The results of the study on the release of adsorbed P and metal in C-WTPS showed that the greater initial pH of the solution,the greater the amount of adsorbed P in C-WTPS release.In anaerobic,anoxic and aerobic conditions,there is no release of adsorbed P in C-WTPS,and the concentration of DO in the solution has no significant effect on release of adsorbed P in C-WTPS.There is release of Mn in C-WTPS,especially in acid conditions,the release amount is greater.