Preparation Of Waterworks Sludge Supported Nanoscale Zerovalent Iron And Study On The Performance Of Removing Cr(?) From Water

The waterworks sludge is solid waste generated after the drinking water plant produces drinking water.Nano-zero-valent iron is a new type of nano-material with high activity and strong reduction,but it has the disadvantage of easy oxidation and easy agglomeration.The use of waterworks sludge as a supporter of nano-zero-valent iron is beneficial to reduce the agglomeration and oxidation of nano-zero-valent iron,improve the stability of nano-zero-valent iron,and achieve the goal of efficiently removing pollutants.High-temperature calcination and acidification of hydrochloric acid allow the waterworks sludge to have a larger specific surface area to increase the loading sites for nano-zerovalent iron.In the experiment,liquid phase reduction method was used to reduce iron ions on the surface of waterworks sludge to obtain modified waterworks sludge-supported nano-zero-valent iron adsorbent(MWS-n Z?).The physical and chemical properties of the adsorbent were investigated by SEM,EDS,BET,XRD,XPS and FTIR.The adsorption performance of the adsorbent was investigated by p H,initial concentration,dosage and reaction time as controlling factors.Adsorption thermodynamics and adsorption kinetics models and adsorption mechanisms were also investigated.The SEM and BET results showed that the surface of the waterworks sludge had a large smooth pore size and a small specific surface area.The surface roughness of the MWS-n Z? surface was small and the specific surface area was large.Comparing the FTIR and XRD patterns of the waterworks sludge and MWS-n Z?,it is found that the nano-zero-valent iron has a peak at the corresponding position,which proves that the nanozero-valent iron has been loaded on the waterworks sludge.The characterization of the supported adsorbent after adsorption of Cr(?)by XPS found that Cr(?)appeared on the surface of the adsorbent,indicating that the nano-zero-valent iron participates in the oxidation-reduction reaction of the adsorption process.The experimental conditions have different effects on the removal of Cr(?)by the adsorbent.The p H is the key factor affecting the removal effect of MWS-n Z?,which is characterized by low p H to promote adsorption and high p H to inhibit adsorption.The experimental data showed that when the p H was 2 and the initial concentration of 0.3g/L was 50mg/L,the adsorption amounts of the waterworks sludge and MWS-n Z? reached 8.2 mg/g and 51 mg/g,respectively.The experimental data were brought into the adsorption kinetics,adsorption isotherm and adsorption thermodynamic model.The fitting results showed that both the waterworks sludge and MWS-n Z? were spontaneous adsorption processes,and the pseudo-second-order were suitable for describing various adsorbents in this study.The adsorption process,Langmuir and Freundlich isotherm adsorption models are applicable to the description of the mechanism of the waterworks sludge and MWS-n Z?.The removal mechanism of Cr(?)by waterworks sludge and MWS-n Z? is different.The waterworks sludge with adsorption capacity is mainly used for the removal of Cr(?)by adsorption.Removal of Cr(?)by the adsorption and reduction of MWSn Z? adsorbent by first adsorbing and then redoxing to form Cr(?)The modified waterworks sludge-supported nano-zero-valent iron adsorbent has excellent removal effect on Cr(?)in the water.Therefore,waterworks sludge can be used as a supporter for the utilization of waterworks sludge as a supporter of nano-zero-valent iron.