Influence of Impurity Na2O on Crystalline Structure of Cordierite Synthesized from Aluminum Sludge

Waste aluminum sludge, talc powder and clay were used to synthesize cordierite in this research. The impurities, such as Fe2O3, CaO, K2O and Na2O, in the raw materials have some influence on the structures and properties of the materials. In this paper, we mainly discuss the impact of impurity Na2O on the structure of cordierite, based on which the permitted amount of Na2O was determined. The results show that Na2O with the amount less than 0.6% has little influence on the cordierite formation; while when its amount increasing from 0.6% to 0.7%, the content of cordierite decreases from 86% to 84% and the permitted amount for Na2O in the raw materials is less than 6% with the best amount less than 0.3%. X’pert plus software analysis results show the impurity Na2O has no influence on the cordierite space group and only the lattice parameters vary slightly; but it has much influence on the structure of Mg-Al spinel and the lattice parameters are much changed.

Influence of Pore-expansion Agent on the Structure and Performance of Activated Alumina Synthesized from Waste Aluminum Sludge

The chemical compositions of the sludge after treatment are tested by fully chemical analysis techniques. Its crystalline phase structure changes of the sludge calcined at different temperature are characterized by XRD method. Nitrogen gas isothermal adsorption method （77 K） is applied to measure the influences of ammonium bicarbonate on specific surface area and pore structure of activated alumina synthesized from waste aluminum sludge. The result shows that the amount of Al2O3 in the sludge accounts for more than 94%, and Na2Owt% in a 0.1-0.2% range. By calcining raw sludge at 600℃, monophase γ-Al2O3 is obtained. And this can satisfy the performance requirements of activated alumina adsorbent. The specific surface area of the specimen with NH4HCO3 added has expanded from 179 to 249 m^2/g and the pore volume from 0.25 to 1.11 cm^3/g as well as the average pore diameter from 5.6 to 17.8 nm. All these show that NH4HCO3 is an effective pore-expansion agent to remarkably improve the structure and performance of activated alumina synthesized from waste aluminum sludge.

Resource utilization of drinking water treatment aluminum sludge in green cementing materials: Hydration characteristics and hydration kinetics

As a byproduct of water treatment,drinking water treatment aluminum sludge(DWTAS)has challenges related to imperfect treatment and disposal,which has caused potential harm to human health and the environment.In this paper,heat treatment DWTAS as a supplement cementitious material was used to prepare a green cementing material.The results show that the 800℃ is considered as the optimum heat treatment temperature for DWTAS.DWTAS-800℃ is fully activated after thermal decomposition to form incompletely crystallized highly activeγ-Al_(2)O_(3) and active SiO_(2).The addition of DWTAS promoted the formation of ettringite and C-(A)-S-H gel,which could make up for the low early compressive strength of cementing materials to a certain extent.When cured for 90 days,the compressive strength of the mortar with 30% DWTAS-800℃ reached 44.86 MPa.The dynamic process was well simulated by Krstulovi′c-Dabi′c hydration kinetics model.This study provided a methodology for the fabrication of environmentally friendly and cost-effective compound cementitiousmaterials and proposed a“waste-to-resource”strategy for the sustainable management of typical solid wastes.

Potential acute effects of suspended aluminum nitride (AlN) nanoparticles on soluble microbial products (SMP) of activated sludge

The study aims to identify the potential acute effects of suspended aluminum nitride（Al N）nanoparticles（NPs） on soluble microbial products（SMP） of activated sludge.Cultured activated sludge loaded with 1,10,50,100,150 and 200 mg/L of Al N NPs were carried out in this study.As results showed,Al N NPs had a highly inverse proportionality to bacterial dehydrogenase and OUR,indicating its direct toxicity to the activated sludge viability.The toxicity of Al N NPs was mainly due to the nano-scale of Al N NPs.In SMP,Al N NPs led to the decrease of polysaccharide and humic compounds,but had slight effects on protein.The decrease of tryptophan-like substances in SMP indicated the inhibition of Al N NPs on the bacterial metabolism.Additionally,Al N NPs reduced obviously the molecular weight of SMP,which might be due to the nano-scale of Al N.