Preparation and characterization offoamed concrete with Ti-extracted residues and red gypsum
钛浸出物(TRs)和红石膏(RG)是二氧化钛生产中的工业废弃物，其处理过程繁杂，对环境造成了极大的影响。本研究使用普通硅酸盐水泥(OPC)和TRs、RG作为主要的三元复合胶凝材料来制备泡沫混凝土(FC)。研究了复合水泥的水化动力学、FC的机械性能和微结构。结果表明，生石灰和硫铝酸盐水泥(SAC)能够明显缩短复合胶凝材料的凝结时间，但是TRs的机械激发不能大幅缩短其凝胶时间。就FC而言，最近的技术参数为OPC:TRs:RG=10:45:45(质量比，下同)，生石灰2%，SAC4%，Na2SO4 0.4%，减水剂0.2%，泡沫4.6%，水胶比0.6。FC的最大抗压强度达到了2.14 MPa，比强度达到了4.91kN·m/kg(密度为437 kg/m3)。微结构分析表明，FC中互相连通的集合体为绒球状和花瓣状的水化凝胶，针状的钙矾石和未反应片状石膏。
The recycling of Ti-extractedresidues (TRs) and red gypsum (RG), which are the industrial wastes fromtitanium dioxide manufacturing industry, will avoid the increasing impact onthe environment due to their difficulty for disposal. In this paper, the ternaryblended binder mainly consisting of ordinary Portland cement (OPC), TRs and RGfor the preparation of foamed concrete (FC) was formulated in the laboratory.The hydration kinetics of blended cement, mechanical characteristics andmicrostructure of FC were investigated. The results indicated that quick limeand sulfoaluminate cement (SAC) evidently reduced the setting time of thecomplex binder, but mechanical activation for TRs could not substantiallyshorten those of blended binder. In the case of FC, the optimum technologicalparameters were proposed as follows: OPC: TRs: RG = 10:45:45 (by mass, the samebelow), quick lime 2%, SAC 4%, Na2SO4 0.4%, water reducer 0.2%, foam 4.6% and W/B0.60. The maximum compressive strength and specific strength of FC with densityof 437 kg/m3 reached up to 2.14 MPa and 4.91 kN·m/kg,respectively. Microstructure analysis revealed that the interconnected assemblagesin FC are floccular and petal-like hydrated gels, need-like ettringite andunreactive plate-like gypsum.
Effect of composite photo-catalysts preparedwith recycled clay brick sands and nano-TiO2 on methyl orange and NOxremoval
本研究的目的是为了使用循环黏土砖砂(RCBS)和纳米TiO2开发一种复合光催化剂。RCBS来自于建筑和拆迁废弃物(C&DW)。为了比较，同样使用了河砂（RS）。RCBS和RS浸泡在含有0%, 0.5%, 1.0%, 2.5%和5.0%（质量含量）的纳米TiO2溶液中以制备RCBS基和RS基复合光催化剂。接着确认RCBS和RS吸附纳米TiO2的含量。研究了复合光催化剂去除甲基橙和NOX的光催化活性。结果表明，RCBS和RS吸附的纳米TiO2量随着纳米TiO2浓度增加而增加。但是，光催化活性和RCBS,RS吸附的纳米TiO2量呈非线性关系。浸泡在1% TiO2溶液的复合光催化剂表现出最高的甲基橙和NOx去除效率。令人感兴趣的是，在同样条件下，RCBS基复合光催化剂甚至比纯的纳米TiO2光催化效率更高：甲基橙去除率60%和NOx去除率50%。总而言之，制备的复合光催化剂不但光催化活性好，而且提高了建筑材料中RCBS的利用价值。
This research aims todevelop a composite photo-catalyst using recycled clay brick sands (RCBS) andnano-TiO2. The RCBS was sourced from construction anddemolition wastes (C&DW). For comparison, river sands (RS) were also used.Both RCBS and RS were soaked in 0%, 0.5%, 1.0%, 2.5%, and 5.0% (by weight)nano-TiO2 solutions to produce RCBS based composite and RSbased composite photo-catalysts. The amount of nano-TiO2 absorbed by RCBS and RS was then determined. Thephotocatalytic methyl orange removal and NOx removal activities of the preparedcomposite photo-catalysts were investigated. The results showed that the amountof nano-TiO2 absorbed by RCBS and RS increased withincreasing the concentration of nano-TiO2 solution. However, a non-linearrelationship between the photocatalytic activities and the amount of TiO2 absorbed by RCBS and RS was observed. Thehighest methyl orange and NOxremoval were observed on the composite photo-catalysts soakedin 1.0% nano-TiO2solutions. Interestingly, the optimal RCBS basedcomposite photo-catalysts were even superior to pure nano-TiO2 in terms of both methyl orange removal (60%) andNOxremoval (50%) under the same conditions. Overall,the developed composite photo-catalysts not only possess an enhancedphotocatalytic activity, but also generate value-added recycling of RCBS inconstruction materials.