Solidification of electroplating sludge using alkali-activated pulverized fuel ash as cementitious binder

This work investigated the potential for utilization of alkali-activated PFA as solidification binder to treat electroplating sludge. The sludge was solidified using 30 wt.% of lime and 70 wt.% of PFA. Two alkali activators, Na₂SiO₃ and Na₂CO₃, were added at 0, 4, 6, and 8 wt.%. Results showed that early strength development of lime-PFA cements with Na₂SiO₃ and Na₂CO₃ was considerably higher than those without. Addition of electroplating sludge resulted in reduced strength. The strength reduction was greater when 4% Na₂SiO₃ activator was used than when 8% Na₂CO₃ activator was used. A higher pH of Na₂SiO₃ solution (pH=13.5) compared to that of Na₂CO₃ solution (pH=11.9) resulted in resolubilization of metal hydroxides from the electroplating sludge, which competed with calcium ion for soluble silicate. In addition, Pb, Cd, and Cu were not found in the toxicity characteristic leaching procedure (TCLP) leachates. Cr, Zn, and Fe were detected and in some cases Cr exceeded U.S. EPA allowable limits.     

Poly(divinylbenzene) Microencapsulated Octadecane for Use as a Heat Storage Material: Influences of Microcapsule Size and Monomer/Octadecane Ratio

Poly(divinylbenzene) (PDVB) microencapsulated octadecane (OD) (PDVB/OD) used as heat storage material were prepared by suspension polymerization at 70°C using benzoyl peroxide and polyvinyl alcohol as initiator and stabilizer, respectively. The influence of microcapsule size and divinylbenzene (DVB)/OD weight ratio on the microcapsule shape and thermal properties of encapsulated OD were considered. Thermal properties and thermal stability of PDVB/OD microcapsules were determined using differential scanning calorimeter (DSC) and thermogravimetric analyzer. The optical micrographs and scanning electron micrographs showed that the microcapsules have spherical shape only in the case of 50/50 (%w/w) of DVB/OD whereas they were nonspherical with the decreasing of DVB content. However, the core materials were still well encapsulated even increasing the OD content to 70%wt. From DSC analysis, in all cases, the melting temperature of encapsulated OD (28°C) was almost the same as that of bulk OD (30°C), yet it was quite different in the case of crystallization temperature (≤ 19°C and 25°C for encapsulated and bulk OD, respectively). The latent heats of melting and crystallization of encapsulated OD, in all conditions, were reduced from those of bulk OD (242 and 247 J/g, respectively).