Bioactive Cellulose Nanocrystal-Poly(ε-Caprolactone) Nanocomposites for Bone Tissue Engineering Applications.

3D-printed bone scaffolds hold great promise for the individualized treatment of critical-size bone defects. Among the resorbable polymers available for use as 3D-printable scaffold materials, poly(ε-caprolactone) (PCL) has many benefits. However, its relatively low stiffness and lack of bioactivity limit its use in load-bearing bone scaffolds. This study tests the hypothesis that surface-oxidized cellulose nanocrystals (SO-CNCs), decorated with carboxyl groups, can act as multi-functional scaffold additives that (1) improve the mechanical properties of PCL and (2) induce biomineral formation upon PCL resorption. To this end, an in vitro biomineralization study was performed to assess the ability of SO-CNCs to induce the formation of calcium phosphate minerals. In addition, PCL nanocomposites containing different amounts of SO-CNCs (1, 2, 3, 5, and 10 wt%) were prepared using melt compounding extrusion and characterized in terms of Young's modulus, ultimate tensile strength, crystallinity, thermal transitions, and water contact angle. Neither sulfuric acid-hydrolyzed CNCs (SH-CNCs) nor SO-CNCs were toxic to MC3T3 preosteoblasts during a 24 h exposure at concentrations ranging from 0.25 to 3.0 mg/mL. SO-CNCs were more effective at inducing mineral formation than SH-CNCs in simulated body fluid (1x). An SO-CNC content of 10 wt% in the PCL matrix caused a more than 2-fold increase in Young's modulus (stiffness) and a more than 60% increase in ultimate tensile strength. The matrix glass transition and melting temperatures were not affected by the SO-CNCs but the crystallization temperature increased by about 5.5°C upon addition of 10 wt% SO-CNCs, the matrix crystallinity decreased from about 43 to about 40%, and the water contact angle decreased from 87 to 82.6°. The abilities of SO-CNCs to induce calcium phosphate mineral formation and increase the Young's modulus of PCL render them attractive for applications as multi-functional nanoscale additives in PCL-based bone scaffolds.

Coal fly ash and synthetic coal fly ash aggregates as reactive media to remove zinc from aqueous solutions.

Coal fly ash (CF) and synthetic coal fly ash aggregates (SCFAs) were evaluated as low-cost reactive media for the remediation of groundwater contaminated with Zn. The SCFAs were prepared by mixing CF, sodium silicate, and deionized (DI) water. Serial batch kinetic and static tests were conducted on both CF and SCFAs, under various conditions (i.e., pH, initial Zn concentration, reaction time, and solid dosage), using Zn(NO(3))(2).6H(2)O solutions. Serial column tests were also conducted on both CF and SCFAs. The final rather than the initial pH of the solution had a greater effect on the removal of Zn. At pH>7.0, the removal of Zn was due to precipitation, whereas at <7.0, the removal of Zn was due to adsorption onto the reactive media. The removal of Zn increased with increasing dosage of the reactive medium and decreasing initial Zn concentration. The results of the column and batch tests were comparable. Preferential flow paths were observed with CF, but not SCFA. The hydraulic conductivity of CF was more significantly decreased than that of SCFA with increasing dry density of the specimen.

Environmental feasibility of using coal ash as a fill material to raise the ground level.

Batch leach tests (BLTs) and column leach tests (CLTs) were conducted on bottom ash (BA), lagoon ash (LA), soil (S), and bottom ash-soil (BA-S) and lagoon ash-soil (LA-S) mixtures to evaluate the environmental feasibility of using these as fill materials to raise the ground level at construction sites. For the BLTs, the leachability of the elements (i.e., Cr, Mn, Ni, and Zn) generally increased with decreasing pH from 6.3 to 3.0. In addition, the concentration of all the elements analyzed in the leachates increased with decreasing the liquid-to-solid (L/S) ratio. Freezing-thawing cycles had no significant effect on the leachability of the elements found in the BLTs. The initial concentrations of the leachates from the CLTs were higher than those of the leachates from the BLTs regardless of the materials tested due to the lower L/S ratio. The initial concentrations of As, Ni, Mn, Se, Cl-, and SO4(2-) in the leachates from the CLTs for the LA, BA, and LA-S and BA-S mixtures exceeded the drinking water standards (DWSs), which suggests that these materials may pose a risk to groundwater when these materials are used in areas where there is little dilution.