Activated carbon (AC) modification has been intensively studied in order to design carbon electrodes with enhanced electrochemical performance. Hexadecyltrimethylammonium bromide (HDTMA) and Tween 80 were employed for enhancing the surface activity of AC via synergism. The synergistic effects of the mixed surfactants on AC surface activity in the light of interface behaviors were studied. Both field emission scanning electron micrographs and FTIR spectra indicated a successful adsorption of loaded surfactants. AC gained a good wettability originated from the surfactants, especially in the binary mixture (T80-HDTMA). The zeta potential results unveiled the positive charge density enhancement in the mixed surfactants system. Isoelectric point and point of zero charge implicate heterogeneous distribution of charges and the extent of surfactants treatment. Tween 80 displayed a significant size control dependence on AC particles. Electrochemical characterization revealed a higher specific capacitance and a decaying resistance of specific capacitance in AC-T80-HDTMA than AC-HDTMA at high concentration. In 5 g L⁻¹ of NaCl, AC-T80-HDTMA (0.01 : 0.01 mM) exhibits the specific capacitance of 209.79 F g⁻¹, at 0.8 V whereas AC-HDTMA (0.01 mM) and AC exhibited 186.5 F g⁻¹, 178.9 F g⁻¹, respectively. Moreover, the stability testing reveals a strong attachment of HDTMA in AC-T80-HDTMA than AC-HDTMA with the loss of 0.32% and 1.32%, respectively. The hypothetical synergistic mechanism of surfactants adsorption on the surface of AC was depicted as hydrophobic interaction and steric stabilization being the main keys for the synergy between cationic and nonionic surfactants. This study demonstrates the beneficial effects of mixed surfactants on AC electrode properties and discloses the impact on electrochemical performance.

Bacterial infection is currently considered to be one of the major reasons that leads to the failure of guided bone regeneration (GBR) therapy. Under the normal condition, the pH is neutral, while the microenvironment will become acid at the sites of infection. Here, we present an asymmetric microfluidic/chitosan device that can achieve pH-responsive drug release to treat bacterial infection and promote osteoblast proliferation at the same time. On-demand release of minocycline relies on a pH-sensitive hydrogel actuator, which swells significantly when exposed to the acid pH of an infected region. The PDMAEMA hydrogel had pronounced pH-sensitive properties, and a large volume transition occurred at pH 5 and 6. Over 12 h, the device enabled minocycline solution flowrates of 0.51–1.63 µg/h and 0.44–1.13 µg/h at pH 5 and 6, respectively. The asymmetric microfluidic/chitosan device exhibited excellent capabilities for inhibiting Staphylococcus aureus and Streptococcus mutans growth within 24 h. It had no negative effect on proliferation and morphology of L929 fibroblasts and MC3T3-E1 osteoblasts, which indicates good cytocompatibility. Therefore, such a pH-responsive drug release asymmetric microfluidic/chitosan device could be a promising therapeutic approach in the treatment of infective bone defects.

Effects of thermal hydrolysis temperature on the physical properties of municipal sludge was further studied by a series of experiments. There was a decrease in bound water content with an increase in hydrolysis temperature, while there was an increase in pH at temperatures below 120 °C, and a decrease at temperatures exceeding 120 °C. An analysis of settleability, centrifugation and vacuum filtration of the treated sludge indicated that the threshold temperature was 120 °C, which was the same as the temperature for the bound water content and particle size. In addition, raw sludge with a solids content of 100 g/L, exhibited significant non-Newtonian fluid characteristics. At thermal hydrolysis temperatures exceeding 120 °C, non-Newtonian fluid characteristics including liquid and solid characteristics were significantly weakened. The consistency index (k) decreased from 5.90 Pa·s to 0.068 Pa·s, while the flow index (n) increased from 0.31 to 0.74, suggesting that thermal hydrolysis sludge was much closer to Newtonian fluids compared to raw sludge. Modification of bound water content, particle size and viscosity with hydrolysis temperature, revealed the nature of improved dewaterability by thermal hydrolysis. The fractal dimension of the sludge floc increased from 2.74 to 2.90, meaning that the floc became more compact after thermal hydrolysis.