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The crux to practical application of geopolymer adsorbents for antibiotics that are easily protonated and deprotonated is to clarify the dynamic adsorption mechanism of geopolymer with intrinsic alkaline release. The adsorption properties, adsorption mechanism, adsorption-desorption cycle and waste adsorbent regeneration based on the geopolymer adsorbent for adsorbing tetracycline under the spontaneous dynamic pH conditions were systematically investigated by experiment, characterization and density functional theory. The results confirmed that the structures of tetracycline depended on dynamic pHs of adsorption systems changed by geopolymer adsorbent. The electrostatic interaction assisted by hydrogen-bonding and n-π interaction dominated the adsorption process when the dynamic pHs were less than 7. And the hydrogen-bonding and n-π interaction provided the possibility of weak adsorption effect in highly alkaline environments. The geopolymer powder exhibited outstanding adsorption efficiency (∼95.62%, 30 min) due to the strong electrostatic adsorption between electronegative skeleton of geopolymer and zwitterions species tetracycline under dynamic pH range of 4–6.3 and fitted the pseudo-second-order model. The outstanding competitive adsorption properties in NaCl solution, adsorption (4 times)-desorption (3 times) cycle properties and regenerative property of waste adsorbent were exhibited. The mechanism study based on the dynamic pHs which is closer to actual conditions can provide important reference for practical application of easy preparation and low cost geopolymer adsorbents. [Display omitted] • A novel geopolymer adsorbent systems close to the practical application condition was proposed. • The electrostatic interaction assisted by hydrogen-bonding and n-π interaction dominated the adsorption of tetracycline. • The adsorption properties were maintained 93.20% (20 min) after adsorption (4 times)-desorption (3 times) cycle. • The regeneration strategy of geopolymer adsorbent by combining geopolymer precursor and waste geopolymer was provided. [ABSTRACT FROM AUTHOR]

Si 2 N 2 O composites were achieved via direct ink writing technique and pressureless sintering. The design and optimization of inks and the effect of mass ratio of Si 3 N 4 and SiO 2 on the phase composition, microstructure, mechanical properties and dielectric properties of composites were systematically investigated. The inks exhibit superior stability and printability. Increasing SiO 2 content facilitated densification and enhancement of mechanical property. The generation of β-Si 3 N 4 and Si 2 N 2 O and the nucleation of cristobalite were restrained by high content SiO 2. The ceramic composites with the flexural strengths from 74.1MPa to 104.9MPa and low dielectric constant (≤4.68) were fabricated. This strategy provides a systematic reference for synthesis of high-performance porous Si 2 N 2 O composites based on the DIW. [ABSTRACT FROM AUTHOR]

Porous Si 2 N 2 O ceramics strengthened by directional β-Si 3 N 4 are fabricated by direct ink writing technique and seeding method. Slurries prepared with different contents of β-Si 3 N 4 grains exhibited superior printing behavior. The degree of orientation of β-Si 3 N 4 grains increased with the increase of grains content. The mechanical properties of the porous Si 2 N 2 O ceramic are effectively improved by interspersed β-Si 3 N 4 grains and present anisotropy. This novel strategy provides a reference for fabricating high-performance anisotropic complex structure ceramics. [ABSTRACT FROM AUTHOR]

A novel, efficient, versatile strategy was carried out to fabricate highly porous ceramic parts based on the combination of strong colloidal gel ink fabricated with high boiling point organic solvents and DIW technique. The preparation and optimization of inks and the effect of heating temperature on the phase composition, microstructure, mechanical properties and dielectric properties of ceramic parts were systematically investigated. The strong colloidal ink exhibits excellent ambient stability and printability. The sintering temperatures bring about the evolution of phases, structural mechanical properties and dielectric properties of ceramic parts. Ultimately, Si 2 N 2 O single wall ceramic parts with a frame density of 1.07˜1.14 g/cm3 and an apparent porosity of 53.13 ± 1.29% were successful fabricated. The dielectric constant and dielectric loss of Si 2 N 2 O sample (1650℃) are only 4.24 and 0.0049, respectively. This strategy provides a reference for in-situ synthesis of high-performance porous ceramic components based on the DIW. [ABSTRACT FROM AUTHOR]

Water remediation using semiconductor photocatalysts under visible light (VL) irradiance appears as a more sustainable technology option due to the greater penetration depth. Consequently, the overall band spectrum of VL has received significant attention to providing solutions to secure clean water resources over the past few decades. This research developed an innovative approach to enhancing the visible light susceptibility of semiconductor-based photocatalytic composites Ag 10 Si 4 O 13 /TiO 2 (ASO/TO). The intrinsic properties of TO and electron donor ability of ASO lend synergistically to the generation of a narrow bandgap semiconductor. A feasible wet-chemistry method was found to engineer the electronic properties of ASO/TO under VL for rapid decolorization of methylene blue (MB). Inhibition experiments with several agents confirmed that the decolorization proceeds through the generation of hydroxyl radical species assisted by hole carrier generation at the ASO junction. The rate of MB decomposition followed a pseudo-first-order kinetic profile (98.2% within 35 mins under ambient conditions with 5 ppm of 2:1 ASO/TO and 20 ppm of MB). The XRD/XPS spectroscopic analysis confirms the electronic polarization of distorted SiO 4 tetrahedral units coordinated to Ag-O, forming a double dumbbell double-helical structure. The staggered bandgap of these composite photocatalysts is associated with the Ag-Ag d10/sp hybridization and dispersive conduction band. At the same time, the 2p orbitals of TiO 2 showed a less dispersive band due to the availability of d -orbitals. The generated Ag 10 Si 4 O 13 (ASO) based ferroelectric materials allow amplifying its frequency due to internal polarization along the c-axis. The electrochemical evaluation also showed that the interface charge transfer resistance was lowered relative to TiO 2 , facilitating the efficacy of photocatalytic reactivity, where the generation of holes as charge carriers was the rate-limiting step. The novel nano-engineering strategy providing highly active photocatalysis can open new horizons for VL applications. [Display omitted] • Unique d10 and sp/p configurations in its electronic structure, yield high photocatalysis. • Ferroelectric p-block photocatalyst fabrication, by bandgap engineering. • The efficient charge due to electric field in ASO from distorted SiO 4 chain structure. [ABSTRACT FROM AUTHOR]

A convenient direct ink writing porous ceramic preparation strategy incorporating green body strengthening measure was provided. Different hydrogen bond interactions between particles in polar and nonpolar solvents have been successfully applied to regulate the rheological properties of 3D printing ink. Inks with different (NH 4)H 2 PO 4 content were systematically optimized, which exhibited acceptable ambient stability and superior printing behavior. The phosphoric acid generated by decomposition of (NH 4)H 2 PO 4 reacts with silica or oxide layer of silicon nitride to form Si–O–P binder by a pretreatment at low temperature to strengthen the green body. The compressive strength of green body fabricated by ink with 0.2 g/mL (NH 4)H 2 PO 4 was increased by 415%. The Si 2 N 2 O single wall frame structure parts with a compressive strength of 3.33 ± 0.14 MPa under a frame density of 1.14 ± 0.05 g/cm3 were fabricated. The dielectric constants of the developed ceramic parts range from 3.57 to 4.21. A systematic study of design and preparation of ink and quantization of molding parameters provide a reference for in-situ reinforced the ceramic green body of silica, silicon nitride and their composites, as well as fabrication of their corresponding highly porous ceramic components based on the direct ink writing. Image 1 • A strategy for direct ink writing of high-strength Si 2 N 2 O green bodies as well as their ceramic components was provided. • The rheological properties of inks were regulated by the different hydrogen bond interactions between particles in C 10 H 22 O 5 and H 2 O. • The phosphorus elements introduced by (NH 4)H 2 PO 4 aqueous solution were evenly distributed in green body and ceramic part. • The compressive strength of Si 2 N 2 O green body was increased up to 415% due to the strengthening of Si–O–P binder. [ABSTRACT FROM AUTHOR]

Ag x Si y O z has the potential to inhibit the recombination of photoinduced electron hole pairs via an internal electric field induced by asymmetrical Si–O tetrahedral chains. The strength of the [SiO 4 ] tetrahedral produces a very strong internal electric field for Ag 10 Si 4 O 13. Here, a novel and convenient synthetic strategy for nano-Ag 10 Si 4 O 13 based on a sol-gel method is proposed. A small band gap, an internal electric field and a small size ensure good efficiency for nano-Ag 10 Si 4 O 13 during all chemical dynamical processes, including charge excitation, charge separation and charge transfer. [ABSTRACT FROM AUTHOR]

The performance of carbon-based materials as negative electrodes for supercapacitors can be effectively enhanced through the method like increasing the surface area and active sites as well as heteroatoms doping, while the limited capacitance caused by the surface adsorption mechanism restricts the further improvement of capacitance. Herein, we design hollow and porous FeP spheres (H-FeP) in-situ encapsulated into 3D honeycomb-like porous graphitic N, P-codoping carbon (PGNPC) by a unique post-annealing strategy. The post-annealing process acts as an efficient modification strategy in two aspects: the formation of a porous graphitic carbon framework during the catalytic reaction between iron oxide with carbon and the morphology changing from solid to hollow by introducing the Kirkendall diffusion process. With the synergetic effect of introducing hollow FeP into carbon, the N, P-codoping and 3D porous graphitic carbon framework ensure the as-prepared materials with enhanced performance for negative electrodes. Thus, H-FeP@PGNPC materials display outstanding specific capacitance (696 F g−1), high rate capacity and cycling stability. Using multi-shelled Mn 3 O 4 encapsulated in rGO as the positive electrode, the assembled asymmetric supercapacitor exhibits high specific capacitance and energy density with negligible capacity loss (retain 90% after 5000 cycles). [Display omitted] • Novel in-situ encapsulated hollow FeP into N,P-codoped porous graphenic framework obtained through a high-yield process. • The catalytic reaction caused by the post-annealing process provides extra pseudocapacitive contributions. • The porosity and hollow structure of FeP manipulated by Kirkendall effect. • Porous graphenic framework simultaneously acts as the buffer layer and expressway for electrons transport. [ABSTRACT FROM AUTHOR]