Study on the freezing–thawing deformation of consolidated soils under high pressure

The freezing-thawing deformation behaviors of consolidated soils under high pressure have been investigated in a high-pressure-low-temperature （HPLT） Kq consolidation apparatus with a small strain sensor. The tests cover a variety of frozen soil temperatures ranging from -2℃ to -10 ℃, and a series of applied pressures ranging from 1 MPa to 5 MPa. The test results show that, for the consolidated soils under high pressure, their freezing-thawing deformation was caused by the realignment and the deformation of soil particles, the phase change of water, and the water redistribution in the soil. As for the deformation produced by thermal expansion and contraction,it is about 0.04-0.05 mm, accounting for only about 7%~9% of the total deformation. Taking the freezing-thawing deformation produced by temperature disturbance as a creep deformation, the creep models of the developing soil deformation will be determined by the soil＇s final temperature, i.e., the desired temperature. For the soils under a desired temperature between -2℃ and -5℃, the freezing-thawing de-formation develops according to a non-attenuation creep model; but for the soils with a desired temperature lower than -5℃, a full attenuation creep model is followed. The applied pressure and soil type also have a significant influence on the maximum freezing deformation. Generally, the greater the desired pressure applied, the less the maximum deformation is; and the loess freezing deformation is larger than that of sand.

Fe-N co-doped coral-like hollow carbon shell toward boosting peroxymonosulfate activation for efficient degradation of tetracycline: Singlet oxygen-dominated non-radical pathway

Fe-N co-doped coral-like hollow carbon shell (Fe-N-CS) was synthesized via a simply impregnation-pyrolysis method.The Fe-N-CS showed an excellent ability for activating peroxymonosulfate (PMS),which could degrade about 93.74%tetracycline (20 mg/L) in 12 min.The Fe-N-CS/PMS system exhibited a good anti-interference capacity of various pH,inorganic anions,HA and different water qualities.More importantly,the Fe nanoparticles were anchored uniformly in the carbon layer,effectively limiting the metal leaching.The quenching tests and electron spin resonance (ESR) manifested that non-radical singlet oxygen (1O_(2))was the main reactive oxygen species (ROS) for TC degradation.The mechanism study showed that Fe nanoparticles,defect and graphite N played a key role in activating PMS to produce ROS.Moreover,three probable degradation pathways were proposed by using LC-MS measurements.Generally,this work had a new insight for the synthesis of heterogeneous Fe-N-C catalysts in the advanced oxidation process based on PMS.

Dopamine-triggered one-step functionalization of hollow silica nanospheres for simultaneous lubrication and drug release

Osteoarthritis(OA)has been regarded as a lubrication deficiency related joint disease.Combination of both joint lubrication and drug intervention may provide a promising nonsurgical strategy for treatment of OA.Developing novel and simple approaches to fabricate superlubricating nanoparticles with drug release property is highly required.Herein,dopamine triggered one-step polymerization method was employed to fabricate polydopamine/poly(3-sulfopropyl methacrylate potassium salt)(PDA-PSPMA)conjugate coating on hollow silica(h-SiO_(2))nanosphere surfaces to engineer functional nanoparticles(h-SiO_(2)/PDA-PSPMA).The as-prepared h-SiO_(2)/PDA-PSPMA exhibits excellent aqueous lubrication performance on biomaterial substrates as well as natural bovine articular cartilage based on hydration effect of negatively charged PDA-PSPMA coating and"rolling"effect of h-SiO_(2)nanospheres.In vitro drug loading-release experiments demonstrate that PDA-PSPMA coating functionalized h-SiO_(2)nanospheres show high drug-loading and sustained-release capability of an anti-inflammatory drug,diclofenac sodium(DS).Such h-SiO_(2)/PDA-PSPMA nanospheres can be potentially used as a synergistic therapy agent for OA treatment combining by simultaneous joint lubrication anddrugrelease.

Peroxymonosulfate activation by Fe-N-S co-doped tremella-like carbocatalyst for degradation of bisphenol A: Synergistic effect of pyridine N, Fe-Nx, thiophene S

Bisphenol A(BPA)has received increasing attention due to its long-term industrial application and persistence in environmental pollution.Iron-based carbon catalyst activation of peroxymonosulfate(PMS)shows a good prospect for effective elimination of recalcitrant contaminants in water.Herein,considering the problem about the leaching of iron ions and the optimization of heteroatoms doping,the iron,nitrogen and sulfur co-doped tremellalike carbon catalyst(Fe-NS@C)was rationally designed using very little iron,S-C_(3)N_(4) and low-cost chitosan(CS)via the impregnation-calcination method.The as-prepared Fe-NS@C exhibited excellent performance for complete removal of BPA(20 mg/L)by activating PMS with the high kinetic constant(1.492 min^(−1))in 15 min.Besides,the Fe-NS@C/PMS system not only possessed wide pH adaptation and high resistance to environmental interference,but also maintained an excellent degradation efficiency on different pollutants.Impressively,increased S-C_(3)N_(4) doping amount modulated the contents of different N species in Fe-NS@C,and the catalytic activity of Fe-NS@C-1-x was visibly enhanced with increasing SC_(3)N_(4) contents,verifying pyridine N and Fe-Nx as main active sites in the system.Meanwhile,thiophene sulfur(C-S-C)as active sites played an auxiliary role.Furthermore,quenching experiment,EPR analysis and electrochemical test proved that surface-bound radicals(·OH and SO_(4)^(·−))and non-radical pathways worked in the BPA degradation(the former played a dominant role).Finally,possible BPA degradation route were proposed.This work provided a promising way to synthesize the novel Fe,N and S co-doping carbon catalyst for degrading organic pollutants with low metal leaching and high catalytic ability.

Tetracycline removal via adsorption and metal-free catalysis with 3D macroscopic N-doped porous carbon nanosheets:Non-radical mechanism and degradation pathway

Recently,metal-based carbon materials have been verified to be an effective persulfate activator,but secondary pollution caused by metal leaching is inevitable.Hence,a green metalfree 3D macroscopic N-doped porous carbon nanosheets(NPCN)was synthesized successfully.The obtained NPCN showed high adsorption capacity of tetracycline(TC)and excellent persulfate(PS)activation ability,especially when calcined at 700℃(NPCN-700).The maximum adsorption capacity of NPCN-700 was 121.51 mg/g by H-bonds interactions.Moreover,the adsorption process followed pseudo-second-order kinetics model and Langmuir adsorption isotherm.The large specific surface area(365.27 mg/g)and hierarchical porous structure of NPCN-700 reduced the mass transfer resistance and increased the adsorption capacity.About 96.39%of TC was removed after adding PS.The effective adsorption of the catalyst greatly shortened the time for the target organic molecules to migrate to the catalyst.Moreover,the NPCN-700 demonstrated high reusability with the TC removal rate of 80.23%after 4 cycles.Quenching experiment and electron paramagnetic resonance(EPR)test confirmed the non-radical mechanism dominated by ^(1)O_(2).More importantly,the C=O groups,defects and Graphitic N acted as active sites to generate ^(1)O_(2).Correspondingly,electrochemical measurement revealed the direct electron transfer pathway of TC degradation.Finally,multiple degradation intermediates were recognized by the LC-MS measurement and three possible degradation pathways were proposed.Overall,the prepared NPCN had excellent application prospects for removal of antibiotics due to its remarkable adsorption and catalytic degradation capabilities.