Effects of the chromium content on anaerobic fermentation of chrome shaving collagen and rice straw juice.

This thesis investigated the effects of different chromium contents on the gas production characteristics of anaerobic fermentation by mixing the collagen solution obtained from the hydrolysis of chromium tannin chips by alkali-enzyme combination with rice stalk hydrolysate and the changes of system pH, VFA concentration, SCOD concentration, ammonia nitrogen concentration, and chromium concentration during anaerobic fermentation. The experimental results show that the highest total gas production and cumulative methane production are 1531.0 mL/gVS and 761.2 mL/gVS, respectively, with a Cr content of 5 mg/L, and the methane content reaches 49.7%. The best SCOD removal rate is 54.54% at a C/N ratio of 20:1. The increase in SCOD concentration is decreased with increasing chromium content, but there is no significant change in ammonia nitrogen concentration. The highest rate of SCOD degradation is achieved with a chromium content of 5 mg/L. The results of this thesis provide data support and theoretical guidance for the resource recovery of chromium leather shavings.

Effects of potassium ferrate-walnut shell pretreatment on dehydration performance of residual sludge.

Sludge dehydration is not only the first process of sludge reduction but also difficult for sludge treatment and disposal, while the high moisture content of sludge would also limit its resource utilization. In this paper, the residual sludge was treated by the strong oxidizing property of potassium ferrate (PF), and walnut shells were used as a skeleton builder to obtain the recycling dehydrated sludge. It also provides a new solution for the poor stability of PF in the treatment of sludge and waste walnut shells. The experiment results showed that the optimum dosage of PF and walnut shell was 60 mg/gDS and 0.8 g/gDS, respectively, and the water content of the combined PF and walnut shell treatment decreased by 5.2% and 3.7% compared to that of PF conditioning alone and walnut shell conditioning alone, respectively. In addition, scanning electron microscopy and three-dimensional fluorescence spectroscopy revealed a large number of cracks on the sludge surface after the combined treatment, and the sludge floc structure became more loose and dispersed, and the hydrophobic substances humic acid and fulvic acid increased, indicating that the dewatering performance of the sludge was effectively improved, further confirming that the combined PF and walnut shells treatment provides a new idea and method for sludge dewatering.

The preparation and properties of iron-walnut shell powder microelectrolytic spherical fillers.

In order to solve the issues of caking, loss, and effluent color reversion in the application of traditional microelectrolysis, the iron-walnut shell powder microelectrolytic spherical filler was developed in this paper. The filler was prepared by walnut shell powder, iron powder, sodium silicate, and sodium humate activated by ZnCl2 as raw materials and calcined at high temperature. The effects of the mass ratios of Fe to walnut shell powder, sodium silicate content, sodium humate content, calcination temperature, and time on the removal rate of methylene blue by the spherical fillers were investigated, so as to determine the optimal preparation conditions of the spherical fillers. The pore-forming structure and the composition of the spherical fillers were also analyzed by an X-ray diffractometer (XRD), a scanning electron microscope (SEM), and an energy spectrometer (EDS). The results show that the optimal preparation conditions for the spherical fillers of 5 mm are as follows: the mass ratio of iron powder to walnut shell powder treated by 15% ZnCl2 is 1:1, sodium silicate is 15%, sodium humate is 20%, the calcination temperature is 800 °C, and the calcination time is 3 h. Compared with the conventional microelectrolysis, the removal rate of methylene blue by the spherical fillers can finally reach the same level as it did, and the phenomena of the filler hardening and clogging can be avoided.

Effect of Iron-Carbon Micro-Electrolysis-Fenton on the Dewatering Performance of Sludge.

In this paper, combined with iron-carbon micro-electrolysis-Fenton method, the sludge was adjusted, and the cracking performance and dewatering performance of the sludge were studied. Single factor experiments show that when the amount of iron powder is 1.2 g/L, the reaction time is 45 min, H2 O 2When the dosage was 4.2 g/L, the protein and polysaccharide content in the sludge decreased by 46.8 and 20.6, respectively. Compared with the original sludge %. Compared with the original sludge, the COD of the supernatant of the solution increased by 10.1%. The minimum moisture content of the treated sludge cake was 69%, and the SRF value was significantly reduced.The lowest value is 2.687×10 12 m/kg. During the micro-electric dust removal sludge, the Fe 2+can form a Fenton reagent with H2 O 2, thereby reducing the amount of additional iron powder that needs to be added in the conventional Fenton reaction. Three-dimensional fluorescence spectroscopy analysis showed that the humic acid and fulvic acid in the supernatant of the iron-carbon micro-electrolysis-Fenton conditioning solution increased more than after single electrolysis, indicating that the dehydration performance of the sludge was better.The Fenton reagent is formed , thereby reducing the amount of iron powder that needs to be added extra in the conventional Fenton reaction.

Acute effect of engineered thermoplastic polyurethane elastomer knockoff running footwear on foot loading and comfort during heel-to-toe running.

BACKGROUND: Better midsole materials and comfort have been incorporated into more expensive shoes and are popular with runners. Consequently, knockoff running shoes are currently widely distributed in the Chinese market and and cost only 30%-50% of the total price of genuine branded products. RESEARCH QUESTION: Uncertainty exists concerning the beneficial effects of advanced shoe material application in decreasing foot loading or impact force during running. Additionally, using comfort as a criterion to identify genuine branded running shoes may exclude brand factor. METHODS: Fifteen healthy male volunteers were asked to perform two different tests, including running and a comfort evaluation. Each participant was asked to identify which footwear was the Adidas brand shoe based on their perception of comfort. RESULTS: Time to the first peak of the vertical ground reaction force occurred significantly later when subjects wore the genuine branded shoe compared to knockoff shoe 1 (p = 0.003) and knockoff shoe 2 (p = 0.015) footwea. The genuine branded shoe (p = 0.005) and knockoff shoe 1 (p = 0.029) were significantly more comfortable compared to the knockoff shoe 2. Only four subjects selected the genuine branded shoe, whereas six subjects selected both the genuine branded shoe and knockoff shoe 1. SIGNIFICANCE: Knockoff running footwear significantly increases impact loading compared to the genuine branded product, thereby posing greater risk of running injury.

Effect of Running Speed and Midsole Type on Foot Loading in Heel-Toe Running.

The purpose of this study was to explore the immediate effects of running speed and midsole type on foot loading during heel-toe running. Fifteen healthy male college students were required to complete 3 running trials on an indoor 45-m tartan runway at 4 different speeds (3, 4, 5, and 6 m/s) using 2 different running footwear types (engineering thermoplastic polyurethane elastomer, polyurethane elastomer; and ethylene vinyl acetate, vinyl acetate). The ground reaction force and plantar pressure data were quantified. Significant speed effects were detected both in ground reaction force and plantar pressure-related data (P < .05). Vertical average loading rate was significantly less, and time to first peak occurred later for the polyurethane elastomer compared with vinyl acetate footwear (P < .05). The peak pressure of the heel, medial forefoot, central forefoot, lateral forefoot, and big toe was significantly less when subjects wore a polyurethane elastomer than vinyl acetate footwear (P < .05). Overall, our results suggested that, compared with the vinyl acetate footwear, the special polyurethane elastomer footwear that is adhered with thousands of polyurethane elastomer granules was effective at reducing the mechanical impact on the foot.

Spatial and daily variations of nitrous oxide emissions from biological reactors in a full-scale activated sludge anoxic/oxic process.

Nitrous oxide (N2O) is an important greenhouse gas that can be emitted from wastewater treatment plants (WWTPs). Such emissions are reportedly process specific and related to operational parameters. This study was conducted to clarify spatial and daily variations of N2O in a full-scale activated sludge anoxic/oxic process that consisted of an anoxic tank and three oxic tanks (oxic-1, oxic-2 and oxic-3), all of which except the final sedimentation tank were fully covered. Higher dissolved N2O (D-N2O) loading and gaseous N2O (G-N2O) emissions were observed for oxic-3 than for the anoxic, oxic-1, and oxic-2 tanks, implying that there was higher N2O production potential via nitrification in the latter stage of the oxic tank. Moreover, the sudden decrease in dissolved oxygen concentration after the peak was found to lead to abrupt production of D-N2O at oxic-3 in the anoxic/oxic process. The increases in AOB amoA, AOB nirK and the following AOB norB gene transcripts at the end of the oxic-2 tank suggested that nitrifier denitrification occurred to produce N2O under low dissolved oxygen conditions when the N2O peak was observed. Additionally, the much lower transcription levels of the two nosZ genes suggested lower N2O consumption. The N2O emission factors ranged from 0.087% to 0.302%, and lower N2O emission factors were observed during summer.

Preparation of chrome-tanned leather shaving-based hierarchical porous carbon and its capacitance properties.

Based on the complexes formed by the original Cr(iii) in chrome-tanned leather shavings and the carboxyl groups in collagen as raw materials, a chromium oxide-carbon composite material was formed by the high-temperature carbonization of chromium-tanned leather shavings, followed by the leaching of chrome oxide and activation by KOH. By this method, the hierarchical porous carbon with a high surface area doped with oxygen and nitrogen was prepared. The forming process of the hierarchical porous structure is discussed in detail. Through adjusting the mass ratio of KOH to carbon during the activation process, with a mass ratio of 2, the chromium-tanned leather shavings-based hierarchical porous carbon (called CTSHPC-2) was prepared with an optimal specific surface area (3211 m2 g-1) and a large volume ratio of mesopores to macropores (61.9%) as well as abundant oxygen (13.92 at%) and nitrogen (3.58 at%) functional groups. The results showed that CTSHPC-2 obtained a high specific capacitance of 335.5 F g-1 at a current density of 0.5 A g-1. In addition, it had higher rate performance, low resistance, and better cycle stability. Even when the current density is 10 A g-1 over 5000 cycles, the specific capacity retention rate is 93.5%. Therefore, CTSHPC-2 is a promising electrode material for supercapacitors.

Sakura-based activated carbon preparation and its performance in supercapacitor applications.

3D porous carbonaceous materials were prepared by combining pre-carbonization and KOH activation with sakura petals as raw materials. The prepared porous sakura carbon (SAC-4) exhibits a high specific surface area, a suitable pore size distribution, a low proportion of oxygen-rich groups and N functional groups, and a partially graphitized phase, which are very beneficial for the electrochemical performance of the material as a supercapacitor electrode. In the activation step, when the mass ratio of KOH to sakura carbon (SC) is 4, a supercapacitor is prepared. A maximal specific capacitance of 265.8 F g-1 is obtained when the current density is 0.2 A g-1. When the current density is 1 A g-1, after 2000 cycles in succession, the capacitance retention rate is excellent and the cycling stability can reach as high as 90.2%. The obtained results indicate that porous carbon prepared with sakura blossom as the raw material is an effective and environmentally friendly electrode material for energy storage.