Development and validation of a specialized system for self-tapping medical bone screw testing.

A specialized system for accurate self-tapping medical bone screw testing is developed, fully meeting the requirements of ASTM F543-A4 (YY/T 1505-2016). The onset of self-tap is identified automatically according to a change in the slope of the torque curve. Precise load control is applied to determine the self-tapping force accurately. A simple mechanical platform is embedded to ensure the automatic axial alignment of a tested screw with the pilot hole in a test block. In addition, comparative experiments are conducted on different self-tapping screws to verify the system's effectiveness. By the automatic identification and alignment method, both torque curves and axial force curves for each screw exhibit significant consistency. The self-tapping time point derived from the torque curve agrees well with the turning point of the axial displacement curve. The determined self-tapping forces' mean values and standard deviations are both small, which are proved to be effective and accurate in the insertion tests. This work contributes to improving the standard test method for accurate determination of the self-tapping performance of medical bone screws.

Treatment of industrial ferric sludge through a facile acid-assisted hydrothermal reaction: Focusing on dry mass reduction and hydrochar recyclability performance.

Large amounts of Fenton sludge and waste activated sludge (WAS) are mixed as ferric sludge (FS) in most industrial wastewater treatment plants. The treatment of such waste represents a challenge and quantity-dependent cost, so that a reliable way for FS waste reduction is required. In this study, we develop a facile acid-assisted hydrothermal treatment (HT) for the cost-efficient treatment of hazardous FS waste. Sulfuric acid was dosed at 0.25 mL/g dry solid (DS) to the HT process, which significantly increased the total solid mass reduction (TMR) by 25.1 % and dry mass reduction (DMR) by 104.4 %. The participation of sulfuric acid during the HT process changed the HT reaction pathway from dehydration to demethylation based on the analysis of the derivative thermogravimetric and Van Krevelen diagram. The addition of sulfuric acid improved the release of Fe from FS by 52.9 %, which contributed to the DMR. During the acid-assisted HT, Fe(III) was effectively reduced to Fe(II) within the produced hydrochar, which can be recycled for the Fenton reaction during the degradation of actual industrial wastewater such as pharmaceutical wastewater. Moreover, Sulfuric acid facilitated the generation of sulfonated hydrochar, which was efficient as an adsorbent for the complete removal of some metals such as Cu(II) - cation metal (98.8 %) and Cr(VI) - anion metal (99.9 %). This study firstly provides a novel and reliable approach for hazardous FS reduction and pointed out the recycling of hydrochar as the supplement for the Fenton reaction and adsorbents for some hazardous heavy metals.

Responses of soil fertility and microbiomes of atrazine contaminated soil to remediation by hydrochar and persulfate.

Peroxydisulfate (PDS) is widely used in field-scale remediation of organically polluted soil, yet PDS is detrimental to the soil microbiome. In this work, sludge-derived hydrochar was used to alleviate the oxidative damage of PDS to the soil ecosystem and simultaneously improve atrazine (ATZ) degradation. Response surfaces showed that ATZ degradation was enhanced with an increased dosage of PDS (regression slope of 24.09) and hydrochar (regression slope of 4.19). In contrast, bacterial abundance was negatively related to PDS dosage but positively to hydrochar dosage. At the optimum dosage of PDS (2.21% dry weight of soil) and hydrochar (5% dry weight of soil), ATZ degradation reached 95.31%, and bacterial abundance recovered to 7.72 log gene copy number g-1 soil (versus 8.44 in raw soil). Hydrochar alleviated the negative impacts of PDS on soil fertility such as urease activity. High PDS dosages (3% dry weight of soil) facilitated the proliferation of Halomonas, while moderate dosages (1.5% dry weight of soil) stimulated Alicyclobacillus. Hydrochar facilitated the growth of functional genera like Comamonas, Cloacibacterium, and Terrabacter. ATZ degradation pathway was positively correlated with Bacillus and nitrogen metabolism pathway. Hydrochar mediated intracellular reactive oxidative species scavenger reactions in catalase activity, allowing microbial survival under harsh oxidative conditions due to PDS addition.

Production of high optical purity l-lactic acid from waste activated sludge by supplementing carbohydrate: effect of temperature and pretreatment time.

It has been widely accepted that the most environmentally beneficial way to treat waste activated sludge (WAS), the byproduct of municipal wastewater treatment plant, is to recover the valuable organic acid. However, the bio-conversion of lactic acid, one of the high added-value chemical, is seldom reported from WAS fermentation. In this paper, l-lactic acid was observed dominant in the WAS fermentation liquid with carbohydrate addition at ambient temperature. Furthermore, the effect of temperature on l-lactic acid and d-lactic acid production was fully discussed: two isomers were rapidly produced and consumed up in one day at mesophilic condition; and almost optically pure l-lactic acid was generated at thermophilic condition, yet time-consuming with yield of l-lactic acid enhancing by 52.9% compared to that at ambient temperature. The study mechanism showed that mesophilic condition was optimal for both production and consumption of l-lactic acid and d-lactic acid, while consumption of l-lactic acid and production of d-lactic acid were severely inhibited at thermophilic condition. Therefore, by maintaining thermophilic for 4 h in advance and subsequently fermenting mesophilic for 34 h, the concentration of l-lactic acid with optical activity of 98.3% was improved to 16.6 ± 0.5 g COD/L at a high specific efficiency of 0.6097/d.