No abstract

Microbially induced carbonate precipitation (MICP) is a promising technology for solidifying sandy soil, ground improvement, repairing concrete cracks, and remediation of polluted land. By solidifying sand into soil capable of growing shrubs, MICP can facilitate peak and neutralization of CO2 emissions because each square meter of shrub can absorb 253.1 grams of CO2 per year. In this paper, based on the critical review of the microbial sources of solidified sandy soil, models used to predict the process of sand solidification and factors controlling the MICP process, current problems in microbial sand solidification are analyzed and future research directions, ideas and suggestions for the further study and application of MICP are provided. The following topics are considered worthy of study: (1) MICP methods for evenly distributing CaCO3 deposit; (2) minimizing NH4+ production during MICP; (3) mixed fermentation and interaction of internal and exogenous urea-producing bacteria; (4) MICP technology for field application under harsh conditions; (5) a hybrid solidification method by combining MICP with traditional sand barrier and chemical sand consolidation; and (6) numerical model to simulate the erosion resistance of sand treated by MICP.

Microbial-induced CaCO3 precipitation (MICP) is an innovative and rapidly developing technology for sand solidification. The idea for this research project was built based on the concept of sustainable development and environmental protection. The specific material used for solidification was soluble calcium ions generated by the reaction of limestone waste, a kind of calcium-rich industrial waste from a quarry, and acetic acid. Using Ca(CH3COO)2 (prepared from limestone waste) as a calcium source resulted in a 31.87% lower MICP cost compared to using CaCl2. An unconfined compressive strength (UCS) test was conducted to characterize the macroscopic mechanical properties of bio-cured sand columns. The mineral composition and the microstructure of sand columns were examined by using X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM). After response surface optimization, the optimal conditions for the reaction of limestone and CH3COOH were determined, and the calcium acetate yield was up to 96.81%. The UCS of sand samples treated with limestone/acetic acid was 10.61% higher than that of samples treated with calcium chloride. This research confirmed the feasibility of cheap limestone waste and soluble calcium ions generated by acetic acid as a calcium source, instead of calcium chloride, for solidifying sand columns in the MICP process.

Objective: To observe the clinical benefit of cluster nursing mode in RICU patients with acute exacerbation of Chronic Obstructive Pulmonary Disease (COPD) complicated with RF. Methods: From December 2020 to March 2022, 73 cases of patients with acute COPD and RF admitted to RICU Department of Respiratory Department were selected. According to the order before and after admission to RICU department of respiratory department, patients with inability to communicate due to disease were excluded and divided into two groups. Control group: Adoption of traditional nursing mode; Observation group: Cluster nursing mode was adopted. After nursing, blood gas analysis results and patients' satisfaction scores on nursing work were compared and observed between the two groups. Results: The blood gas analysis results of the observation group were significantly better than the control group, and their evaluation of nursing work was also higher than the control group. Conclusion: In the clinical operation of our department RICU, this cluster nursing mode alleviates the distress perception of patients with COPD acute attack combined with RF, which also alleviates the patients' mood, improves the patients' understanding and satisfaction of nursing work, and thus playing a promoting role in improving the nursery-patient relationship and nursery-patient harmony.