As a major component of greenhouse gases, excessive carbon dioxide (CO2) in the atmosphere can affect human health and ecosystems. Therefore, the capture and transformation of CO2 has attracted extensive attention in academic circles in recent years. Direct air capture (DAC) of CO2 is a technology developed in recent years that can capture and collect CO2 directly from the ambient air, which is a potential negative CO2 emission technology. Currently, DAC technology is being promoted worldwide. Therefore, given the lack of a timely review of the latest developments in DAC technology, an appropriate and timely summary of this technology and a comprehensive understanding of it is necessary. In this paper, we review the research progress of adsorbent materials for directly capturing CO2 from ambient air in recent years, including liquidbased absorbent, solid adsorbent, and moisture-swing adsorbent. How their chemical composition, structure, morphology, modification method affects their performance and long-term use is thoroughly discussed. In addition to efficient CO2 adsorption properties, designing low-cost sustainable materials is critical, especially for practical applications. Therefore, the technical and economic evaluation of CO2 adsorbents directly capturing from ambient air is reviewed. This review is of great significance for researchers to fully understand the development status and future trends of direct capture of CO2 from ambient air.

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Steel slag is the main by‐product during the steel manufacturing process, with the characteristics of large output and low utilization rate. Since the high content of calcium oxide in steel slag, it is often used for CO2 capture. In this paper, progress on the development of steel slag for fixing CO2 is reviewed. This review is organized according to the carbonation type of steel slag, including direct carbonation and indirect carbonation. For direct carbonation, it is introduced from two parts: aqueous carbonation and gas‐solid carbonation. For indirect carbonation, it is summarized according to the extracting agent. The carbonation condition and capacity will be carefully discussed. Besides, the techno‐economic assessments of using steel slag for CO2 capture are discussed. This paper will provide an overview of the steel slag using for CO2 sequestration available and valuable suggestions for future study.

IntroductionPrimary postoperative ileus is one of the principal factors affecting in-hospital recovery after colorectal surgery. Research on the relationship between anaesthetic depth and perioperative outcomes has been attracting growing attention. However, the impact of anaesthetic depth on the recovery of gastrointestinal function after surgery is unclear. We aimed to conduct a single-centre, prospective, randomised, controlled trial to explore the effect of anaesthetic depth on primary postoperative ileus after laparoscopic colorectal surgery.Methods and analysisIn this single-centre, prospective, patient-blinded and assessor-blinded, parallel, randomised, controlled trial, a total of 854 American Society of Anesthesiologists physical status I-III patients, aged between 18 and 65 years and scheduled for laparoscopic colorectal surgery lasting ≥2 hours, will be randomly assigned to deep anaesthesia group (Bispectral Index (BIS) 30–40) or light anaesthesia group (BIS 45–55). The primary outcome is primary postoperative ileus during the hospital stay. Secondary outcomes were time to gastrointestinal function recovery, another defined postoperative ileus, 15-item quality of recovery score, length of postoperative stay, postoperative 30-day complications and serum concentrations of intestinal fatty acid-binding protein at 6 hours after surgery.Ethics and disseminationThe protocol was approved by Medical Ethics Committee of Nanfang Hospital, Southern Medical University (Approval number: NFEC-2018–107) prior to recruitment. All participants will provide written informed consent before randomisation. Findings of the trial will be disseminated through peer-reviewed journals and scientific conferences.Trial registration numberChiCTR1800018725.