Linwei Yu

Intellectual demands of learning outcomes in the intended curriculum have always been a concern across the field of science education. In particular, the representation of those learning outcomes stipulated by the intended curriculum in science textbooks has become a big issue for both science curriculum studies and science teaching practice. To address this issue, the concepts of semantic gravity (SG) and semantic density (SD), as part of the dimension of Semantics from Legitimation Code Theory (LCT), were employed in this study with the purpose of examining the degrees of abstraction and complexity of chemical knowledge under the topic “common substances” in four series of chemistry textbooks, which were compiled in compliance with the national chemistry curriculum of the compulsory education (Grades 1–9) in China. Based on the principles of LCT (Semantics), a new scheme for differentiating the strengths of SG and SD was developed in the current study to analyze the representation of 34 knowledge points in the four series of chemistry textbooks. Results show that these knowledge points are embodied with less complexity and avoid more abstraction in the four series of chemistry textbooks. Specifically, it was found that the overwhelming majority of the knowledge points are represented with strong semantic gravity and weak semantic density. Uniqueness was also identified with individual series of chemistry textbooks. The implications of the results of this study are discussed for the effective representation of science (chemistry) knowledge in textbooks.

The adsorption method is widely used in wastewater treatment because of its advantages of simple operation, high efficiency, no secondary pollution, and reusability. In the process of adsorption, the recovery of adsorbents determines their economic feasibility and suitability for large-scale practical applications, so it is of great significance to develop new functional adsorbents with self-floating separation characteristics to replace traditional adsorbents. Hollow glass microsphere (HGM) is a kind of hollow closed sphere, which has the advantages of low density, stable chemical properties, reusable, excellent compression resistance, etc. Due to the unique structure and chemical properties of HGM, it has extremely high potential value in the field of wastewater treatment, and is an ideal carrier for preparing adsorbents with self-floating adsorbents. In this paper, the modification of HGM, the regeneration of adsorbents, the factors affecting the adsorption performance and challenges are reviewed. It is found that most of the existing modification methods of HGM are surface chemical modification, and the adsorption effect and regeneration are significant, but the adsorption effect is greatly affected by the change of pH. This review aims to provide a theoretical basis for the application of HGM in wastewater treatment, and for relevant researchers to develop adsorbent with HGM as the main body, clarify ideas, and explore the potential of developing HGM into practice for large-scale wastewater treatment.