## 3 Results and Discussion
### Handmade Paper Characterization  
#### 3.2.1 Morphological and Structural Analysis  
A comprehensive review of the extant literature reveals a significant paucity of research specifically addressing cellulose-barite composite systems, despite the growing body of knowledge on related cellulose-based composites, thus presenting a compelling opportunity for novel investigations in this domain. For instance, in [86], the authors investigated barium sulfate/regenerated cellulose composite fibers and their resilience to X-ray radiation. They observed that the X-ray attenuation coefficient of the sample increased as the barium sulfate content rose, eventually reaching a lead equivalent dose of 0.1 mmPb. Furthermore, several recent patents detail methodologies for fabricating polymer-based [87] and cellulose-based [88] (not excluding other materials) fibrous composites incorporating barium sulfate for various applications, including filters, radiation shielding, and adsorbents, among others. This study aimed to produce paper samples with maximum mineral filler content to reduce the demand for cellulose resources and lower production costs. In our experiments, the maximum mineral filler content was set at 40% of the total pulp mass, a ratio applied for sample casting and subsequent analysis. The SEM images (Figure 9) reveal a unique structure in the molded alkali-treated cellulose/barite and bleached-treated/barite composites. This structure is characterized by a mesh of cellulose fibers with embedded barite particles. The flattened appearance of the fibers, a feature attributed to the structure of the initial raw material (grass clippings), underscores the potential for further flattening during chemical-thermal treatment and sheet molding because of the thinness of the cell walls [89]. Figure 9: SEM micrographs and elemental analysis of ATc/barite and BC/barite paper. Barium sulfate (BaSO4), commonly referred to as barite, exhibits elongated near-oval crystal shapes, as illustrated in Figure S3. These crystals feature prominent crystalline facets and well-defined edges, with a smooth surface devoid of visible defects and pores. The average crystal size measures 1.05 microns. Based on the results of EDS analysis, it was observed that the carbon content in two paper samples amounts to 40.12% and 36.1% by weight, while oxygen constitutes 42.57% and 49.00% by weight, respectively. The content of silicon, calcium, and magnesium is comparable to the levels found in the original samples of cellulose obtained through alkaline treatment and bleaching (refer to Figure 5). However, the most crucial parameter, as highlighted by the authors, is the barium content, serving as an indicator of the degree of mineral filler retention. It was demonstrated that the barium content in the handmade paper derived from alkali-treated cellulose is 5.92%, whereas in the bleached cellulose paper, it rises to 14.48% by weight. The lower filler content observed in the alkali-treated cellulose/barite is evident in the SEM images. The authors hypothesize that the increased retention of mineral filler in bleached cellulose/barite is attributed to fibrillation, characterized by the formation of finer cellulose fibrils. This finer fibrillation facilitates greater retention of barite particles. As demonstrated earlier (see Figure 5), the supplementary bleaching procedure induces more pronounced surface degradation of cellulose fibers by removing lignin and amorphous cellulose. Consequently, the surface exhibits a more developed relief structure, enhancing the adhesion of barite particles to the cellulose fiber surface. Furthermore, SEM examination of the cross-sections of the alkali-treated cellulose/barite and bleached cellulose/barite samples revealed distinct differences. In the case of bleached cellulose, denser paper was formed, attributed to superior filler retention. The paper web exhibited a dense, homogeneous structure, positively impacting its strength characteristics.