The structure and chemical composition of cell walls play a vital role in the bioconversion and utilization of plants. In the present study, the cell wall structure and chemical composition of pith and rind from sunflower stalks were compared and correlated to their nanofibrillation efficiency with ultrasonic treatment. Mild chemical pretreatment using 1% or 4% NaOH without any bleaching process were applied prior to ultrasonication nanofibrillation. Significant structural and chemical differences were demonstrated between the pith and rind, with the former exhibiting a much lower lignin and hemicellulose contents, higher pectin, much looser cell structure and higher cell wall porosity than the latter. Alkaline treatment alone was sufficient to eliminate most of the hemicellulose and pectin from stalk pith, whereas only partial removal of hemicellulose and lignin was achieved for the woody rind part. After 30 min of ultrasonic treatment, the stalk pith exhibited fully defibrillated fibrils with a continuous and entangled micro/nanofibrillated network, whereas numerous micron-sized fiber and fragments remained for the rind. The results indicated that stalk pith is less recalcitrant and easier to be fibrillated with ultrasonication than rind, which must be correlated to their distinct differences in both structure and chemical composition.

The utilization of biogas slurry is critical for the sustainable development of animal husbandry. Biomass carbon adsorption is a feasible method for the recycling of nutrients from biogas slurry. However, research on the co-adsorption of ammonia nitrogen and phosphate is scarce. Herein, soybean straw was utilized as the raw material to prepare Ca²⁺-modified biochar (CaSSB), which was investigated for its ammonia nitrogen and phosphate adsorption mechanisms. Compared with natural biochar (SSB), CaSSB possesses a high H/C ratio, larger surface area, high porosity and various functional groups. Ca²⁺-modified soybean straw biochar exhibited excellent adsorption performance for NH₄⁺–N (103.18 mg/g) and PO₄³⁻−P (9.75 mg/g) at pH = 6, using an adsorbent dosage of 2 g/L. The experimental adsorption data of ammonia nitrogen by CaSSB corresponded to pseudo-second-order kinetics and the Langmuir isotherm model, suggesting that the adsorption process was homogeneous and that electrostatic attraction might be the primary adsorption mechanism. Meanwhile, the adsorption of phosphate conformed to pseudo-second-order kinetics and the Langmuir–Freundlich model, whose mechanism might be attributed to ligand exchange and chemical precipitation. These results reveal the potential of CaSSBs as a cost-effective, efficient adsorbent for the recovery of ammonium and phosphate from biogas slurry.

Solar interfacial evaporation, featuring no extra energy need and low equipment demand, offers a promising off‐grid desalination solution to alleviate global freshwater shortage. However, solar evaporators typically rely on internal pores for water transport that impedes vapor escape. In this work, exploiting a two‐phase structure and directional arrangement of bamboo, a bamboo fiber aggregation (BFA)‐based broom‐like solar evaporator with open fibrous gaps for water transport and vapor diffusion is developed. The polypyrrole‐coated BFA (PPy‐BFA) evaporator exhibits a water evaporation rate of 3.3 kg m ⁻² h ⁻¹ with an efficiency of 146.7% under 1 sun. This value is 2.6 times higher than that of PPy‐coated natural bamboo and superior to most of the previously reported bamboo‐based evaporators. These low‐tortuosity fiber gaps enable rapid water transport while providing extensive air–liquid interfaces that effectively promote vapor diffusion and harness heat from the environment. Open‐channel configuration has a lower surface temperature and more uniform vapor distribution than that of the internal‐channel one, preventing the formation of high‐humidity zones. Moreover, PPy‐BFA also demonstrates excellent salt tolerance performance, maintaining a stable evaporation rate of 2.3 kg m ⁻² h ⁻¹ for 20% NaCl solution. This work offers important insights into the configuration design of solar evaporators and provides a low‐cost choice for off‐grid desalination.