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Phloridzin is a phenolic acid associated with the genus Malus (Mill.) that causes apple replant disease. The removal of phloridzin is of great significance to alleviate this condition, and hence biochar was investigated for this purpose. The goal of this study was to improve the adsorption capacity of biochar for phloridzin by chemical modification. Biochar from apple branches and biochar modified with chitosan to were characterized by elemental analysis, Brunauer Emmett Teller analysis, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. Batch adsorption experiments were employed to select the optimal biochar dosage and adsorption time. The results showed that biochar treated for 24 h at 6 g L−1 achieved best adsorption properties and that the chitosan-modified biochar provided a higher adsorption capacity than the unmodified material. The influence of pH upon the adsorption was studied and the results were fitted with isotherm and kinetic equations. The results showed that adsorption process corresponds to a Langmuir isotherm and pseudo-second-order kinetics. The qmax of the biochar was increased from 15.93 to 28.96 mg g−1 by modification with chitosan. The pH was shown to play an important role in the adsorption process. The adsorption of phloridzin to biochar was demonstrated to be a single-layer multiple component adsorption process based on chemisorption. This study provides a theoretical basis to alleviate apple replant disease. [ABSTRACT FROM AUTHOR]

To improve the utilization of fertilizer and water resources at the same time, a new slow-release PK compound fertilizer (SRCF) with the function of water retention was prepared. Element analysis results showed that the product contained 20.46% potassium (shown by K2O) and 15.45% phosphorus (shown by P2O5), which were trapped in the matrix of carboxymethylcellulose-graft-poly(acrylic acid-co-itaconic acid) superabsorbent polymer. Major factors affecting the water absorbency of SRCF such as weight ratio of itaconic acid (IA) to acrylic acid (AA), contents of crosslinker, K2HPO4, and carboxymethylcellulose (CMC) were investigated and optimized. The water absorbency of the product was 130 times its own weight if it was allowed to swell in tap water at room temperature for 1 h. Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric/Differential thermal analysis (TG/DTA) confirmed that AA and IA monomers were graft-copolymerized onto CMC backbone and presented the improved thermal stability. The water evaporation of the fertilizer-containing superabsorbents, as well as their nutrients release in sandy soil was carried out, and a possible slow-release mechanism was proposed. Additionally, compressive modulus measurements revealed that the introduction of CMC could improve the mechanical properties of the superabsorbents. These studies showed that the product with good slow-release and water retention properties, being economical and environment-friendly, could be expected to have wide potential applications in modern agriculture and horticulture. [ABSTRACT FROM AUTHOR]