The slow release urea fertilizer was prepared by the boric acid crosslinked starch/polyvinyl alcohol (SPB) matrix as biodegradable carrier material. Using a two level factorial design of experiment, a comprehensive understanding of the concentration of boric acid, reaction time and heating temperature in the preparation of SPB matrix was obtained. The swelling ratio, release profile of urea in water, and crushing strength were selected as the response. The interaction between the variables and response was analyzed using the ANOVA model. The system was confirmed using the constant determination, R2 with values above 0.99. The high concentration of boric acid with a prolonged reaction time at high temperature gave relative good results of swelling ratio, dissolution rate of urea and crushing strength. In the 28-day soil incubation experiment, the retention of exchangeable ammonium ion ${\rm{(NH}}_4^ + )$ was significant higher in SPB urea as compared to pure urea. There was a potential for SPB matrix to improve nitrogen efficiency by increasing the accumulation of exchangeable ${\rm{NH}}_4^ + $ and decreasing the dissolution rate of urea in the flooded condition.

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The increasing number of carbon fibers reinforced polymer (CFRP) waste disposed of in landfills is creating environmental concerns due to the potential release of toxic by-products and the need for recycling. This research work investigates the influence of atmosphere (single and combination of nitrogen and oxygen) and heating rate (5 and 10°C min −1 ) on the thermal decomposition of CFRP to recover the reclaimed-cf The samples were heated up to 420°C in a nitrogen atmosphere followed by heating in the oxygen atmosphere from 420°C until the final heating temperature at different heating rates. The thermal decomposition behavior of the CFRP waste was compared by thermogravimetric analysis (TGA). Morphological, chemical and structural analysis of reclaimed-CF was performed using SEM, FT-IR and Raman spectroscopy respectively. A nitrogen atmosphere was significance at the early temperature (<420°C) to decompose smaller molecules of epoxy resin components, while oxygen atmosphere is needed to achieve a complete separation of reclaimed-CF from their matrix. Thermal decomposition at lower heating rate (5°C min −1 ) was found efficiently to eliminate the complex epoxy resin and retain the structure of reclaimed-cf The particular thermal decomposition technique that leads to a lower final heating temperature (540°C) is present to recover valuable reclaimed-CF from complex CFRP industrial waste.

This paper utilized urea functionalized multiwalled carbon nanotubes fertilizer as plant nutrition for rice to understand fully their mechanism of interaction. Surface modification of multiwalled carbon nanotubes was treated by nitric acid at different reflux times. The individual and interaction effects between the design factors of functionalized multiwalled carbon nanotube amount and functionalization reflux time with the corresponding responses of nitrogen uptake and nitrogen use efficiency were structured via the Response Surface Methodology based on five-level central composite design. The urea functionalized multiwalled carbon nanotubes fertilizer with optimized 0.5 weight% functionalized multiwalled carbon nanotubes treated at 21 h of reflux time achieve tremendous nitrogen uptake at 1180 mg/pot and NUE up to 96%. The FT-IR results confirm the formation of acidic functional groups of functionalized MWCNTs and UF-MWCNTs. The morphological observation of transmission electron microscopy shows extracellular regions to be the preferred localization of functionalized multiwalled carbon nanotubes in fresh plant root cells independent of their size and geometry. Penetration into the plant cell results in breaching of graphitic tubular structure of functionalized multiwalled carbon nanotubes with their length being shortened until ∼50 nm and diameters becoming thinner until less than 10 nm. The capability to agglomerate after translocation into the plant cells alarms potential cytotoxicity effect of functionalized multiwalled carbon nanotubes in agriculture. These work findings have suggested using urea functionalized multiwalled carbon nanotubes for effective nutrient delivery systems in rice plant.

Efficient use of urea fertilizer (UF) as important nitrogen (N) source in the world’s rice production has been a concern. Carbon-based materials developed to improve UF performance still represent a great challenge to be formulated for plant nutrition. Advanced N nanocarrier is developed based on functionalized multiwall carbon nanotubes (f-MWCNTs) grafted with UF to produce urea-multiwall carbon nanotubes (UF-MWCNTs) for enhancing the nitrogen uptake (NU) and use efficiency (NUE). The grafted N can be absorbed and utilized by rice efficiently to overcome the N loss from soil-plant systems. The individual and interaction effect between the specified factors of f-MWCNTs amount (0.10–0.60 wt%) and functionalization reflux time (12–24 hrs) with the corresponding responses (NUE, NU) were structured via the Response Surface Methodology (RSM) based on five-level CCD. The UF-MWCNTs with optimized 0.5 wt% f-MWCNTs treated at 21 hrs reflux time achieve tremendous NUE up to 96% and NU at 1180 mg/pot. Significant model terms (pvalue < 0.05) for NUE and NU responses were confirmed by the ANOVA. Homogeneous dispersion of UF-MWCNTs was observed via FESEM and TEM. The chemical changes were monitored by FT-IR and Raman spectroscopy. Hence, this UF-MWCNTs’ approach provides a promising strategy in enhancing plant nutrition for rice.