Hydroxyapatite Nano-Fertilizers Effects on Adsorption and Uptake of Cadmium and Lead, Nutrient Release and Growth Performance of Selected Crops
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Date
2023-09
Authors
Nyaenya, Ngorwe Evans
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
ABSTRACT
More than 9.1 million people globally are affected by famine. Spinach, kales and beans are among vegetables promoted for consumption as an intervention strategy. Until the development of nanofertilizers such as synthetic hydroxyapatite (Syn nHA), boosting vegetable production has been by employing commercial and organic fertilizers. Other than being micro-sized, nanofertilizers have reduced uptake of harmful heavy metals like Pb, Cd, and improved growth performance (height, dry weight, leaf diameter and number of leaves) of crops due to their numerous adsorption sites. Further advantages include, being stable, non-toxic and having enhanced surface area to volume ratio. Use of over 130 billion tones of bone being dumped per year to prepare nanofertilizers is likely to reduce its environmental menace. This study envisaged using bones to synthesize nanofertilizers (bone nHA) and. investigated the effect of bone nHA and Syn nHA nano-fertilizers on Cd and Pb uptake and adsorption, growth performance, and nutrient release in beans, spinach and kale leaves grown for a 90 day period. Both bone-nHA and Syn nHA were encapsulated with commercial DAP and NPK fertilizers. The techniques SEM, XRD, and FTIR were employed to characterize the nanofertilizers, while AAS was used to determine levels of Cd and Pb, and UV measured NO3- and PO43-levels. The bone nHA was less coagulated with significantly smaller diameter compared to Syn nHA (P˂0.05). Further, bone-nHA significantly reduced Cd (range 58 – 89 %) and Pb (range 62 - 91 %) uptake and had higher adsorption of the metals (P˂0.05). Growth performance parameters for the crops grown with bone-nHA improved by over 56 %, being better than those grown with the Syn nHA and it is encapsulated nanofertilizers (P˂0.01). Results support presence of higher number of adsorption sites in the bone-nHA implying a better performance as a nanofertilizer. At 40 days bone nHA had significantly higher nitrate release rate of 28 % in comparison with syn nHA (P˂0.01). Adsorption equilibrium data fitted well with Langmuir for Cd while Pb fitted well with Freundlich isotherm. Bone nHA nanofertilizers are recommended to reducing Cd and Pb uptake and adsorption, improving growth performance and nutrient release on growing beans (P. Vulgaris L.), spinach (Spinacia oleracea) and kales (Brassica oleracea acephala).
Description
A Thesis Submitted in Fulfillment of the Requirements for the Award of the Degree of Doctor of Philosophy (Chemistry) in the School of Pure and Applied Sciences of Kenyatta University,September, 2023.
Keywords
Hydroxyapatite Nano-Fertilizers Effects on Adsorption and Uptake of Cadmium and Lead, Hydroxyapatite Nano-Fertilizers, Hydroxyapatite Nano-Fertilizers Effects, Adsorption and Uptake of Cadmium, Adsorption and Uptake of Lead, Lead, Cadmium