Nurlidia Mansor

A comprehensive review on biodegradable polymers and their blends used in controlled-release fertilizer processes

Abstract Biodegradable polymer-coated controlled-release fertilizers (PC-CRFs) are essential means to reduce cost, improve marketability, conserve land fertility, achieve high crop yields and combat climate challenges. It is known that about 15–30% of any fertilizer packed in a PC-CRF does not get released due to the concentration gradient difference across the polymer coatings. To release the trapped fertilizer(s), it is desired that polymer-based coatings should biodegrade after the fertilizer is completely released into the soil. This review has aimed to provide a comprehensive account for various biodegradable polymers/blends derived either from natural or synthetic sources which are cited in the literature for PC-CRFs. In addition, this review covers the discussion on their classification criteria, trends in the processes of fertilizer coatings, methodological issues for their biodegradation assessment, coating attributes that affect the biodegradability and an outlook into their biodegradation kinetic models that involve enzymes and microbial processes. It also concludes that experimental as well as modeling data are insufficient to assess the biodegradation contribution of the overall nutrient release in PC-CRFs.

Characterization of carbon nanofibers treated with thermal nitrogen as a catalyst support using point-of-zero charge analysis

The chemical and physical purification of carbon nanofiber exposes more anchoring sites between meal precursors and carbon surface but thermal N2 gas flow maintains the crystals structure as well as its defect and edge sites, referred to as active sites or anchoring sites. After calcination in nitrogen at 450°C, samples were characterized by Raman spectra X-ray diffraction, as well as thermogravimetric and nitrogen physisorption analyses. Results showed a relatively lower fraction of amorphous carbon to graphite, indicating a greater removal of amorphous carbon. Moreover, the disorder intensity of carbon nanofibers that were treated in N2 flow rate of 1 L/min and 3 hours, called 1Gcom-3h sample, achieved far more defect sites compared with unmodified carbon nanofiber. In addition, the surface areas of mesoporous carbon nanofibers decreased over prolonged residence time. The carbon nanofiber support-metal cation interaction therefore improved the deposition of iron when the point-of-zero charge reading was greater than four.

Lignin reinforcement of urea-crosslinked starch films for reduction of starch biodegradability to improve slow nitrogen release properties under natural aerobic soil condition

Abstract The urea-crosslinked starch (UcS) film has a major drawback of very rapid biodegradability when applied as slow release fertilizer in soil. Lignin reinforcement of the UcS was used to prepare composite films, aimed to reduce the starch biodegradability and slow the release of nitrogen in aerobic soil condition. Study results revealed that mineralization of the composite films was delayed from 6.40 to 13.58% more than UcS film. Inhibition of composite films mixing with soil, the Michaelis-Menten reaction rates for α-amylase were inhibited ~1.72–2.03 times whereas the Michaelis-Menten reaction rates for manganese peroxidase were increased ~1.07–1.41 times compared to UcS film. Saccharides–glucose, maltose and maltotriose demonstrated that their rates of formation (zero-order reaction) and depletion (first-order reaction); both were slowed more in aerobic soil which received the composite films. Increasing of lignin in composite films, the acid to aldehyde ratios of vanillyl and syringyl phenols of the lignin declined from 1.18 to 1.17 (~0.76%) and 1.59–1.56 (~1.78%), respectively. The diffusivity of nitrogen was effectively slowed 0.66–0.94 times by the lignin in composite films and showed a “Fickian diffusion” mechanism (release exponent n=0.095–0.143).

Lignin Loading Effect on Biodegradability and Nitrogen Release Properties of Urea Modified Tapioca Starch in Wet Soil

Plant based biopolymers are abundantly and easily available naturally biodegradable raw materials to prepare slow release nitrogen technologies. To test the lignin loading effect on biodegradability of the slow release fertilizer (SRF) and nitrogen release applications, a pot experiment under real soil conditions was conducted. Lignin at different loading percentages 5%, 10%, 15% and 20% were mixed with urea-modified tapioca starch acting as slow release fertilizer (SRF). Increasing the percentage of lignin to starch reduced the weight loss with improved nitrogen slow release properties in wet soil. Soil microbial biomass was negatively correlated with increase of lignin percentages. Lignin is a low cost biopolymer and can be used to improve starch biodegradation and its slow release nitrogen properties.

A review of mathematical modeling and simulation of controlled-release fertilizers

ABSTRACT Nutrients released into soils from uncoated fertilizer granules are lost continuously due to volatilization, leaching, denitrification, and surface run‐off. These issues have caused economic loss due to low nutrient absorption efficiency and environmental pollution due to hazardous emissions and water eutrophication. Controlled‐release fertilizers (CRFs) can change the release kinetics of the fertilizer nutrients through an abatement strategy to offset these issues by providing the fertilizer content in synchrony with the metabolic needs of the plants. Parametric analysis of release characteristics of CRFs is of paramount importance for the design and development of new CRFs. However, the experimental approaches are not only time consuming, but they are also cumbersome and expensive. Scientists have introduced mathematical modeling techniques to predict the release of nutrients from the CRFs to elucidate fundamental understanding of the dynamics of the release processes and to design new CRFs in a shorter time and with relatively lower cost. This paper reviews and critically analyzes the latest developments in the mathematical modeling and simulation techniques that have been reported for the characteristics and mechanisms of nutrient release from CRFs. The scope of this review includes the modeling and simulations techniques used for coated, controlled‐release fertilizers. Graphical Abstract Figure. No caption available.

Lignin Modified Urea Fertilizer's Biodegradation and Nitrogen Release under Reduced Soil Condition

Lignin is a natural biopolymer easily available in industrial waste and currently being used in slow release matrix improvements. Research work objective is to study the effect of 5% to 20% alkaline kraft lignin (AL) loadings on the biodegradation and nitrogen release in urea modified tapioca starch, acting as biodegradable slow release fertilizer (SRF) under reduced soil condition. Weight loss (%) of SRFs reduced from 76% to 35% with increasing %AL until day 28. Biodegradability (%) of SRFs affectively reduced at low 5-10%AL compared to high 15-20%AL. Nitrogen release was reduced with increasing the %AL in SRFs. Nitrogen release mechanism showed fickian diffusion mechanism (n<0.5) except for 10%AL (0.5<n<1). The lowest diffusion coefficient, 1.71 x 10-8cm2/s was observed in 10%AL. Fourier transformed infrared analysis of the biodegraded SRFs showed anhydroglucose ring asymmetric stretching vibration due to COC and COH (904-1140cm-1), lignins aromatic ring stretching (1451-1500cm-1) and deformation of C-H in lignins guaicyl ring or starch glucose ring (1162 cm-1). Lignin can effectively be used to improve nitrogen slow release and reduce biodegradability of SRFs under reduced soil.

The Study of Biodegradation Kinetics of Starch Based on Coating in Controlled Released Fertilizer (CRF)

The aim of this study is to prepare a starch film and analyze its characteristics in different pH condition. Starch has been given great attention and has been actively investigated to be used as coating materials for CRF because of its degradation properties. Once the analysis on the starch characteristics is completed, the reaction rate of the starch can be developed by using Michaelis-Menten equation as reference. The results of the reaction rate are important to help determine the biodegradation kinetics of the starch. It will also assist in determining the conditions needed to produce the starch film in order to reduce the release rate of fertilizer. Throughout this study, the biodegradation kinetics of starch film will be investigated and thus providing a reference for the selection of coating material for the application of CRF while improving agriculture production.

Investigation of Pb dispersal and accumulation around untreated former tin mines in Perak, Malaysia

There are approximately 114 000 ha of former mining area left derelict after the tin mining industry collapsed in Malaysia [1] These lands are currently turned into agriculture and aquaculture farms. Unfortunately, studies have indicated that crops cultivated on tin tailings have been found to contain alarming levels of Potentially Toxic Elements (PTEs). Fish that are bred in slurry ponds and mine pools are also not excluded from PTEs. This research aims to determine and identify the atmospheric dispersal as well as the accumulation of Pb from active and derelict former tin mines in Perak, Malaysia. Samples of plants; Melastoma sp. and Benincasa sp. and fish; Tilapia sp. and Cichla sp. grown and bred in mining ponds were collected from active farms in Location 1 and 2. Plants and fish of the same species and grown naturally were also taken from abandoned mine sites at Location 3 and 4. Atmospheric dispersal of heavy metals is also investigated using available biomarkers. Tree bark from Acacia mangium sp. is collected to represent heavy metal dispersal from wind erosion of tin tailings from the mine sites. The methodology for sample analysis was done by using wet digestion analysis with nitric acid and hydrochloric acid. Concentration of heavy metals was determined using flame atomic absorption spectrometry (FAAS). Pb concentration was found to be highest in the root of Melastoma sp. at 57.62 mg/kg and in the muscle of Cichla sp. at 27.28 mg/kg. The results indicate elevated Pb levels regardless of whether it is from active or abandoned tin mine site. Heavy metal levels in all of the plants and fish samples in this study were found to be above the safe limit issued in the Food Acts 1983 and Regulations 1985[2][14]. Appropriate measures should be taken to further reduce the dispersal and exposure of heavy metals from the former mine sites from entering into the food chain and causing serious threat towards health and safety.

Reaction-Multi Diffusion Model for Nutrient Release and Autocatalytic Degradation of PLA-Coated Controlled-Release Fertilizer

A mathematical model for the reaction-diffusion equation is developed to describe the nutrient release profiles and degradation of poly(lactic acid) (PLA)-coated controlled-release fertilizer. A multi-diffusion model that consists of coupled partial differential equations is used to study the diffusion and chemical reaction (autocatalytic degradation) simultaneously. The model is solved using an analytical-numerical method. Firstly, the model equation is transformed using the Laplace transformation as the Laplace transform cannot be inverted analytically. Numerical inversion of the Laplace transform is used by employing the Zakian method. The solution is useful in predicting the nutrient release profiles at various diffusivity, concentration of extraction medium, and reaction rates. It also helps in explaining the transformation of autocatalytic concentration in the coating material for various reaction rates, times of reaction, and reaction-multi diffusion. The solution is also applicable to the other biodegradable polymer-coated controlled-release fertilizers.

Identifying Thermal and pH Stability of Thiols Compound in Garlic Extract

Thiosulfinates are a major compound found in most allium plant. Garlic, an allium species shows its potential to inhibit microbial and enzyme activity. The usage of garlic is widely known especially in the agriculture field. Thiosulfinates are formed by reaction of alliinase enzyme from their respective S-alk(en)yl cysteine sulfoxide after the crushing process of the garlic cloves. The stability of the garlic extract has been tested at variations of temperatures and pH values at different incubation time in terms of concentration (mM). After consecutive 4 hour incubation, thiols show higher concentration at temperature 30-35°C. The minimum concentration shows 22% reduction from the original thiols reading. Meanwhile, pH values of 2 (acidic) at 35°C gives higher thiols concentration compared to other conditions.