Bio-based Large Tablet Controlled-Release Urea: Synthesis

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Agricultural and Environmental Chemistry

Bio-based Large Tablet Controlled-Release Urea: Synthesis, Characterization, and Controlled-Released Mechanisms Lu Liu, Tianlin Shen, Yuechao Yang, Bin Gao, Yuncong C. Li, Jiazhuo Xie, Yafu Tang, Shugang Zhang, Zhonghua Wang, and Jianqiu Chen J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.8b04042 • Publication Date (Web): 20 Sep 2018 Downloaded from http://pubs.acs.org on October 4, 2018

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Journal of Agricultural and Food Chemistry

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Title

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Bio-based Large Tablet Controlled-Release Urea: Synthesis, Characterization, and

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Controlled-Released Mechanisms

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Authors:

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Lu Liua,+, Tianlin Shena,+, Yuechao Yanga,c,*, Bin Gaob, Yuncong C. Lic, Jiazhuo Xiea, Yafu

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Tanga, Shugang Zhanga, Zhonghua Wanga, Jianqiu Chend

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Affiliations:

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a

National Engineering Laboratory for Efficient Utilization of Soil and Fertilizer Resources;

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National Engineering & Technology Research Center for Slow and Controlled Release

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Fertilizers, College of Resources and Environment, Shandong Agricultural University, Taian,

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Shandong 271018, China

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b

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University of Florida, Gainesville, FL 32611, USA

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c

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University of Florida, Homestead, FL 33031, USA

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d

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Engineering Group Co., Ltd, Linshu, Shandong 276700, China

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+

Agricultural and Biological Engineering, Institute of Food and Agricultural Sciences (IFAS),

Department of Soil and Water Science, Tropical Research and Education Center, IFAS,

State Key Laboratory of Nutrition Resources Integrated Utilization, Kingenta Ecological

Lu Liu and Tianlin Shen contributed equally to this work.

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*

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Yuechao Yang

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Phone: 86-538-8242215

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E-mail: [email protected].

Corresponding author

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1 ACS Paragon Plus Environment


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ABSTRACT

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To improve nitrogen (N) use efficiency and minimize environmental pollution caused by

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fertilizer over use, novel bio-based large tablet controlled-release urea (LTCRU) was prepared

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by using bio-based coating materials to coat large tablet urea (LTU) derived from urea prills

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(U). Nano fumed silica (NFS) was added to the bio-based coating materials to improve the

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slow-release properties. Surface area of the LTU and U was measured by three-dimension

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scanning. Compared with U, LTU had smaller surface area-to-weight ratio, which can reduce

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the coating materials. Scanning electron microscope analysis showed that the addition of NFS

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in bio-based coating materials reduced the porosity of the coating shells of LTCRUs and thus

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enhanced the N release longevity of the controlled-released fertilizer. Depending on the pores

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on the coating shells of LTCRU, two N release patterns were revealed. Because of the good

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release characteristics, the novel LTCRU shows great potential to support sustainable

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agricultural production.

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KEYWORDS: Modified large tablet controlled-release urea; Surface area; Bio-based

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material; Nano fumed silica; Release rate


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INTRODUCTION

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With rapid growth of global populations, agricultural production is requiring more and

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more fertilizers to meet the demand for food.1 Nitrogen (N) fertilizers, especially urea, should

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be applied in a controlled-release manner to increase their efficiency as well as to prevent

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their loss via ammonia volatilization and leaching for soil and water pollution.2

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Controlled-release urea (CRU) fertilizer can enhance crop yield and nutrient use efficiency

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(NUE) with lower environment impact in comparison with the traditional N fertilizers.3-6

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However, the high cost of coating materials of CRU and complicated production procedure

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have limited their larger scale application in agricultural fields. In addition, most of the

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coating materials are derived from petroleum resources which are expensive and

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non-renewable. The coating shells may present potential risks to pollute the soil environment

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after the nutrients are released from CRUs.7-8

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Another method to improve the NUE is the use of urea super granules (USG), invented by

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the International Fertilizer Development Center.9 Several studies have shown that the use of

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USGs can not only reduce the ammonia volatilization losses but also reduce the usage of

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fertilizer in the fields compared to the traditional fertilizer.10-11 However, USG without

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coating must be placed deeply to avoid the burn of seeds or plant roots and ammonia

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volatilization by fast dissolving in paddy soil. The deep placement method of the USG is

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labor intensive and time consuming which has limited it used in large-scale agricultural

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production systems.12 To solve these problems, novel large tablet polymer-coated urea

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(LTPCU) has been produced by using the bio-based coating materials to coat on the surface

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of LTU. Compared to normal CRU (diameter of 2-4 mm), LTPCU is more effective to save

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the production cost by decreasing the usage of coating material.13 Therefore, LTPCU is more

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suitable to be used in the agricultural production system.

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Many types of materials have been used as coatings for CRU,14 including sulfur,15



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petroleum based polymers such as polyurethane (PU),16 and bio-based polymers derived from

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starch,17 cellulose,18-19 and vegetable oil.20 Castor oil could be used as the bio-polyol to

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produce polyurethane without further treatments because of its high hydroxyl value. The use

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of bio-based polymers as the coating for CRU has attracted much research attention recently

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because they are more environmentally friendly than petrochemicals.21 However, most of the

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bio-based coating materials are hydrophilic and the nutrient controlled release longevity is

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hard to over 30 days of the bio-based CRUs.22 With the development of polymer technology,

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it is possible to use some new modification technologies (nano materials, hydrophobic organ

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silicon compounds) for the bio-based coating to improve the nutrient release characteristics of

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bio-based CRU.23-25 In addition, research efforts have been made in understanding CRU’s

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controlled-release process and behavior. The governing release characteristics and

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mechanisms of CRU have been proposed and tested in previous studies. Findings from those

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studies have suggested that the release of CRU is governed by simultaneous transport of both

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liquid and vapor water between the inside and outside of the coating.26-27 The cracks and

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micro pores existing on coatings are the main tunnels for the release.14 Controlled-release

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systems have been developed and often used as mimics to study and evaluate the

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controlled-release characteristics of CRUs. However, how much the modified bio-based

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coating shells can influence the nutrient release characteristics, and what are the nutrient

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release mechanisms of the modified large tablet controlled-release urea (MLTCRU) have not

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been established and evaluated in previous studies.

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The objective of this study was to prepare and evaluate the MLTCRU. Large tablet urea

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(LTU) was first produced from urea powder with a tablet machine. Bio-based coating

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materials derived from castor oil modified with nano fumed silica were then coated on the

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LTU surface at different loadings to obtain the MLTCRUs. The differences between the

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coatings of LTCRU and MLTCRU were characterized by SEM and FTIR. The nutrient


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release characteristics of LTCRU and MLTCRU were evaluated with a laboratory

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controlled-release system to quantify the release pattern as a function of volume change and N

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release rate. The ultimate goal of this study is to develop a high efficiency and

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environmentally friendly fertilizer.

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EXPERIMENTAL SECTION

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Materials. Urea prills (particle size of 0.5-2 mm with 46.2% N) were purchased from Luxi

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Chemical Co., Ltd (Shandong, China). Methylene diphenyl diisocyanate (MDI) with 30.03

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wt. % NCO group were obtained from Yantai Wanhua Polyurethane Co., Ltd. (Shandong,

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China). Bio-polyol produced from castor oil and NFS was purchased from Aladdin Industrial

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Co., Ltd. (Shanghai, China). Previous studies demonstrated that bio-polyol derived from

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castor oil is biodegradable.28-31 With high hydroxyl value of 137.81±0.58 mg KOH/g, castor

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oil is an ideal bio-based coating material. All the chemical agents were analytical grade and

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used directly as received. Deionized water was used throughout the experiment.

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Preparation of LTU. The LTUs were prepared from conventional urea prills. The urea

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prills were mechanically molded into LTU using an extruder (YST-100T, Changzhou Jiuyajiu

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Machinery Manufacturing Co. Ltd., China) under the pressure of 10 T (Ton). The height and

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diameter of each tablet was 11.20 mm and 16.00 mm. The mass of each LTU was around

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1.85-2.15 g and the N content of each LTU was about 0.85-0.99 g. The volume and surface

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area of LTU were determined using the three-dimensional scanning technology with a laser

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scanner (SLP-250, Wuxi SGKs Measurement Technology Co., Ltd., China), and the surface

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area-to-weight ratio was calculated by surface area/ weight.32-33 A three-dimensional laser

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scanner was used for this study. The surface area-to-weight ratio was used to express the

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result in Table 1.

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Preparation of LTCRU. To make bio-based coated fertilizers, 3 kg of LTUs were put in a

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rotating drum in a coating machine (Taizhou Liming pharmaceutical machinery Co., LTD,



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China) and preheated by blasting hot air of 70±2 °C. Then 30g of the mixture of coating

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materials (15 g of bio-polyol and 15 g of MDI) were sprayed onto the surfaces of LTUs. The

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heat-curing reaction of the mixed coating materials was finished in the rotating drum in 15

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min and the coating materials were coated on the surfaces of the fertilizers by forming a layer

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of coating. This process was repeated for six times to make LTCRU1, eight times to make

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LTCRU2. The actual percentage of coating material in each coated fertilizer was determined

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by measuring coating materials used as following. The 50 g of a coated fertilizer was crushed

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and placed into 80 ml deionized water to dissolve urea out of the coating. The remaining

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material was dried at 60±5 °C for 4 h. The weight of coating materials used was recoded. The

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percentage of both coating material and N contents in the LTCRUs are listed in Table 2. The

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actual coating content ranged from 1.83-3.04%. The use efficiency of coating materials is not

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high with a rotating drum used in this study and could be much high with a fluidized bed

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coating equipment commonly used for the scale-up production.

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To make the modified bio-based coated fertilizers, 2.5 g of the NFS particles (0.5 wt. % of

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the coating) were first dispersed in both 500.0 g of bio-polyol and 500.0 g of MDI through

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fast stirring and ultra-sonication for an hour.34-38 Then, 15.0 g of each dispersion was mixed

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and dropped onto the surfaces of the fertilizer particles in the rotation drum. The same coating

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procedures were applied to prepare the modified fertilizers, which were labeled

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correspondingly as MLTCRU1 and MLTCRU2.

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Characterization of LTCRU and MLTCRU Coatings. The coatings of LTCRU and

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MLTCRU were dried at 65 °C for 24 h. They were then analyzed by a Fourier Transform

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Infrared (FTIR) spectroscopy (Nicolet IS10) at the wavenumber range of 4000 to 500 cm-1.

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With the help of the scanning electron microscopy coupled with energy dispersive X-ray

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Spectroscopy (SEM-EDS, FEI Quanta 650 and SU8010), the morphologies and element

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compositions of the coatings were determined under high-vacuum conditions. Metal spraying


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was used to increase the electro-conductivity of these samples for better SEM images. The

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water contact angle (WCA) of the coating materials of LTCRU and MLTCRU were measured

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with an optical contact angle meter (Powereach, JC2000C2).

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Nitrogen Release Characteristics of LTCRU and MLTCRU. The percentages of N

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content released from LTCRU and MLTCRU in the first 24 h were measured in still deionized

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water at 25 °C. Five tablets (10.00±0.75g, three replicates) were placed in a glass bottle

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containing 200 mL of deionized water and kept in an incubator at 25±0.5 °C. The amount of

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N released from the coated fertilizers at 1, 3, 5, 7, 10, 14, 28, 56, 84, 112 and 140 days were

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measured with the Kjeldahl method.19 When the cumulative N release reached or was over 80 %

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of the total N, the coated fertilizers were taken out from the bottles. The release characteristics

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of single LTCRU or MLTCRU in deionized water were also determined in a 50 mL centrifuge

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tube at 25 °C. Incubation conditions and experimental method were the same. The amount of

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N released from the coated fertilizers at 1, 3, 5, 7, 10, 14, 28, 56, 84 days were measured with

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the Kjeldahl method.

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RESULTS AND DISCUSSION

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Comparison of Urea Prill and LTU. Three-dimensional scanning technology was used to

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measure the volumes and surface areas of the fertilizers in graphic models (Figure 1a1, b1).

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After being mechanically molded, urea prills (Figure 1a1, 2.00-4.00 mm average diameter and

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0.03±0.01 g average weight) became LTU (Figure 1b1, 16.00 mm of diameter and 2.00±0.15 g

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average weight). After the mechanical extruding, the shape of LTU was more regular than that

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of urea prill. The surface area of the fertilizers was measured (Table 1). The surface

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area-to-weight ratio of LTU was 359.36 mm2·g-1 which is much less than that of urea prill

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(1257.78 mm2·g-1). The SEM analysis with two magnifications was performed to compare the

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surface morphology of the urea prill and LTU. For the images of 30× magnifications, the

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surfaces of urea prill and LTU showed no clear differences (Figure 1a2, b2). At 200×



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magnification, the surface of urea prill showed small bumps (Figure 1a3). As a result, LTU is a

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better core than the urea prill for the production of coated fertilizer because of its smoother

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surface and lower surface area-to-weight ratio.39-40 The coating of LTU may also use less

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materials and thus has lower production cost than that of urea prill.13

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Photographs of Coating Materials and Fertilizers. Bio-polyol, bio-polyol mixed with

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NFS particles, MDI and MDI mixed with NFS particles were respectively put into four glass

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bottles and then stewed for two months in an incubator at 25±0.5 °C to verify the stability of

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NFS in coating materials. NFS remained uniformly dispersed in the bio-based polyols,

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demonstrating great stability without coagulation or other types of inter-facial instability

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(Figure 2Ab). However, NFS caused solidification in MDI (Figure 2Ad) due to the reaction

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between Si-O of NFS and NCO groups of MDI. These results suggest that fumed silica should

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be dispersed in bio-based polyols to avoid potential aggregations when used to prepare

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coating materials for controlled-release fertilizers. The coating materials in Figure 2A were

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uniformly coated onto the surfaces of LTU in the rotating drum to make the LTCRU1 and

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MLTCRU1 (Figure 2C). The entire LTUs including edges were coated with the bio-based

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material. With the addition of NFS, the coating of MLTCRU showed a smoother surface than

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that of LTCRU, which can improve mechanical properties.41-44

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FTIR Spectra of LTCRU and MLTCRU Coatings. The coating structures of MLTCRU,

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LTCRU, MDI and bio-based polyol were examined by FTIR (Figure 3). The NH-CO at 1601

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cm-1 in Figure 3c and Figure 3d suggests the existence of polyurethane after the reaction

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between bio-based polyol (Figure 3a) and MDI (Figure 3b).45 The Si-O stretching of the

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fumed silica located at 1100 cm-1 overlapped with the 1080 cm-1 absorption band of the

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C-O-C stretching. Compared with LTCRU, MLCRU showed a larger peak at this wavelength

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from the absorption of NFS. It is also noteworthy that the spectra of MLTCRU and LTCRU

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show high intensity of NCO at 2280 cm-1, suggesting that the coating might contain unreacted


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isocyanate. In addition, the lowered relative ratios of peaks at 2280 cm-1 of MLTCRU can be

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attributed to the reaction between NFS and MDI via cross-linking of OH groups as the same

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phenomenon in Figure 2A.36, 38

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Morphology of Coatings. The morphologies of the fertilizer coating surfaces and their

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water contact angles are demonstrated in Figure 4. The surface morphology of LTCRU1

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(Figure 4a1) presented a wrinkled and porous appearance with a water contact angle of

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30.57±1.08°. After being modified by the NFS, the water contact angle increased by about 5°

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to 35.11±0.46°. No clearly changes of hydrophobic property of coating surfaces were found

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after the modification because NFS was dispersed uniformly in the coatings including surface

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and cross section. The cross-section morphologies of the LTCRU1 and MLTCRU1 coatings

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are demonstrated in Figure 4a3 and 4b3, respectively. Pores with diameters even larger than 20

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µm were found in the coating of LTCRU1 (Figure 4a3). However, large pores were not

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detected in the coating of MLTCRU1 (Figure 4b3) indicating that the addition of NFS can

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reduce the porosity of the coatings. The images showed presence and distribution of the NFS

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in MLTCRU1 coatings (Figure 4b2 and 4b4) but not in LTCRU1 coating (Figure 4a2 and 4a4).

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NFS particles were found in the surface and cross section of MLTCRU1 coatings (Figure 4b2

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and 4b4). The differences between LTCRU1, MLTCRU1 and LTCRU2, MLTCRU2 are only

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coating contents. Therefore, the morphology of LTCRU2 and MLTCRU2 were put in Figure

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S1 in Supporting Information.

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Nitrogen Release Characteristics of LTCRU and MLTCRU. The most important

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characteristic of coated fertilizers is their slow-release property.18 The N release characteristic

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curves of LTCRU1, LTCRU2, MLTCRU1 and MLTCRU2 are presented in Figure 5 and four

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mathematical models were derived based N release data. The N release rates can be calculated

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based on the following four equations:

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For LTCRU1: y = 11.98ln(x) + 39.44, R2 = 0.8340;



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For LTCRU2: y = 0.67x + 1.99, R2 = 0.9967;

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For MLTCRU1: y = 10.51ln(x) + 31.88, R2 = 0.8487;

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For MLTCRU2: y = 0.60x - 1.82, R2 = 0.9727.

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Where Y is the nitrogen accumulative release (%) and X is the incubation time (days). The

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N initial release rates during the first seven days for LTCRU1 and MLTCRU1 (both had 2 wt. %

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coating) were almost identical without notable differences. When the incubation time reached

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28 days, LTCRU1 had reached a cumulative N release rate of 89.38±4.13 %, but the

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corresponding release rate of MLTCRU1 was only 74.40±3.75 %. The International standard

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for CRFs (ISO 18644-2016) is that cumulative release mass fraction of nutrient in 28 days

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should be less than 75%.46 Therefore, MLTCRU1 reduced the release rate by 15 % compared

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to LTCRU1 and met the standard.

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When the coating increased to 3 wt. % and the incubation time reached seventh day, the

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cumulative N release rates of LTCRU2 and MLTCRU2 were 7.14±3.12 % and 5.44±3.15 %,

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respectively which were not significantly different. After 28 days, the cumulative N release

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rate of LTCRU2 reached 23.87±1.32 %, almost twice of the corresponding release rate of

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MLTCRU2 (12.02±1.99 %). Even though both LTCRU2 and MLTCRU2 met the ISO

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standard, MLTCRU2 showed the superior release behavior to fit crops which are slow growth

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and low nutrient demand during first 28 days.

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N release characteristics of the coated fertilizers are significantly affected by the contents

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of the coating materials. In this study, when the coating contents increased from 2 wt. % to 3

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wt. %, the N release longevity of the coated fertilizers increased significantly. When the

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coating content was 2 wt. %, N release of LTCRU1 and MLTCRU1 were 92.98±1.24 % and

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90.05±1.86 % after 84 days incubation. When the coating content was added to 3 wt. %, N

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release of LTCRU2 and MLTCRU2 were 58.42±2.10 % and 40.25±1.68 % after 84 days

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incubation. The N release longevity of LTCRU2 and MLTCRU2 were prolonged to about 140


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days when the N accumulative release was 93.84±1.15 % and 90.24±1.83 %, respectively. As

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the coating materials increase on the fertilizer layer by layer, the liquid pathways of water and

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dissolved urea had to diffuse through more layers to get in and out which solw the release of

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fertilizers. Therefore, with more coating contents, LTCRU2 and MLTCRU2 have a bettter

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controlled-release capacity than LTCRU1 and MLTCRU1, respectively. In addition, the

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results indicate that NFS modification can significantly improve the N release longevity of

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coated fertilizers. Previous studies have shown that NFS can modify PU resulting in improved

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rheological properties, hydrophobic surface, mechanical properties, and thermal stability with

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small amount of addition.34 As a result, the controlled-release property of modified coating is

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enhanced.47

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Releasing Patterns of CRU. The N release from the CRUs may have two different release

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patterns. For the first patter (LTCRU), the release can be divided into four stages (Figure 6).

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After being dropped into deionized water, LTCRU fertilizers with pores on their coatings

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started absorbing water to show the first release stage, the wetting stage. Water absorption and

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wetting of the coating material led to the initial releasing stage (Figure 6a). During this stage,

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water passed through the pores on the coating and dissolved the urea out of the coating from

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one side which bigger holes existed, thereby causing the release of N with more urea loss, the

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urea core of LTCRU became irregular and incomplete and there existed an obvious

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permeation pressure difference between the inside and outside of the coating, leading to the

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fast dissolution (Figure 6b) and slow dissolution (Figure 6c) stages. The shape and position of

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the urea core remaining in the coating depended on the locations of the release pores. Finally,

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the entire urea core in the coating was dissolved; the nutrient concentration within the coating

263

began to decrease during the release, slowing down overall fertilizer release rate. The final

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permeation stage (Figure 6d) showed a slower steady release characteristic in comparison to

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other stages because N concentration inside the coating and the permeation pressure



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decreased.

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MLTCRU fertilizers followed the release pattern 2 (Figure 7). During the wetting stage in

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the first three days, there was no change in N release and fertilizer volume (Figure 7a). In the

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dissolution stage, water or vapor went through the coating and slowing N release without

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notable fertilizer volume changes (Figure 7b). At the end of this stage, a thin layer of water

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between the urea core and coating was visually observed. With more and more urea dissolved

272

in the water inside the coating, the permeation pressure between the inside and outside of the

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coating increased. As a result, the coating was stretched to decrease the permeation pressure,

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leading to the increase in fertilizer volume during the swelling stage (Figure 7c). In this stage,

275

there existed both urea core and solution inside the coated fertilizer tablet. As the MLTCRU

276

fertilizer approached its maximum volume, the release rate speeded up. Urea core and

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solution left inside the coating spread out steadily during the final stage (Figure 7d).

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A combination of these two release patterns led to a relatively steady characteristic of N

279

release from the LTCRU. Findings from this study indicate that NFS modification can extend

280

the N release longevity of the coated fertilizer. The bio-based LTCRUs demonstrate good

281

controlled-release characteristics and thus can be a promising controlled-release fertilizer for

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field applications.


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ASSOCIATED CONTENT

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Supporting Information

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Morphology of coatings (LTCRU2 and MLTCRU2)

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AUTHOR INFORMATION

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Corresponding Author

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Tell: +86-538-824-2900 (China)

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Fax: +86-538-824-2250 (China)

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Email: [email protected]

292

Acknowledgements

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This research was funded by the National Natural Science Foundation of China (Grant

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31572201), National Key R&D Program of China (2017YFD0200702), Shandong Province

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Key R&D Program (2017CXGC0306), Taishan industrial experts programme

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(LJNY201609), Shandong Agricultural Innovation Team (Grant SDAIT-17-04), the Project

297

of Shandong Province Education Department (Grant ZR2014JL023 and J16LF01) and

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Shandong Youth Education Science Program for College Students (Grant 17BSH113).

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Notes

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The authors declare no competing financial interest.



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REFERENCES

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(1) Azeem, B.; KuShaari, K.; Man, Z. B.; Basit, A.; Thanh, T. H. Review on materials &

304

methods to produce controlled release coated urea fertilizer. J. Controlled Release 2014, 181,

305

11-21.

306

(2) Shaviv, A. In Controlled release fertilizers, IFA international workshop on

307

enhanced-efficiency fertilizers, Frankfurt. International Fertilizer Industry Association Paris,

308

France: 2005; pp 28-30.

309

(3) Geng, J.; Ma, Q.; Chen, J.; Zhang, M.; Li, C.; Yang, Y.; Yang, X.; Zhang, W.; Liu, Z.

310

Effects of polymer coated urea and sulfur fertilization on yield, nitrogen use efficiency and

311

leaf senescence of cotton. Field Crops Res. 2016, 187, 87-95.

312

(4) Geng, J.; Ma, Q.; Zhang, M.; Li, C.; Liu, Z.; Lyu, X.; Zheng, W. Synchronized

313

relationships between nitrogen release of controlled release nitrogen fertilizers and nitrogen

314

requirements of cotton. Field Crops Res. 2015, 184, 9-16.

315

(5) Yang, X.; Geng, J.; Li, C.; Zhang, M.; Chen, B.; Tian, X.; Zheng, W.; Liu, Z.; Wang, C.

316

Combined application of polymer coated potassium chloride and urea improved fertilizer use

317

efficiencies, yield and leaf photosynthesis of cotton on saline soil. Field Crops Res. 2016, 197,

318

63-73.

319

(6) Zheng, W.; Sui, C.; Liu, Z.; Geng, J.; Tian, X.; Yang, X.; Li, C.; Zhang, M. Long-term

320

effects of controlled-release urea on crop yields and soil fertility under wheat–corn double

321

cropping systems. Agron. J. 2016, 108 (4), 1703-1716.

322 323 324 325

(7) Doran, J. W. Soil health and global sustainability: translating science into practice. Agric., Ecosyst. Environ. 2002, 88 (2), 119-127. (8) Lyu, X.; Yang, Y.; Li, Y.; Fan, X.; Wan, Y.; Geng, Y.; Zhang, M. Polymer-coated tablet urea improved rice yield and nitrogen use efficiency. Agron. J. 2015, 107 (5), 1837-1844.


Page 14 of 30

Page 15 of 30


326

(9) Katyal, J.; Vlek, P. Effect of granule size and the placement geometry on the efficiency of

327

urea supergranules for wetland rice grown on a permeable soil. Fertilizer research 1988, 15

328

(2), 193-201.

329

(10)

Bandaogo, A.; Bidjokazo, F.; Youl, S.; Safo, E.; Abaidoo, R.; Andrews, O. Effect of

330

fertilizer deep placement with urea supergranule on nitrogen use efficiency of irrigated rice in

331

Sourou Valley (Burkina Faso). Nutrient cycling in agroecosystems 2015, 102 (1), 79-89.

332 333 334 335 336

(11)

Sudhakara, K.; Prasad, R. Ammonia volatilization losses from prilled urea, urea

supergranules (USG) and coated USG in rice fields. Plant Soil 1986, 94 (2), 293-295. (12)

Sikder, R.; Xiaoying, J. Urea super granule (USG) as key conductor in agricultural

productivity development in Bangladesh. Developing Country Studies 2014, 4, 132-9. (13)

Yang, Y.-c.; Zhang, M.; Li, Y.; Fan, X.-h.; Geng, Y.-q. Improving the quality of

337

polymer-coated urea with recycled plastic, proper additives, and large tablets. J. Agric. Food

338

Chem. 2012, 60 (45), 11229-11237.

339 340 341 342

(14)

Naz, M. Y.; Sulaiman, S. A. Slow release coating remedy for nitrogen loss from

conventional urea: a review. J. Controlled Release 2016, 225, 109-120. (15)

Martin, E. Trenkel. Improving Fertilizer Use Efficiency Controlled-Release and

Stabilized Fertilizer In Agriculture. International Fertilizer Industry Association 1997.

343

(16)

Randall, D.; Lee, S. The polyurethanes book. Wiley: 2002.

344

(17)

Qiao, D.; Liu, H.; Yu, L.; Bao, X.; Simon, G. P.; Petinakis, E.; Chen, L. Preparation

345

and characterization of slow-release fertilizer encapsulated by starch-based superabsorbent

346

polymer. Carbohydr. Polym. 2016, 147, 146-154.

347

(18)

Xie, L.; Liu, M.; Ni, B.; Wang, Y. Utilization of wheat straw for the preparation of

348

coated controlled-release fertilizer with the function of water retention. J. Agric. Food Chem.

349

2012, 60 (28), 6921-6928.

350

(19)

Zhang, S.; Yang, Y.; Gao, B.; Wan, Y.; Li, Y. C.; Zhao, C. Bio-based interpenetrating



351

network polymer composites from locust sawdust as coating material for environmentally

352

friendly controlled-release urea fertilizers. J. Agric. Food Chem. 2016, 64 (28), 5692-5700.

353

(20)

Liu, X.; Yang, Y.; Gao, B.; Li, Y. Organic silicone‐modified transgenic soybean oil

354

as bio‐based coating material for controlled‐release urea fertilizers. J. Appl. Polym. Sci.

355

2016, 133 (41).

356

(21)

Xie, J.; Yang, Y.; Gao, B.; Wan, Y.; Li, Y. C.; Xu, J.; Zhao, Q. Biomimetic

357

Superhydrophobic Biobased Polyurethane-Coated Fertilizer with Atmosphere “Outerwear”.

358

ACS applied materials & interfaces 2017, 9 (18), 15868-15879.

359

(22)

Yang, Y.; Tong, Z.; Geng, Y.; Li, Y.; Zhang, M. Biobased polymer composites derived

360

from corn stover and feather meals as double-coating materials for controlled-release and

361

water-retention urea fertilizers. J. Agric. Food Chem. 2013, 61 (34), 8166-8174.

362

(23)

Picca, R. A.; Paladini, F.; Sportelli, M. C.; Pollini, M.; Giannossa, L. C.; Di Franco,

363

C.; Panico, A.; Mangone, A.; Valentini, A.; Cioffi, N. Combined approach for the

364

development of efficient and safe nanoantimicrobials: The case of nanosilver-modified

365

polyurethane foams. ACS Biomaterials Science & Engineering 2016, 3 (7), 1417-1425.

366

(24)

Lü, X.; Cui, Z.; Wei, W.; Xie, J.; Jiang, L.; Huang, J.; Liu, J. Constructing

367

polyurethane sponge modified with silica/graphene oxide nanohybrids as a ternary sorbent.

368

Chem. Eng. J. 2016, 284, 478-486.

369

(25)

Zhang, S.; Yang, Y.; Gao, B.; Li, Y. C.; Liu, Z. Superhydrophobic controlled-release

370

fertilizers coated with bio-based polymers with organosilicon and nano-silica modifications.

371

Journal of Materials Chemistry A 2017, 5 (37), 19943-19953.

372 373 374 375

(26)

Shavit, U.; Reiss, M.; Shaviv, A. Wetting mechanisms of gel-based controlled-release

fertilizers. J. Controlled Release 2003, 88 (1), 71-83. (27)

Shavit, U.; Shaviv, A.; Shalit, G.; Zaslavsky, D. Release characteristics of a new

controlled release fertilizer. J. Controlled Release 1997, 43 (2-3), 131-138.


Page 16 of 30

Page 17 of 30

376 377 378


(28)

Mutlu, H.; Meier, M. A. Castor oil as a renewable resource for the chemical industry.

Eur. J. Lipid Sci. Technol. 2010, 112 (1), 10-30. (29)

Jeon, H.; Kim, M.-N.; Park, E.-S. Thermal, mechanical and biodegradation properties

379

of pure, epoxidized and methoxylated castor oil based polyurethane. Plastics, Rubber and

380

Composites 2016, 45 (1), 1-8.

381

(30)

Oprea, S.; Potolinca, V. O.; Gradinariu, P.; Joga, A.; Oprea, V. Synthesis, properties,

382

and fungal degradation of castor-oil-based polyurethane composites with different cellulose

383

contents. Cellu 2016, 23 (4), 2515-2526.

384

(31)

Das, S.; Pandey, P.; Mohanty, S.; Nayak, S. K. Evaluation of biodegradability of

385

green polyurethane/nanosilica composite synthesized from transesterified castor oil and palm

386

oil based isocyanate. Int. Biodeterior. Biodegrad. 2017, 117, 278-288.

387

(32)

Igathinathane, C.; Davis, J. D.; Purswell, J. L.; Columbus, E. P. Application of 3D

388

scanned imaging methodology for volume, surface area, and envelope density evaluation of

389

densified biomass. Bioresour. Technol. 2010, 101 (11), 4220-4227.

390

(33)

Sholts, S. B.; Wärmländer, S. K. T. S.; Flores, L. M.; Miller, K. W. P.; Walker, P. L.

391

Variation in the Measurement of Cranial Volume and Surface Area Using 3D Laser Scanning

392

Technology. J. Forensic Sci. 2010, 55 (4), 871-876.

393

(34)

Verdolotti, L.; Lavorgna, M.; Lamanna, R.; Di Maio, E.; Iannace, S.

394

Polyurethane-silica hybrid foam by sol–gel approach: Chemical and functional properties.

395

Polymer 2015, 56, 20-28.

396

(35)

Hassanajili, S.; Masoudi, E.; Karimi, G.; Khademi, M. Mixed matrix membranes

397

based on polyetherurethane and polyesterurethane containing silica nanoparticles for

398

separation of CO2/CH4 gases. Sep. Purif. Technol. 2013, 116, 1-12.

399 400

(36)

Pingan, H.; Mengjun, J.; Yanyan, Z.; Ling, H. A silica/PVA adhesive hybrid material

with high transparency, thermostability and mechanical strength. RSC Advances 2017, 7 (5),



401 402

2450-2459. (37)

Serkis, M.; Poręba, R.; Hodan, J.; Kredatusová, J.; Špírková, M. Preparation and

403

characterization of thermoplastic water ‐ borne polycarbonate ‐ based polyurethane

404

dispersions and cast films. J. Appl. Polym. Sci. 2015, 132 (42).

405 406 407

(38)

Wu, S.-H.; Mou, C.-Y.; Lin, H.-P. Synthesis of mesoporous silica nanoparticles.

ChSRv 2013, 42 (9), 3862-3875. (39)

Ho, L.; Cuppok, Y.; Muschert, S.; Gordon, K. C.; Pepper, M.; Shen, Y.; Siepmann, F.;

408

Siepmann, J.; Taday, P. F.; Rades, T. Effects of film coating thickness and drug layer

409

uniformity on in vitro drug release from sustained-release coated pellets: A case study using

410

terahertz pulsed imaging. Int. J. Pharm. 2009, 382 (1), 151-159.

411

(40)

Strawhecker, K. E.; Kumar, S. K.; Douglas, J. F.; Karim, A. The Critical Role of

412

Solvent Evaporation on the Roughness of Spin-Cast Polymer Films. Macromolecules 2001,

413

34 (14), 4669-4672.

414

(41)

Han, Y.; Chen, Z.; Dong, W.; Xin, Z. Improved water resistance, thermal stability,

415

and mechanical properties of waterborne polyurethane nanohybrids reinforced by fumed silica

416

via in situ polymerization. HPP 2015, 27 (7), 824-832.

417

(42)

Hassanajili, S.; Sajedi, M. T. Fumed silica/polyurethane nanocomposites: effect of

418

silica concentration and its surface modification on rheology and mechanical properties.

419

Iranian Polymer Journal 2016, 25 (8), 697-710.

420

(43)

Sankar, S.; Sanjeev, S.; Sharma, D. Synthesis and characterization of mesoporous

421

SiO2 nanoparticles synthesized from Biogenic Rice Husk Ash for optoelectronic applications.

422

An International Journal of Engineering Sciences 2016, 17, 353-358.

423

(44)

Wang, X.; Dou, L.; Li, Z.; Yang, L.; Yu, J.; Ding, B. Flexible hierarchical ZrO2

424

nanoparticle-embedded SiO2 nanofibrous membrane as a versatile tool for efficient removal

425

of phosphate. ACS applied materials & interfaces 2016, 8 (50), 34668-34676.


Page 18 of 30

Page 19 of 30

426


(45)

Yang, Y.; Wei, Z.; Wang, C.; Tong, Z. Versatile fabrication of nanocomposite

427

microcapsules with controlled shell thickness and low permeability. ACS applied materials &

428

interfaces 2013, 5 (7), 2495-2502.

429

(46)

ISO Fertilizers and soil conditioners —Controlled-release fertilizer —General

430

requirements. The International Organization for Standardization: Switzerland, 2016; Vol.

431

ISO 18644:2016(E).

432

(47)

Cai, D.; Wang, L.; Zhang, G.; Zhang, X.; Wu, Z. Controlling pesticide loss by natural

433

porous micro/nano composites: straw ash-based biochar and biosilica. ACS applied materials

434

& interfaces 2013, 5 (18), 9212-9216.

435



Page 20 of 30

436

Table captions

437

Table 1. Physical properties of urea prills and Large Tablets Urea (LTUs).

438

Table 2. Composition of various coated fertilizers.

439 440

Figure captions

441

Figure 1. Three-dimensional scanning images of urea prill (a1) and Large Tablet Urea (LTU)

442

(b1) and scanning electron microscopy (SEM) images of urea prill (a2, 30×; a3, 200×) and

443

LTU (b2, 30×; b3, 200×).

444

Figure 2. (A) Photograph of coating materials: bio-polyol (a), bio-polyol mixed with Nano

445

Fumed Silica (NFS) particles (b), Methylene diphenyl diisocyanate (MDI) (c) and MDI mixed

446

with NFS particles (d). (B) Schematic diagram of the synthesis of Large Tablet

447

Controlled-Release Urea (LTCRU) and Modified Large Tablet Controlled-Release Urea

448

(MLTCRU). (C) Photograph of conventional urea pills (U), Large Tablet Urea (LTU), Large

449

Tablet Controlled-Release Urea (LTCRU) and Modified Large Tablet Controlled-Release

450

Urea (MLTCRU).

451

Figure 3. Fourier Transform Infrared (FTIR) spectra of bio-based polyol (a), Methylene

452

diphenyl diisocyanate (MDI) (b), coatings of Large Tablet Controlled-Release Urea (LTCRU)

453

(c) and Modified Large Tablet Controlled-Release Urea (MLTCRU) (d).

454

Figure 4. Scanning electron microscopy coupled with energy dispersive X-ray Spectroscopy

455

(SEM-EDS) images and corresponding water contact angles of surfaces of Large Tablet

456

Controlled-Release

457

Controlled-Release Urea 1 (MLTCRU1) (b1, 200×), and cross sections of LTCRU1 (a3,

458

2,000×) and MLTCRU1 (b3, 2,000×). EDS spectra of LTCRU1 surface (a2), EDS spectra of

459

MLTCRU1 surface (b2), EDS spectra of cross section of LTCRU1 (a4) and EDS spectra of

460

cross section of MLTCRU1 (b4).

Urea

1

(LTCRU1)

(a1,

200×)


and

Modified

Large

Tablet

Page 21 of 30


461

Figure 5. Nitrogen release characteristics of Large Tablet Controlled-Release Urea 1

462

(LTCRU1) (a), LTCRU2 (b), Modified Large Tablet Controlled-Release Urea 1 (MLTCRU1)

463

(c) and MLTCRU2 (d) at 25 °C in deionized water. (a, y = 11.98ln(x) + 39.44, with R2 =

464

0.8340; b, y = 0.67x + 1.99, with R2 = 0.9967; c, y = 10.51ln(x) + 31.88, with R2 = 0.8487; d,

465

y = 0.60x - 1.82, with R2 = 0.9727).

466

Figure 6. Relationship between nitrogen (N) release rates (%) and volume change (%) of

467

Large Tablet Controlled-Release Urea (LTCRU) at four stages (a, b, c, and d) of the pattern

468

one. The top photo showed the actual sizes of LTCRU at these stages: initial dissolution stage

469

(a, 0-3rd day, no volume change), fast dissolution stage (b, 3-10th day, no volume change),

470

slow dissolution stage (c, 10-28th day, no volume change) and final stage (d, after 28th day,

471

no volume change). The figure on the bottom showed measured fertilizer volumes: a, 100%, b,

472

100%, c, 100%, and d, 100%. at four stages.

473


474

Modified Large Tablet Controlled-Release Urea (MLTCRU) at four stages (a, b, c, and d) of

475

the pattern two. The top photo showed the actual sizes of MLTCRU at these stages: wetting

476

stage (a, 0-3rd day, no volume change), dissolution stage (b, 3-14th day, larger), swelling

477

stage (c, 14-28th day, largest) and final stage (d, after 27th day, decreased). The figure on the

478

bottom showed measured fertilizer volumes: a, 100%, b, 100-106%, c, 106-111%, and d,

479

111-106%. at four stages.



480

Page 22 of 30

Table 1. Physical properties of urea prills and Large Tablets Urea (LTUs). Mass (g)

Volume (mm3)

Surface area (mm2)

Surface area-to-weight ratio (mm2 g-1)

Urea prills

0.03±0.01

26.35±5.09

43.65±7.88

1257.78

LTUs

2.00±0.15

1726.25±32.45

733.63±50.39

359.36

481 482

Table 2. Composition of various coated fertilizers. Fertilizers LTCRU1 LTCRU2

β

β

MLTCRU1 MLTCRU2

γ

γ

Design of coating content

Actual coating content

Total N α

(wt. %)

(wt. %)

(wt. %)

2

2.05±0.06

45.25±0.06

3

3.04±0.15

44.80±0.15

2

1.83±0.11

45.35±0.11

3

2.87±0.12

44.87±0.12

α

the total Nitrogen (N) content was calculated based on the actual coating content.

β

LTCRU: Large Tablet Controlled-Release Urea.

γ

MLTCRU: Modified Large Tablet Controlled-Release Urea.

483


Page 23 of 30


484 485

Figure 1. Three-dimensional scanning images of urea prill (a1) and Large Tablet Urea (LTU)

486

(b1) and scanning electron microscopy (SEM) images of urea prill (a2, 30×; a3, 200×) and

487

LTU (b2, 30×; b3, 200×).



488 489

Figure 2. (A) Photograph of coating materials: bio-polyol (a), bio-polyol mixed with Nano

490

Fumed Silica (NFS) particles (b), Methylene diphenyl diisocyanate (MDI) (c) and MDI

491

mixed with NFS particles (d). (B) Schematic diagram of the synthesis of Large Tablet

492

Controlled-Release Urea (LTCRU) and Modified Large Tablet Controlled-Release Urea

493

(MLTCRU). (C) Photograph of conventional urea pills (U), Large Tablet Urea (LTU), Large

494

Tablet Controlled-Release Urea (LTCRU) and Modified Large Tablet Controlled-Release

495

Urea (MLTCRU).


Page 24 of 30

Page 25 of 30


496 497

Figure 3. Fourier Transform Infrared (FTIR) spectra of bio-based polyol (a), Methylene

498

diphenyl diisocyanate (MDI) (b), coatings of Large Tablet Controlled-Release Urea (LTCRU)

499

(c) and Modified Large Tablet Controlled-Release Urea (MLTCRU) (d).



Page 26 of 30

500 501

Figure 4. Scanning electron microscopy coupled with energy dispersive X-ray Spectroscopy

502

(SEM-EDS) images and corresponding water contact angles of surfaces of Large Tablet

503

Controlled-Release

504

Controlled-Release Urea 1 (MLTCRU1) (b1, 200×), and cross sections of LTCRU1 (a3,

505

2,000×) and MLTCRU1 (b3, 2,000×). EDS spectra of LTCRU1 surface (a2), EDS spectra of

Urea

1

(LTCRU1)

(a1,

200×)


and

Modified

Large

Tablet

Page 27 of 30


506

MLTCRU1 surface (b2), EDS spectra of cross section of LTCRU1 (a4) and EDS spectra of

507

cross section of MLTCRU1 (b4).

508

100

a

Nitrogen accumulative release (%)

c

b

80 d

60 a - LTCRU1 b - LTCRU2 c - MLTCRU d - MLTCRU2

40

a: b: c: d:

20

y y y y

= = = =

11.98ln(x) + 39.44 0.67x + 1.99 10.51ln(x) + 31.88 0.60x - 1.82

R2 = 0.8340 R2 = 0.9967 R2 = 0.8487 R2 = 0.9727

0 0

10

20

30

40

50

60

70

80

90

100 110 120 130 140

509

Incubation time (days)

510

Figure 5. Nitrogen release characteristics of Large Tablet Controlled-Release Urea 1

511

(LTCRU1) (a), LTCRU2 (b), Modified Large Tablet Controlled-Release Urea 1 (MLTCRU1)

512

(c) and MLTCRU2 (d) at 25 °C in deionized water. (a, y = 11.98ln(x) + 39.44, with R2 =

513

0.8340; b, y = 0.67x + 1.99, with R2 = 0.9967; c, y = 10.51ln(x) + 31.88, with R2 = 0.8487; d,

514

y = 0.60x - 1.82, with R2 = 0.9727).



515 516


517

Large Tablet Controlled-Release Urea (LTCRU) at four stages (a, b, c, and d) of the pattern

518

one. The top photo showed the actual sizes of LTCRU at these stages: initial dissolution stage

519

(a, 0-3rd day, no volume change), fast dissolution stage (b, 3-10th day, no volume change),

520

slow dissolution stage (c, 10-28th day, no volume change) and final stage (d, after 28th day,

521

no volume change). The figure on the bottom showed measured fertilizer volumes: a, 100%, b,

522

100%, c, 100%, and d, 100% at four stages.


Page 28 of 30

Page 29 of 30


523 524


525

Modified Large Tablet Controlled-Release Urea (MLTCRU) at four stages (a, b, c, and d) of

526

the pattern two. The top photo showed the actual sizes of MLTCRU at these stages: wetting

527

stage (a, 0-3rd day, no volume change), dissolution stage (b, 3-14th day, larger), swelling

528

stage (c, 14-28th day, largest) and final stage (d, after 27th day, decreased). The figure on the

529

bottom showed measured fertilizer volumes: a, 100%, b, 100-106%, c, 106-111%, and d,

530

111-106% at four stages.



For Table of contents use only Bio-based Large Tablet Controlled-Release Urea: Synthesis, Characterization, and Controlled-Released Mechanisms

TOC (ART) 531

Modified bio-based material improved the slow-release properties of LTCRU by reducing

532

surface area-to-weight ratio and generating two nitrogen release patterns.


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Bio-based Large Tablet Controlled-Release Urea: Synthesis

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