Water Retention Ratio Research Articles

Robinia pseudoacacia Quickly Adjusts Its Water Uptake after Rainfall in Seasonally Dry Regions

Precipitation is a key factor affecting plant growth and development in seasonally arid regions. However, most of the traditional hydrological methods mainly select typically sunny days for sampling, and the immediate water absorption strategy of plants during and after rainfall is still unclear. This study used stable hydrogen and oxygen isotope technology to study the soil moisture absorption rates of Robinia pseudoacacia and the soil moisture content at different soil layers at different sampling times (0, 6, 12, 18 and 24 h) after rainfall. The results showed that the moisture content of the shallow soil layer decreased, while that of the deep soil layer increased over time after rainfall. R. pseudoacacia mainly utilized water from the 0–20 and 20–40 cm soil layers at 6 h after rainfall, which accounted for 36.52% and 22.25% of the rainfall, respectively. At 24 h, the 40–60, 60–80 and 80–100 cm soil layers contributed 25.25%, 18.44% and 24.45% of the water content, respectively. The shallow soil layer retained more rainfall within 6 h after rain fell, and the water retention ratio of the medium–shallow soil layer (0–60 cm) increased to 48.4%, retaining more water at 14–20 h. At 12 h, the medium–shallow soil layer (0–60 cm), runoff and groundwater constituted 37.1%, 14.4% and 15.7% of the precipitation, respectively, and rainfall retained in the deep soil layer (60–100 cm) accounted for 32.8%. In summary, R. pseudoacacia tends to use a large amount of shallow soil water in seasonally arid regions when precipitation supplements the surface soil moisture content and it utilizes deep soil water when the rainfall infiltrates and recharges the deep soil layer. Since R. pseudoacacia is sensitive to precipitation, it can quickly adjust its water absorption depth range during the short-term rainfall period to absorb as much precipitation as possible.

Synthesis and characterization of allyl mannitol cross-linker based novel hydrogel for capturing of toxic metal ions from aqueous solution

ABSTRACT Three grades of allyl-mannitol cross-linker-based hydrogel (AMCLHs hydrogel) have been synthesized with the help of acrylic acid and acrylamide monomers using a free radical co-polymerization technique. The three prepared grades of AMCLHs hydrogel have been referred to as AMCLHs-1, AMCLHs-2, and AMCLHs-3, respectively. The prepared AMCLHs hydrogels have been characterized by several analytical techniques viz. Fourier transform infrared (FTIR) spectroscopy, thermogravimetric (TG) analysis, point of zero charge (ΔpHPZC), analysis, and scanning electron microscope (SEM) analysis, respectively. The synthesized hydrogels have been utilized for the elimination of Cu2+ and Co2+ ions from wastewater. The properties of prepared AMCLHs hydrogels, i.e. swelling and water retention ratio have been studied in distilled water under optimized conditions. The maximum swelling ratio of the best grade of hydrogel (AMCLHs-1) has been found to be 400.5 g/g with the water retention ratio of 75.09% during 24 h. These findings indicate the AMCLHs-1 hydrogel has remarkable swelling and water retention capacity. The maximum metal ion removal efficiency of AMCLHs-1 hydrogel from aqueous solutions has been found to be 96.6% for Cu2+ and 94.2% for Co2+ ions under optimum conditions. The experimental data fitted well with the Langmuir and Freundlich adsorption models, revealing maximum adsorption capacities of 431.03 mg/g for Cu2+ ions and 414.93 mg/g for Co2+ ions, respectively. In addition, the rate for the adsorption of Cu2+ and Co2+ ions onto AMCLHs-1 hydrogel follows both Pseudo first and second-order kinetic models. The negative ΔG values indicate that the adsorption process occurs spontaneously, while positive ΔH values suggest that the adsorption process is exothermic in nature. The prepared AMCLHs hydrogel is reusable and exhibits high desorption efficiency with 87.63% for Cu2+ and 85.21% for Co2+ metal ions even after the fourth cycle. Overall, AMCLHs hydrogel is a cost-effective and reusable adsorbent that possesses a significant potential for heavy metal ion removal from aqueous solutions.

Synthesis and characterization of novel D‐mannitol based hydrogel: Swelling and adsorption behavior of heavy metal ion studies

AbstractA highly efficient hydrogel derived from D‐Mannitol xanthate has been successfully synthesized using a free‐radical solution copolymerization technique. An equimolar mixture of acrylonitrile (AN) and acrylic acid (AA) has been reacted with D‐Mannitol xanthate (DMX) under inert atmosphere. Three distinct grades of D‐Mannitol xanthate‐based hydrogels viz. DMXHGs‐1, DMXHGs‐2, and DMXHGs‐3, were prepared. Extensive analyses were conducted on the hydrogels using various methods such as UV, FT‐IR, SEM, XRD, GPC, TGA and ΔpHPZC. The maximum swelling ratio of DMXHGs‐3 was found to be 52122%, 50434% and 48576% for 24 h with water retention ratio of 80.98%, 78.64% and 79.22% for 30 h in distilled, tap and gray water respectively. These findings indicate the DMXHGs‐3 hydrogel has remarkable swelling and water retention capacity. Comprehensive investigations were carried out to evaluate the hydrogel's remarkable adsorption capacity to act as an adsorbent for effectively removing hazardous metal ions. The highest removal percentages of 95.5% and 94.4% and maximum adsorption capacities of 523.56 mg g−1 and 462.96 mg g−1 were observed with DMXHGs‐3 hydrogel for Cu2+ and Co2+ ions, respectively. Metal ion removal experiments were conducted by varying several parameters including dosage, pH, temperature, concentration, and time. The quantification of Cu2+ and Co2+ was accomplished using UV–visible spectroscopy. Present studies demonstrate the suitability of D‐mannitol xanthate‐based hydrogels for the efficient removal of toxic metal ions from wastewater.

Synthesis of Hydrogel Based on Poly (Acrylic Acid–Co‐Vinyl Acetate) Grafted on Modified Recycled Cellulose for Use in Fertilizer Slow‐Release System

The aim of this work is a synthesis of suitable hydrogel to produce slow‐release fertilizer using recycled cellulose which is obtained from waste paper. For this purpose, initially, we extracted alpha cellulose from waste paper and modified it to obtain carboxymethyl cellulose (CMC). Then, the CMC was converted to a suitable hydrogel through in situ graft copolymerization of acrylic acid and vinyl acetate in the presence of methylene bisacrylamide as a crosslinker. The various factors that affect hydrogel synthesis, such as the amounts of CMC, monomers, initiator, and crosslinker, were evaluated. In the optimized formulation, the weight ratio of monomers to CMC is 7, the molar ratio of monomers to each other is 1, and the crosslinker is used as 3 molar percent of monomers. The products were characterized using Fourier transform infrared, thermal gravimetric analysis, and scanning electron microscope analyses. The swelling behavior of the synthesized hydrogels was evaluated in different environments, such as distilled water, tap water, salt water, and different pH levels. The swelling ratio increases with an increase in pH level. Between the synthesized hydrogels, the best one was selected for slow‐release fertilizer production and loaded with 20‐20‐20 fertilizer (NPK), and the release behavior was evaluated. In an alkaline pH, there was a long time for NPK release within a slow‐release medium and even after 361 h, the release process was continued. Also, the performance of the fertilizer‐loaded hydrogel in soil using water holding capacity and water retention ratio tests were evaluated.

Measurement of Water Retention Ratio in Rust Layer by Electrical Resistance

Measurement of Water Retention Ratio in Rust Layer by Electrical Resistance

Synthesis of tapioca starch/palm oil encapsulated urea-impregnated biochar derived from peppercorn waste as a sustainable controlled-release fertilizer

Nutrient leaching and volatilization cause environmental pollution, thus the pursuit of developing controlled-release fertilizer formulation is necessary. Biochar-based fertilizer exhibits slow-release characteristic, however the nutrient release mechanism needs to be improved. To overcome this limitation, the approach of applying encapsulation technology with biochar-based fertilizer has been implemented in this study. Black peppercorn waste was used to synthesize urea-impregnated biochar (UIB). Central composite design was used to investigate the effects of pyrolysis temperature, residence time and urea:biochar ratio on nitrogen content of UIB. The optimum condition to synthesize UIB was at 400 °C pyrolysis temperature, 120 min residence time and 0.6:1 urea:biochar ratio, which resulted in 16.07% nitrogen content. The tapioca starch/palm oil (PO) biofilm formulated using 8 g of tapioca starch and 0.12 µL of PO was coated on the UIB to produce encapsulated urea-impregnated biochar (EUIB). The UIB and EUIB pellets achieved complete release of nitrogen in water after 90 min and 330 min, respectively. The nutrient release mechanism of UIB and EUIB was best described by the Higuchi model and Korsmeyer-Peppas model, respectively. The improvement of water retention ratio of UIB and EUIB pellets was more significant in sandy-textural soil as compared to clayey-textural soil. The EUIB derived from peppercorn waste has the potential to be utilized as a sustainable controlled-release fertilizer for agriculture.

Nontoxic chemical crosslinked bacterial cellulose-heparin-gelatin composite hydrogel as antibacterial dressing

A hydrogel dressing based on bacterial cellulose (BC), which is grafted with quaternary ammonium functional and crosslinked with the gelatin-heparin system, is prepared to provide the features mainly concerning softness, high swelling ratio, antibacterial property, and biocompatibility. An innovation of preparation is that the BC is beaten into short-chain scaffolds to improve the efficiency of grafting, which not only simplifies the preparation process but also avoids the biotoxicity caused by the introduction of toxic catalyst such as dimethyl sulfoxide (DMSO) or uncertain toxic side products in long-chain grafting. Scanning electron microscopy (SEM) shows that the QBC/Hep/Gel composite hydrogel possesses a three-dimensional mesh structure with high porosity. The hydrogel shows outstanding water management performance indicated by the swelling ratio of 1476%, water retention ratio of more than 90% at 120 h, and moisture permeability of 3296 g m−2 24 h−1. The antibacterial experiment is implemented with staphylococcus aureus, and the antibacterial effect is represented by an inhibition zone of 3 cm in diameter. In vivo animal experiments suggested that QBC/Hep/Gel could effectively promote epithelial reconstruction, collagen deposition, and angiogenesis in normal wounds, reduce inflammation, and accelerate wound healing. All these results indicate that the proposed QBC/Hep/Gel hydrogel is a potential composite for antibacterial dressing.

A self-healable and bioadhesive acacia gum polysaccharide-based injectable hydrogel for wound healing acceleration.

The present study aimed at developing an injectable hydrogel based on acacia gum (AG) for wound healing acceleration. The hydrogels were synthetized through metal-ligand coordination mediated by Fe3+ and characterized in terms of gelation time, gel content, initial water content, swelling capacity, water retention ratio, and porosity. Moreover, FTIR, XRD and TGA analyses were performed for the hydrogels and allantoin (Alla) loaded ones. Furthermore, bioadhessiveness, and self-healing as well as antibacterial, toxicity and wound healing potentials of the hydrogels were evaluated. The hydrogels displayed fast gelation time, high swelling, porosity, and bioadhessiveness, as well as antioxidant, self-healing, antibacterial, blood clotting, and injectability properties. FTIR, XRD and TGA analyses confirmed hydrogel synthesis and drug loading. The Alla-loaded hydrogels accelerated wound healing by decreasing the inflammation and increasing the cell proliferation as well as collagen deposition. Hemocompatibility, cell cytotoxicity, and in vivo toxicity experiments were indicative of a high biocompatibility level for the hydrogels. Given the advantages of fast gelation, injectability and beneficial biological properties, the use of Alla-loaded hydrogels could be considered a new remedy for efficient wound healing.

Co-incorporation of hydrotalcite and starch into biochar-based fertilizers for the synthesis of slow-release fertilizers with improved water retention

The unsatisfactory nutrient slow-release and water-retention performance of traditional biochar-based compound fertilizers (BCF) severely limit their practical application. Herein, a new type of slow-release fertilizer with high water retention was fabricated via the incorporation of hydrotalcite and starch into BCF, named as HS-BCF. The water-retention and nutrient releasing performance of the prepared HS-BCF and related nutrient slow-release mechanism were investigated. The results showed that the incorporation of hydrotalcite and starch into BCF could increase the soil water-retention ratio by 5–10% points. The accumulated N, P, and K leaching amounts of HS-BCF in soil within 30 days were 49.4%, 13.3%, and 87.4% of BCF at most, respectively. Kinetic analysis indicated that the release of nutrients from HS-BCF was attributed to the coupling of the diffusion-controlled and relaxation-controlled mechanism. Moreover, hydrotalcite could bind with P in HS-BCF, contributing to the enhanced durability of P in HS-BCF. Finally, pot experiments showed that the N–P–K utilization efficiencies of HS-BCF were all higher than those of BCF due to a better synchronization between the nutrient release of HS-BCF and the uptake of tomato plants. Overall, the study may provide a promising strategy for simultaneously improving the water-retention and slow-release performance of traditional biochar-based fertilizers.Graphical

High-Strength, High-Water-Retention Hemicellulose-Based Hydrogel and Its Application in Urea Slow Release.

The use of fertilizer is closely related to crop growth and environmental protection in agricultural production. It is of great significance to develop environmentally friendly and biodegradable bio-based slow-release fertilizers. In this work, porous hemicellulose-based hydrogels were created, which had excellent mechanical properties, water retention properties (the water retention ratio in soil was 93.8% after 5 d), antioxidant properties (76.76%), and UV resistance (92.2%). This improves the efficiency and potential of its application in soil. In addition, electrostatic interaction and coating with sodium alginate produced a stable core-shell structure. The slow release of urea was realized. The cumulative release ratio of urea after 12 h was 27.42% and 11.38%, and the release kinetic constants were 0.0973 and 0.0288, in aqueous solution and soil, respectively. The sustained release results demonstrated that urea diffusion in aqueous solution followed the Korsmeyer-Peppas model, indicating the Fick diffusion mechanism, whereas diffusion in soil adhered to the Higuchi model. The outcomes show that urea release ratio may be successfully slowed down by hemicellulose hydrogels with high water retention ability. This provides a new method for the application of lignocellulosic biomass in agricultural slow-release fertilizer.

Lignin particles as green pore-forming agents for the fabrication of microporous polysulfone membranes

Templating polymeric membranes with micro-nano-scaled solid materials is an effective method to simultaneously improve the water flux and retention ratio. However, the fabrication of a green, recyclable, and size-controlled template material remains a challenge. Here, a new green pore-forming agent, lignin particles (LP), was developed to prepare porous polysulfone (PSF) membranes via the phase inversion technique. A series of LP have uniform sizes from ~200 nm to ~1800 nm. The performances of the templated PSF membranes cast at different sizes and contents of LP were examined for their surface and crosssection morphologies. The LP-templated PSF membranes displayed a remarkable enhancement in flux, porosity, and moisture content. Particularly, the PSF membranes cast with LP from ~200 to 1800 nm broke the traditional trade-off to a certain degree, which possessed stable retentions of bovine serum albumin (> 85 %) and significantly improved water flux (174.275 to 254.775 L m−2 h−1). In addition, the LP pore-forming agent is low-cost and environmentally friendly as it was prepared from industrial by-products and can be easily recycled. Overall, this study shows that lignin particles are green pore-forming agents that can be used for the fabrication of porous polymeric membranes with improved performance for water treatment.

Preparation and properties of Sanxan gel based fertilizer for water retention and slow-release

The advent of gel fertilizers has benefited agriculture and the environment. This study utilized sanxan, a novel polysaccharide, as a carrier and loaded it with urea to create sanxan gel fertilizer (SGF), thus creating a new, effective gel fertilizer. Water retention and sustained release ability of SGF were evaluated, and crop experiments were carried out. The results showed that, SGF that content 2.0 % solution of sanxan and loaded 20 g g−1 of urea were prepared by heating-cooling method. The water-retention ratio of SGF was attained at 56.4 g g−1 for 10 h. The urea releases of SGF in water have a more significant persistence than pure urea. In addition, wheat growth was promoted by SGF, compared with pure urea, the biomass of wheat shoot and root increased 27.4 % and 62.2 % during 20 days, respectively. Consequently, SGF has the ability to retain water and slowly release nutrition, which was an ideal carrier for managing water and urea. The SGF developed in this study provides data support and theoretical basis for the application of sanxan gel in agriculture and the environment.

Abundant tannic acid modified gelatin/sodium alginate biocomposite hydrogels with high toughness, antifreezing, antioxidant and antibacterial properties

The acidity of high tannic acid (TA) content solution can destroy the structure of protein, such as gelatin (G). This causes a big challenge to introduce abundant TA into the G-based hydrogels. Here, the G-based hydrogel system with abundant TA as hydrogen bonds provider was constructed by a “protective film” strategy. The protective film around the composite hydrogel was first formed by the chelation of sodium alginate (SA) and Ca2+. Subsequently, abundant TA and Ca2+ were successively introduced into the hydrogel system by immersing method. This strategy effectively protected the structure of the designed hydrogel. After treatment with 0.3 w/v TA and 0.06 w/v Ca2+ solutions, the tensile modulus, elongation at break and toughness of G/SA hydrogel increased about 4-, 2-, and 6-fold, respectively. Besides, G/SA-TA/Ca2+ hydrogels exhibited good water retention, anti-freezing, antioxidant, antibacterial properties and low hemolysis ratio. Cell experiments showed that G/SA-TA/Ca2+ hydrogels possessed good biocompatibility and could promote cell migration. Therefore, G/SA-TA/Ca2+ hydrogels are expected to be used in the field of biomedical engineering. The strategy proposed in this work also provides a new idea for improving the properties of other protein-based hydrogels.

Experimental Study for the Cementation Effect of Dust Soil by Using Soybean Urease

Dust is an environmental and health hazard. In this study, a new technology for dust suppressant is introduced using soybean urease with an optimal cementing solution. Calcium carbonate is produced by soybean urease and cementing solution, which bonds the soil particles towards a dust suppressant. A laboratory wind tunnel test is carried out to examine its effectiveness and discover possible optimization solutions. Several factors, including soybean meal concentration, cementing solution concentration, and volume of solution per unit area, are examined to quantify their influences on soil transport mass, evaporation ratio, evaporation rate, surface strength, water retention ratio, and infiltration rate of soil treated by different dust suppressants. Field tests are conducted to explore the performance of this method in the natural environment. The results show that compared with other dust suppressants, the optimized soybean urease has the smallest evaporation rate, a moderate infiltration rate, the largest water retention ratio and surface strength. The indexes of soybean urease for dust suppressant are found to be better than traditional materials. In the natural environment, soybean urease has a stronger anti-disturbance ability. This study concludes that soybean urease dust suppressant has great application potential as a cheap and green method.

Sustained release of alginate hydrogel containing antimicrobial peptide Chol-37(F34-R) in vitro and its effect on wound healing in murine model of Pseudomonas aeruginosa infection.

Antibiotic resistance is a significant public health concern around the globe. Antimicrobial peptides exhibit broad-spectrum and efficient antibacterial activity with an added advantage of low drug resistance. The higher water content and 3D network structure of the hydrogels are beneficial for maintaining antimicrobial peptide activity and help to prevent degradation. The antimicrobial peptide released from hydrogels also hasten the local wound healing by promoting epithelial tissue regeneration and granulation tissue formation. This study aimed at developing sodium alginate based hydrogel loaded with a novel antimicrobial peptide Chol-37(F34-R) and to investigate the characteristics in vitro and in vivo as an alternative antibacterial wound dressing to treat infectious wounds. Hydrogels were developed and optimized by varying the concentrations of crosslinkers and subjected to various characterization tests like cross-sectional morphology, swelling index, percent water contents, water retention ratio, drug release and antibacterial activity in vitro, and Pseudomonas aeruginosa infected wound mice model in vivo. The results indicated that the hydrogel C proved superior in terms of cross-sectional morphology having uniformly sized interconnected pores, a good swelling index, with the capacity to retain a higher quantity of water. Furthermore, the optimized hydrogel has been found to exert a significant antimicrobial activity against bacteria and was also found to prevent bacterial infiltration into the wound site due to forming an impermeable barrier between the wound bed and external environment. The optimized hydrogel was found to significantly hasten skin regeneration in animal models when compared to other treatments in addition to strong inhibitory effect on the release of pro-inflammatory cytokines (interleukin-1β and tumor necrosis factor-α). Our results suggest that sodium alginate -based hydrogels loaded with Chol-37(F34-R) hold the potential to be used as an alternative to conventional antibiotics in treating infectious skin wounds.

Itaconic acid–urea–acrylic acid copolymer as a novel water and nutrient retaining fertilizer

To meet the demands of a growing population, the global food production will have to increase by at least 70% by 2050. Developing high-performance water and nutrient retaining fertilizer (WNRF) to increase crop yield in arid and semi-arid areas is an effective measure to maintain the balance of ecological environment and the sustainable development of human being. In this study, itaconic acid, as one of the 12 most promising bio-based platform compounds, was combined with urea and acrylic acid in methanol to form the oligomer, which could quickly cross-link to obtain a new type of WNRF with the rapid evaporation of methanol. According to the performance of water and fertilizer retention, the optimal WNRF showed water retention ratio of 47.1%, migrate-to-surface loss control ratio of 85.6%, and leaching loss control ratio of 66.6%, respectively. It retained in the soil via the filtering effect, resulting in lower loss of water and nutrient. As illustrated by two individual pot experiments, the optimal WNRF effectively facilitated the growth of plant rape and maize, in which the dry matter weight of shoot was increased by 28% and 88% compared to the control group. This work provides a promising approach to enhance the utilization efficiency of water and nutrient, which is expected to have potential applications in sustainable modern agriculture of drought regions.

Hydroxypropyl Chitosan/Soy Protein Isolate Conduits Promote Peripheral Nerve Regeneration.

Designing scaffolds, with optimized microstructure and function for promoting the release of neuro-related factors, is significant in peripheral nerve regeneration. Herein, a series of hydroxypropyl chitosan/soy protein isolate composite sponges (HCSS) were fabricated by a freeze-drying technique. The physicochemical properties of the resultant HCSS were examined by a Fourier infrared spectrometer, X-ray diffractometer, scanning electron microscope, water absorption assay, water retention assay, and compressive strength assay. The results indicated that HCSS exhibited an interconnected porous microstructure and a high water retention ratio with the increase in soy protein isolate (SPI) content. The biological characterization found that the HCSS-50 containing 50% SPI content profoundly promoted the proliferation of RSC96 cells and the secretion of neuro-related factors without excessive reactive oxygen species production. In addition, HCSS-50 could significantly promote the expression of neuro-related factors; for example, the expression of TGF-β was three times higher than that of the control group. Finally, an optimized HCSS-based conduit was fabricated from HCSS-50 to repair sciatic nerve injury in rats with the combination of bone marrow mesenchymal stem cells (BMSCs) or BMSC-derived Schwann cells (SCs). The results suggested that the constructed HCSS-based conduit accompanying BMSC-derived SCs could effectively promote axonal regeneration and upregulate the expression of neuro-related factors such as Krox20, Zeb2, and GAP43. Collectively, a newly engineered nerve conduit system was developed by incorporating HCSS-50 and BMSC-derived SCs, which could be an alternative candidate for peripheral nerve regeneration. Impact statement Peripheral nerve repair is of paramount significance in the clinical. This work describes a hydroxypropyl chitosan/soy protein isolate conduit, which could effectively promote axonal regeneration and upregulate the expression of neuro-related factors. Thus, we provide a potential candidate for peripheral nerve regeneration.

New mixture design approach to paper sludge ash-based stabilizers for treatment of potential irrigation earth dam materials with high water contents

In those cases where construction-generated soils with high water contents are used as filling or embankment materials, it is sometimes difficult to satisfy the specified compaction degrees. Recently, soil stabilization using a paper sludge ash-based stabilizer (PSAS) has been developed. Paper sludge (PS) ash is waste generated by the incineration of PS discharged from paper mills. It has been found that PS ash can absorb and retain excess water; and therefore, PS ash can simultaneously improve the stability of muds when it is mixed with them. However, the current mixture design approach for PSAS-treated soils is only applicable to muds with water contents exceeding the liquid limits and cannot be applied to construction-generated soils in which the coarse fraction is dominant. Therefore, this study evaluated the effects of a PSAS on the compaction and mechanical characteristics of coarse-grained soils to use them as materials for irrigation earth dams. A series of compaction tests were conducted on two types of soil samples treated with a PSAS to investigate its effects on the compaction characteristics. The compaction characteristics obtained from the tests were assessed considering the water absorption and retention performance of the PSAS. It was found that the modified optimum water content w*opt of the treated samples, which was evaluated using the amount of water unabsorbed and unretained by the PSAS, was almost equal to the wopt of the untreated samples. Consequently, a new mixture design approach was proposed based on the compaction characteristics. The calculated results successfully demonstrated that, if the compaction curve of an untreated sample and the water absorption and retention ratio, Wab, of the PSAS corresponding to a certain curing period are obtained, the range in the PSAS addition amount, APS1m3, required to attain the targeted compaction degree, (Dc)target, for the curing period can be estimated without conducting compaction tests on the treated samples. Finally, the strength characteristics of the treated samples prescribed by the proposed mixture design method were investigated by conducting CBR tests and CU¯TC tests. Based on the test results, discussions were made on the contribution of the proposed mixture design to the strength development of the treated samples and on the development mechanism.

Formulation and characterization of water retention and slow-release urea fertilizer based on Borassus aethiopum starch and Maesopsis eminii hydrogels

Environmentally friendly slow-release fertilizers (SRF) based on Borassus aethiopum starch (BAS-SRF) and Maesopsis eminii (ME-SRF) hydrogels were formulated by encapsulating urea into biomaterials using borax as a binder. The SRFs were characterized by FT-IR, SEM and XRD techniques. The gel ratios of the hydrogels were found to be 71.27 ± 0.31 and 57.43 ± 2.27 for BAS-SRF and ME-SRF respectively. Swelling and water retention capacity of the SRFs in distilled water, NaCl, CaCl2, and FeCl3 solutions were evaluated. The water retention ratio at 4 days was similar 14.76% for both BAS-SRF and ME-SRF in soil and 4.67% for soil without the SRFs. The swelling ratio of the SRFs in solution, followed the order Water > NaCl > CaCl2>FeCl3. The swelling kinetics fitted with Scott's second order swelling kinetic model. The fertilizer release of the standard urea (un-capsulated) in distilled water revealed a cumulative release of about 97% within an hour. Whereas the formulated BAS-SRF and ME-SRF (encapsulated) had a cumulative release of 76% and 68% at 24 h and 96 h respectively. Interestingly, a sustained cumulative urea release was observed in soil; about 95% and 92% at 36 days for BAS-SRF and ME-SRF respectively.

Versatile surface modification of millimeter‐scale “aqueous pearls” with nanoparticles via self‐polymerization of dopamine

The millimeter‐scale calcium alginate aqueous core capsules (mm‐CaSA‐Caps), which own high entrapment efficiency and excellent biocompatibility, have broad applications in food additives and drug delivery. However, due to pH sensitivity and thermal instability of Ca‐alginate, many chemical modifications with intense conditions are hardly conducted on the mm‐CaSA‐Caps. In this work, layer‐by‐layer assembly coating on the surface of the mm‐CaSA‐Caps was proceeded with in situ self‐polymerization of dopamine (DA) and nanoparticles under mild conditions. The colorless and transparent mm‐CaSA‐Caps became beautiful dark “pearls” of polydopamine (PDA) modified mm‐CaSA‐Caps (mm‐PDA@CaSA‐Caps), which had uniform coating of PDA. Obviously, deposition of PDA on mm‐CaSA‐Caps accelerated with higher concentration of DA, weak alkali condition of pH = 8.5, and oxidant of sodium periodate. Water retention ratio of mm‐PDA@CaSA‐Caps also increased because of the PDA coating. The nanoparticles were easily coated on the mm‐PDA@CaSA‐Caps due to the strong adhesive property of PDA. Two‐dimensional laminar montmorillonites were adhered to mm‐PDA@CaSA‐Caps, which lead to better barrier property of capsules than that of the one‐dimensional linear multiwalled carbon nanotubes modified capsules. It was ascribed to increasing of the path length of water by sheet‐like morphology of montmorillonites. This work provided a versatile path for enhancement of barrier property of millimeter‐scale hydrogel capsules.