Pomelo Peel Research Articles

Enzymatic preparation and characterization of honey pomelo peel cellulose and its cellulose nanofibers

In this study, cellulose was extracted from honey pomelo peel (HPP) using the compound enzyme method and the cellulose nanofibers (CNFs) were prepared from it. The result of optimization experiment showed that the optimal extraction yield of cellulose was 36.57%. The optimal extraction scheme for cellulose was as follows: fixed pH at 4.8, temperature at 48 ℃, extraction time of 75 min, and supplemental amount of HPP powder, pectinase, hemicellulase and laccase were 10, 0.10, 0.10, 0.20 g, respectively. The cellulose samples extracted and purified from HPP contained 74.73% holocellulose, 64.98% cellulose, 59.74% α-cellulose and 366 polymerization degrees. CNFs were prepared by hydrolyzing the moistened cellulose solution with 15 U/mL cellulase at 50 ℃ for 15 h, with the average diameter and Zeta potential of 68.15 nm and −24.1 mV. The crystallinity and specific surface area of CNFs were 60.12% and 193.87 m2/g, while the hydrostatic contact angle of CNFs increased with the ultrasound time. Thermogravimetric analysis showed that both the purified cellulose and CNFs had better thermal stability. Purified cellulose and CNFs play important roles in various fields such as food, medicine, and industry.

Effect of Particle Size of Rice-Husk Derived Silica on the Pyrolysis of Pomelo Peels

Silica with two different sizes i.e. microsilica (MS) and nanosilica (NS) was used as a catalytic support for vanadium (5-15 wt%) in the pyrolysis of pomelo peels. Besides use of pomelo peels (agricultural residues) as a feedstock for the pyrolysis, to contribute to environmental sustainability, rice husk was used as a silica source for obtaining the silica support. From the result, it was found that non-catalytic pyrolysis of pomelo peels gave a bio-oil yield of 33.3 wt%. The catalytic pyrolysis with vanadium-modified silica decreased the bio-oil yields ranging between 27.2-33.1 wt%. This was due to the occurrence of the second reactions generated from the active sites on the catalysts, which leads to the conversion of bio-oil into gas products. For NS catalyst, increasing the amount of vanadium loading directly decreased the bio-oil yields and increased the gas yield. The variation of product phase distribution was not clearly observed for MS catalyst even with various vanadium loadings. In addition, NS catalyst exhibited higher efficiency in reducing the acid content in the bio-oil, and increasing the phenol content. The distinguished properties of the nanoparticles may be the main reason for these phenomena. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Graphene oxide nanosheets immobilised on honeycomb pore structure of pomelo peel for enhanced removal of methylene blue.

Herein, for the first time, a simple, green, direct immersion immobilisation method is reported for graphene oxide (GO) nanosheets using pomelo peel (PL) as a substrate. A GO/PL porous sponge was successfully prepared and used to remove methylene blue (MB) from dye wastewater. Considering the porosity, hydrophilicity and elasticity of the PL, the PL was placed in a GO aqueous suspension through direct immersion immobilisation. The carboxyl and hydroxyl groups in the peel could effectively capture and immobilise the GO nanosheets. GO was adsorbed into the PL pores and dispersed throughout the PL. Finally, the prepared super-hydrophilic and elastic GO/PL exhibited excellent adsorption performance towards MB in dye wastewater. The adsorption results revealed that the adsorption behaviour was consistent with the Langmuir isotherm and quasi-secondary kinetic models. The maximum equilibrium adsorption capacity of GO/PL towards MB was 124.2mg/g, exceeding the values obtained for most of the previously reported adsorbents. Moreover, after five consecutive adsorption-desorption cycles, GO/PL retained 75% of its initial adsorption capacity. Mechanistic analysis revealed that pore filling, electrostatic attraction, ion exchange and hydrogen bonding interactions are the primary driving forces facilitating MB adsorption.

Copper ion/gallic acid MOFs-laden adhesive pomelo peel sponge effectively treats biofilm-infected skin wounds and improves healing quality

Bacterial infection and scar formation remain primary challenges in wound healing. To address these issues, we developed a decellularized pomelo peel (DPP) functionalized with an adhesive PVA-TSPBA hydrogel and antibacterial gallic acid/copper MOFs. The hybrid wound dressing demonstrates favorable biocompatibility. It does not impede the proliferation of fibroblasts or immune cells and can stimulate fibroblast migration, endothelial angiogenesis, and M2 macrophage polarization. Additionally, the dressing can scavenge reactive oxygen species (ROS) and provide antioxidant effects. Furthermore, DPP + MOF@Gel effectively inhibits the viability of S. aureus and E. coli in vitro and in vivo. The histological observations revealed enhanced granulation tissue formation, re-epithelialization, and angiogenesis in the DPP + MOF@Gel group compared to other groups. The local immune response also shifted from a pro-inflammatory to a pro-regenerative status with DPP + MOF@Gel treatment. The skin incision stitching experiment further exhibits DPP + MOF@Gel could reduce scar formation during wound healing. Taken together, the hybrid DPP + MOF@Gel holds great promise for treating bacteria-infected skin wounds and inhibiting scar formation during wound healing.

Crosslinked fish scale gelatin/alginate dialdehyde functional films incorporated with carbon dots derived from pomelo peel waste for active food packaging

A multifunctional and environmentally friendly composite film was developed by incorporating pomelo peel-derived carbon dots (PCDs) into a fish scale gelatin (FSG)/alginate dialdehyde (ADA) biopolymer matrix. ADA was used to reinforce the physicomechanical properties of the FSG film via Schiff base crosslinking. PCDs with strong antioxidant and antimicrobial activities were synthesized via a hydrothermal method. The effect of various PCDs content on the surface morphological, physicochemical, and functional characteristics of the composite films was investigated. The results showed that the introduction of PCDs into the FSG/ADA matrix effectively reinforced the mechanical performance, enhanced the water vapor and water resistance, increased UV-light blocking, conferred fluorescence properties, and improved the thermal properties of the composite films. Under 3 wt% PCDs content, the FSG/ADA/PCDs-3 % composite film not only presented significant antioxidant capacity with a radical scavenging rate of 91.71 % for DPPH and approximately 100 % for ABTS, but also exhibited excellent antimicrobial ability against bacteria and fungi. Results of a preservation experiment showed that the prepared FSG/ADA/PCDs-3 % film preserved the physiological qualities of strawberries post-harvest and extended their shelf-life to 7 days at room temperature. Overall, the fabricated FSG/ADA/PCDs composite films are promising for use in eco-friendly active food packaging.

The Prediction of Cu(II) Adsorption Capacity of Modified Pomelo Peels Using the PSO-ANN Model.

It is very well known that traditional artificial neural networks (ANNs) are prone to falling into local extremes when optimizing model parameters. Herein, to enhance the prediction performance of Cu(II) adsorption capacity, a particle swarm optimized artificial neural network (PSO-ANN) model was developed. Prior to predicting the Cu(II) adsorption capacity of modified pomelo peels (MPP), experimental data collected by our research group were used to build a consistent database. Then, a PSO-ANN model was established to enhance the model performance by optimizing the ANN's weights and biases. Finally, the performances of the developed ANN and PSO-ANN models were deeply evaluated. The results of this investigation revealed that the proposed hybrid method did increase both the generalization ability and the accuracy of the predicted data of the Cu(II) adsorption capacity of MPPs when compared to the conventional ANN model. This PSO-ANN model thus offers an alternative methodology for optimizing the adsorption capacity prediction of heavy metals using agricultural waste biosorbents.

Characterization of pectin extracted from pomelo peel using pulsed ultrasound assisted extraction and acidic hot water extraction process

In the present study, the characteristic properties namely XRD, FTIR, DSC, TGA and FESEM analyses of pectin extracted from pomelo fruit peel using pulsed ultrasound assisted extracted (PUUAE) were compared with those of pectin obtained with the conventional acidic hot water extraction (AHWE) process. The pectin extracted from PUUAE process has been analysed to possess better properties in comparison with the pectin obtained from the AHWE process. Pectin obtained from these two methods had been of high methoxyl pectin with almost similar structure. XRD analysis confirmed that AHWE based pectin possessed lower crystallinity than the PUUAE based pectin. The XRD spectra of PUUAE pectin affirmed sharper and stronger peaks than those of the AHWE based pectin and especially at 18.33° and 29.04° Further, the FTIR study revealed stronger absorption areas for PUUAE based pectin than those pertinent in the AHWE based pectin. This inferred that the pectin extracted with PUUAE had higher degree of esterification than that obtained with the AHWE process. Moreover, the DSC and TGA analyses indicated that PUUAE pectin had higher thermal stability in comparison to AHWE based pectin. The exothermic transition for the PUUAE based pectin was found to occur at higher temperature (245.7 °C) in comparison to the AHWE based pectin sample (239 °C). The TGA study conveyed double-stage decomposition for the PUUAE pectin sample (two DTGA peak temperatures (first at 230 °C and the second at 317 °C)) in comparison to the data obtained for the AHWE based pectin sample (a single peak only appears at 182 °C). The FESEM study affirmed a smoother surface with more structural integrity for PUUAE based pectin than that pertinent in the AHWE pectin sample. Therefore, the obtained characteristics can be inferred to the view that the PUUAE process is effective for the production of high quality pectin from pomelo peel (PP) for relevant functional applications.

Comparative Study for Citrus Fruits Phytochemical Screening and In-vitro Antioxidant Activity

Oxidative stress is one of pharmacological & toxicology mechanisms as an important pathological mechanism proposed for many diseases including cancer . Plant components that include antioxidant components are becoming more popular as an alternative to synthetic antioxidants because of their ability to eliminate free-radical intermediates and prevent further oxidation, Citrus genus, which belongs to the Rutaceae family, comprises among of the world's most frequently harvested crops due to its many nutritional and health advantages.
 The preliminary phytochemical analysis of the prepared extract shown the presence of several constituents of citrus peels as Alkaloids, Phenolics , Flavonoids and rutin. Moreover , The result of in-vitro antioxidants activity of both citrus species showed that DPPH radical scavenging activity for peel extract demonstrate dose-dependent inhibition with IC50 was calculated (287.32 ug/ml and 341.89 µg/ml) for pomelo & orange respectively compared to IC50 value of vitamin C which was 260.06 µg/ml as standard antioxidant . in conclusion , study results showed that pomelo peel show higher antioxidant activity compared to orange moreover, citrus peel has significant antioxidant qualities and is a potentially rich source of natural antioxidants, and PPE scavenges DPPH and reactive oxygen radicals very effectively.

Efficient removal of purine compounds from solutions via biomass carbons derived from pomelo peel

The high purine diet could result in the increase of the level of blood uric acid, causing serious health problems such as hyperuricemia, gout, nephropathy and cardiovascular diseases. To find out a safe, cheap and super adsorption material for removing purines in stomach or pretreating high-purine beverages, we used different tissues of pomelo peel to prepare biomass carbon by drying, chemical modification and carbonization and then applied it to remove purine compounds in strong acidic solution, beer and soybean milk. The characteristic analysis of pomelo-peel-derived carbons (PPCs) indicated that the preparation methods significantly affected the structures and adsorption capacities of PPCs. Compared with the biomass carbon derived from bamboo, PPCs exhibited higher adsorption capabilities for purine compounds in strong acidic solution (adsorption rates > 99% in 15min) and soybean milk (adsorption rates > 56% in 30min) but slightly lower adsorption capabilities in beer (adsorption rates > 52% in 30min). In addition, the adsorption capabilities of PPCs for purine compounds in beer and soybean milk were not obviously affected by temperatures. Therefore, PPCs are promising absorbents for applications in removing purine compounds from beverages to produce low-purine, healthier products for treating hyperuricemia. The strong adsorption capabilities of PPCs on purine compounds in strong acidic environment also provides a possibility of using the PPCs as food additives for removing purines in stomach for healthcare applications such as gout prevention after confirming their biosafety.

Pyrolysis Enzymolysis-Treated Pomelo Peel: Porous Carbon Materials with Fe-Nx Sites for High-Performance Supercapacitor and Efficient Oxygen Reduction Applications.

This paper proposes a different strategy for deriving carbon materials from biomass, abandoning traditional strong corrosive activators and using a top-down approach with a mild green enzyme targeted to degrade the pectin matrix in the inner layer of pomelo peel cotton wool, inducing a large number of nanopores on its surface. Meanwhile, the additional hydrophilic groups produced via an enzymatic treatment can be used to effectively anchor the metallic iron atoms and prepare porous carbon with uniformly dispersed Fe-Nx structures, in this case optimizing sample PPE-FeNPC-900's specific surface area by up to 1435 m2 g-1. PPE-FeNPC-900 is used as the electrode material in a 6 M KOH electrolyte; it manifests a decent specific capacitance of 400 F g-1. The assembled symmetrical supercapacitor exhibits a high energy density of 12.8 Wh kg-1 at a 300 W kg-1 power density and excellent cycle stability. As a catalyst, it also exhibits a half-wave potential of 0.850 V (vs. RHE) and a diffusion-limited current of 5.79 mA cm-2 at 0.3 V (vs. RHE). It has a higher electron transfer number and a lower hydrogen peroxide yield compared to commercial Pt/C catalysts. The green, simple, and efficient strategy designed in this study converts abundant, low-cost waste biomass into high-value multifunctional carbon materials, which are critical for achieving multifunctional applications.

Effects of steam explosion on physicochemical, functional and structural properties of soluble dietary fiber from pomelo peel

Abstract The effects of steam explosion (SE) on the physicochemical, functional and structural characteristics of soluble dietary fiber (SDF) extracted from pomelo peel were evaluated. At the treatment condition of 0.9 MPa,120 s, the extraction yield of SDF increased by 156.7 %, and the water holding capacity, oil holding capacity, and swelling capacity increased by 36.6 %, 42.7 %, and 21.4 %, respectively. Additionally, in vitro hypoglycemic capacity, cation exchange capacity, nitrite ion adsorption capacity, and antioxidant capacity were all improved. It was observed that a large number of cracks in the SDF, and the structure of SDF became loose and porous and specific surface area of SDF increased to 1.41 times. In addition, the results from differential scanning calorimetry indicated that SDF treated with SE had better thermal stability, and the degradation temperature increased from 311.93 °C to 316.28 °C. So, SE could be used as an effective method for modifying dietary fiber.

Compressible polydopamine modified pomelo peel powder/poly(ethyleneimine)/κ-carrageenan aerogel with pH-tunable charge for selective removal of anionic and cationic dyes

In this work, a novel biomass-based aerogel, polydopamine decorated pomelo peel powder/polyethyleneimine/κ-carrageenan (PPEKC) aerogel, was developed for dye wastewater treatment. The as-prepared PPEKC aerogel possessed a robust structure and good compressible resilience. As expected, this aerogel presented remarkable efficacy in eliminating both anionic and cationic dyes. The experimental maximum adsorption capacities were 2016.7 mg g−1 for congo red (CR) at pH = 5 and 1176.6 mg g−1 for methylene blue (MEB) at pH = 11, following with ultra-fast adsorption rates. The adsorption kinetics followed the pseudo-second-order model. The adsorption isotherms exhibited a stronger alignment with the Langmuir isotherm model for CR at 308 K and MEB at 288, 298, 308 K. The Freundlich isotherm model yielded a suitable fit for the adsorption of CR at 288 and 298 K. Thermodynamic analyses indicated that the removal of CR and MEB was spontaneous and endothermic. The adsorption mechanisms involved electrostatic interactions, π-π interactions, and hydrogen bonds. Intriguingly, it could achieve bidirectional selective adsorption of anionic and cationic dyes in the designed pH values, due to pH-tunable surface charge. Additionally, it also exhibited favorable reusability and antibacterial activity. Therefore, the as-prepared PPEKC aerogel could be a promising biosorbent for dye wastewater treatment.

Oxalic acid enhanced removal of heavy metal and pesticide by peroxymonosulphate activation with a green biochar iron composite: Reactivity and mechanism

Nowadays, clean-up of heavy metals and pesticides from environment has received great attention. A green biochar iron composite (PC-ZVI) was successfully synthesized using pomelo peel residues and FeCl3 solution. Peroxymonosulfate (PMS) was introduced into the PC-ZVI system for Cr(VI) and atrazine (AE) removal, and results showed that PMS greatly promoted Cr(VI) and AE removal. The presence of oxalic acid (OA) could maintain a relatively high dissolved Fe2+ species for Cr(VI) reduction and AE oxidation in the PC-ZVI/PMS process. The contribution order of reactive oxygen species followed as HO• > SO4•- greater than1O2 > O2•− in both Cr(VI) and AE removal by PC-ZVI/PMS/OA process. A total of six intermediates products of AE degradation were detected, and AE molecular was effectively degraded into CO2, H2O, inorganic N and Cl through hydroxylation, substitution and de-alkylation processes. The underlying mechanism of Cr(VI) and AE removal by PC-ZVI/PMS/OA process was also proposed. Most Cr(VI) species were transformed into Cr2O3 and Cr(OH)3 through reduction and precipitation processes. PC-ZVI has a relatively high recyclability toward both Cr(VI) and AE removal from solutions. The potential toxicity of PC-ZVI solution was small at three PC-ZVI dosages levels, and the corresponding toxicity of AE reaction solution by PC-ZVI/PMS/OA process decreased as reaction time increased. The order of both Cr(VI) and AE removal in different water systems was tap water > river water > lake water > wastewater, and this PC-ZVI/PMS/OA process exhibited the better adaptability in application for several actual water environments.

Film Properties of Pectin Obtained from Various Fruits’ (Lemon, Pomelo, Pitaya) Peels

Food by-products, as sources of high-value compounds, have shown great promise for formulating novel food packaging and edible films for food preservation. This work focused on extracting pectin from lemon, pomelo, and pitaya peels using an ethanol precipitation method. The degree of esterification and the monosaccharide composition of the extracted pectin were determined, and the antioxidant activity of the pectin was assessed. Subsequently, pectin-based films were prepared using the casting method, employing pectin from various sources. These films’ physical and mechanical properties (tensile strength and elongation at break) were assessed, and their microstructure and intermolecular interactions were examined using scanning electron microscopy and Fourier transform infrared spectroscopy analysis. The results of this study demonstrate variations in the degree of esterification among the three pectin samples, with pomelo peel and lemon peel pectins exhibiting higher degrees of methylation compared to pectin from pitaya peel, which had a lower degree of methylation. However, no significant differences were observed regarding the films’ moisture content and water vapor permeability. Notably, the films made from pitaya peel pectin exhibited superior tensile strength and elongation at break to those derived from pomelo peel and lemon peel pectins. The pectin recovered from these fruit peels had great film properties and thus could be utilized for food packaging and edible films.

Pomelo (Citrus maxima. Merr) essential oil extraction by cold pressing and hydrodistillation methods and comparison of chemical composition

Essential oils extraction from the shell bring many applications in life, as well as contribute to the development of the food flavoring and cosmetic industry. Pomelo (Citrus maxima Merr) essential oil (EO) was extracted by cold pressing and hydrodistillation methods. The EO content obtained was 0.067% and 0.33%, respectively. The chemical composition was determined by the GC-MS analysis method, with 4 main components being D-Limonene, β-Myrcene, α-Pinene, and α-Phellandrene which exhibited high antibacterial and antioxidant capacity). The EO obtained from pomelo peels by cold pressing conditions was limited and less effective with more natural aroma, as compared to the hydrodistillation methods. Therefore, further research on EO pressing equipment and methods that can be used for effective oil extraction and recovery are necessary.

Enhancement of anti-diabetic activity of pomelo peel by the fermentation of Aspergillus oryzae CGMCC23295: In vitro and in silico docking studies

In this work, pomelo peel was fermented by Aspergillus oryzae CGMCC23295 to enhance its anti-diabetic properties. Results showed the total phenolic and flavonoids contents, ferric reducing antioxidant power (FRAP), scavenging capacities against 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radicals, as well as inhibitory abilities against α-amylase and α-glucosidase of pomelo peel were increased and fermentation for 8 days was the best. Additionally, the fermented sample could also enhance the glucose consumption and glycogen of HepG2 cell. Based on UPLC-MS/MS analysis, binding energy calculation, concentration determination and IC50 measurement, purpurin, apigenin, genistein, and paxilline could be concluded to be the main compounds to enhance the inhibition activities of fermented sample against α-amylase and α-glucosidase. Furthermore, computational studies were performed to reveal the the binding site and molecular interactions between paxilline and α-amylase, as well as purpurin and α-glucosidase. These findings provide a base for the utilization and valorization of pomelo peels as functional food additives by fermentation.

Mussel-inspired fabrication of pH-responsive pomelo peels as “smart” bio-based adsorbents for controllable removal of both cationic and anionic dyes

In this work, novel and eco-friendly pH-responsive bio-based adsorbents derived from the pomelo peel (PP) were successfully developed. The fabrication process involved the self-polymerization of dopamine to form polydopamine (PDA) on the surfaces of PP, followed by the immobilization of pH-responsive copolymer (P) onto the PDA decorated PP (PDA@PP) using the dip-coating method. The results demonstrated that the as-obtained bio-based adsorbent (PDA@PP-P) with a single dip-coating, denoted as PDA@PP-P-1, exhibited optimal comprehensive properties. Due to the presence of catechol and tertiary amino moieties, the as-prepared PDA@PP-P-1 displayed highly efficient adsorption for both cationic and anionic dyes across a wide pH range from 3 to 10. The adsorption capacity of the PDA@PP-P-1 toward anionic dyes decreased with an increment of solution pH, whereas the opposite trend was observed for cationic dyes. The increment of ionic strength weakened the adsorption performance of as-obtained PDA@PP-P-1 toward dyes except for anionic dyes at high pH, which was slightly influenced. Generally, the adsorption kinetics obeyed the pseudo-second-order kinetic model, while the adsorption isotherm models for dyes’ adsorption were inconsistent. The maximum experimental adsorption amounts were 1750.6 mg g−1 for methyl orange (MO) and 959.2 mg g−1 for congo red (CR) at low pH, 1081.4 mg g−1 for methylene blue (MEB) and 873.4 mg g−1 for crystal violet (CV) at high pH. The electrostatic interactions, π-π interactions and hydrogen bonding were proposed as adsorption mechanisms. Interestingly, as-obtained PDA@PP-P-1 could achieve pH-dependent separation of mixture dyes, due to the significant differences in adsorption capacity and adsorption rate of cationic and anionic dyes under different pH values. Moreover, it exhibited outstanding recyclability under both acidic and alkaline environments. Most importantly, it also presented excellent antibacterial activity against E. coli and S. aureus, followed by antibacterial efficiency of over 99.9 %. Therefore, it could be considered an advanced bio-based adsorbent with enormous potential for dye wastewater remediation.

Exploitation of pomelo peel developing porous biochar by N, P co-doping and KOH activation for efficient CO2 adsorption

In order to improve the exploitation of biochar-based adsorbents for CO2 capture, novel biochar adsorbents were synthesized with pomelo peel by effective two-step carbonization and activation, (NH4)2HPO4 and KOH were taken as the dopant and activator, then a series of N, P co-doped pomelo peel-based biochar (NPBCs) was prepared, subsequently, the characteristics and adsorption capacity of NPBCs were studied. The results showed that N, P co-doping and KOH activation synergistically promoted the development of meso-, micro-, ultra-micropores and nanocapsules structure in NPBCs, and enabled NPBCs maintaining a certain N, P content. The optimum sample of NPBCs reached the highest CO2 adsorption capacities of 3.41 and 5.74 mmol/g at 298.15 K, 273.15 K and 1 bar. The adsorption kinetics and isotherms of CO2 on biochar were perfectly described by PFO model and Sips model respectively, indicating that the adsorption was a rapid process and dominated by physical effect. Measurements of the thermal range of CO2 adsorption (15.59–26.01 kJ/mol) confirmed strong affinity of the NPBCs to CO2 molecules. CO2/N2 selectivity up to 165 was recorded at ambient temperature and low CO2 partial pressure. The loss of adsorption capacity of NPBCs was only 9.36% after 10 cycles showing good cyclic stability.

Enhanced soil P immobilization and microbial biomass P by application of biochar modified with eggshell

Phosphate fertilizers have been excessively applied in agricultural production, bringing the risk of phosphorus (P) loss to nearby river systems and low utilization efficiency. In this study, eggshell-modified biochars prepared by pyrolysis of eggshell and corn straw or pomelo peel were applied to soil for enhancing P immobilization and utilization. The structure and properties of modified biochars before and after P adsorption were analyzed using the Brunauer-Emmett-Teller (BET) nitrogen adsorption method, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). The eggshell-modified biochar performed an excellent adsorption performance for P (up to 200 mg/g), which was well described by the Langmuir model (R2 > 0.969), showing monolayer chemical adsorption with homogenous surface. The Ca(OH)2 appeared on the surface of eggshell modified biochars and changed to Ca5(PO4)3(OH) and CaHPO4(H2O)2 after P adsorption. The release of immobilized P by modified biochar increased with decreased pH. In addition, pot experiments of soybean indicated that the combined application of modified biochar and P fertilizer significantly increased the content of microbial biomass P in soil, raising from 4.18 mg/kg (control group) to 51.6–61.8 mg/kg (treatment group), and plants height increased by 13.8–26.7%. Column leaching experiments showed that P concentration in the leachate decreased by 97.9% with the modified biochar application. This research provides a new perspective that the eggshell-modified biochar could serve as a potential soil amendment for enhancing P immobilization and utilization.

Upgrading pomelo peels into laser-induced graphene for multifunctional sensors

Converting waste pomelo peels into high value-added products is highly desirable both economically and environmentally. Although pomelo peels can be upgraded into carbon materials by direct pyrolysis or hydrolysis, these pyrolysis methods require stringent conditions or cumbersome procedures. In this work, we developed a simple and efficient method based on direct laser writing (DLW) technology to upgrade pomelo peels into high value-added laser-induced graphene (LIG) with a yield of about 30 wt%. The upgraded LIG exhibits good properties such as a porous structure and a high conductivity. Multifunctional sensors were fabricated by coating LIG electrodes with sensing materials for detecting light, humidity, and phosphate. Owing to the good properties of the upgraded LIG, the sensors displayed decent sensing performances. This work offers a potential solution for transforming agricultural waste into high-value-added products in a simple and efficient way.