Green and sustainable zero-waste conversion of water hyacinth (Eichhornia crassipes) into superior magnetic carbon composite adsorbents and supercapacitor electrodes

Abstract

Troublesome aquatic weed, water hyacinth (Eichhornia crassipes) was converted into solid and liquid fractions via green and energy-saving hydrothermal carbonization (HTC). The solid product, hydrochar, was employed as a precursor to prepare magnetic carbon materials by simple activation and magnetization using KOH and Fe 3+ ions, respectively. The obtained magnetic adsorbent possessed good magnetic properties and presented outstanding capacities to adsorb methylene blue (524.20 mg g À1 ), methyl orange (425.15 mg g À1 ) and tetracycline (294.24 mg g À1 ) with rapid adsorption kinetics even at high concentrations (up to 500 mg L À1 ), attributed to high specific surface area and mesopore porosity.Besides the solid hydrochar, the water-soluble liquid product was used to fabricate carbon-based supercapacitors through facile KOH activation with a considerably lower KOH amount in comparison to conventional activation. The supercapacitor electrode made from activated liquid product possessed an extremely high specific surface area of 2545 cm 2 g À1 and showed excellent specific capacitance (100 F g À1 or 50 F cm À3 at 1 A g À1 ) and good retention of capacitance (92% even after 10 000 cycles). This work demonstrated that both solid and liquid HTC fractions from this bio-waste can serve as effective sources to prepare functional carbon materials, making this approach a sustainable zero-waste biomass conversion process. Scheme 1The preparation steps of magnetic adsorbent (MWHHTC(1)-800) and carbon-based supercapacitor (CLP + KOH-800) using water hyacinth as a carbon precursor.This journal is

Application of Water Hyacinth Biomass (Eichhornia crassipes) as an Adsorbent for Methylene Blue Dye from Aqueous Medium: Kinetic and Isothermal Study

“…This model also predicts that the adsorption process is favorable, as the R 2 linearity value was close to 1 for both the stem and leaf [70]. The Langmuir model was observed in other adsorption studies using water hyacinth biomass [71].…”

Corn Stalk-Based Carbon Microsphere/Reduced Graphene Oxide Composite Hydrogels for High-Performance Symmetric Supercapacitors

“…Even at 10 A g –1 , the specific capacitance of CS/rGO-3 can still remain at 230.4 F g –1 , with an 81.87% retention rate, and the specific capacitance of rGO at the same current density is 116.6 F g –1 , only retaining 80.34%. The outstanding capacitance retention rate of CS/rGO-3 indicates that it has excellent specific capacitance and good rate performance and it can be incriminated to the EDLC characteristics of the materials . More importantly, introducing CSs is obviously beneficial to the hydrophilicity of composite materials, thus leading to robust structural stability, and the oxygen-containing functional groups on their edge can also provide a certain pseudocapacitance.…”

“…The outstanding capacitance retention rate of CS/rGO-3 indicates that it has excellent specific capacitance and good rate performance and it can be incriminated to the EDLC characteristics of the materials. 54 More importantly, introducing CSs is obviously beneficial to the hydrophilicity of composite materials, thus leading to robust structural stability, and the oxygen-containing functional groups on their edge can also provide a certain pseudocapacitance. In addition, the synergistic effect between CSs and graphene sheets can facilitate the charge transfer of the CS/rGO samples.…”

Synthesis of activated carbons from water hyacinth biomass and its application as adsorbents in water pollution control

“…Using activated carbon obtained from lignocellulose biomass instead of fossil coal will reduce the production of greenhouse gasses and therefore represents a green approach in synthesis of materials that can be used in process of pollutant removal 2 . The water hyacinth is characterized by a high content of lignocellulose biomass, including 48 % hemicellulose as the major component, along with 20 % cellulose and with 10 % of average lignin content, so it can be potentially employed as a proper carbon source [3][4][5] .…”