Surface-functionalized pomelo peel-derived biochar with mercapto-1,2,4-triazloe for selective elimination of toxic Pb (II) in aqueous solutions

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 124.2 mg/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.

N-doped carbon fibers in situ prepared by hydrothermal carbonization of Camellia sinensis branches waste for efficient removal of heavy metal ions

N-doped carbon fibers (NCFs) were in situ prepared by Camellia sinensis branches waste through hydrothermal carbonization with urea/ZnCl2 at 160-280 °C under 0.8-8.9 MPa. The structural characteristics of NCFs were investigated by elemental analysis, SEM, TEM, XRD, XPS, Raman spectra, and BET surface area. The highest N content of NCFs obtained at 280 °C was 8.96%, and the main forms of doped N were pyridinic N, pyrrolic N, and graphitic N. Moreover, NCFs were applied to remove metal ions successfully. The results showed that NCF-240 had the maximum adsorption amounts of 106.52, 125.23, and 153.49 mg/g for Cu2+, Pb2+, and Zn2+, respectively, while NCF-280 had the best removal ability on Cr6+ (145.67 mg/g). Finally, it demonstrated that the adsorption behavior of NCFs was well fitted by the pseudo-second-order kinetic and the Langmuir adsorption isotherm models.

Efficient removal of Cd (II) from aqueous solution by chitosan modified kiwi branch biochar

Production of cost-efficient composite materials from low-cost modified biochar for the removal of Cd (II) from wastewater is much needed to meet the growing needs of industrial wastewater treatments. A novel chitosan-modified kiwi branch biochar (CHKB) was fabricated as low-cost modified biochar for the removal of Cd (II) from aqueous solution. Batch adsorption and characterization experiments indicated that the modification of kiwi biochar (KB) by chitosan remarkably improved its adsorption performance. The results revealed that the adsorption isotherms can be best described by a Langmuir model and that a pseudo-second-order model fits the Cd (II) adsorption kinetics well, which indicates that it is a monolayer process controlled by chemisorption. CHKB exhibited a Langmuir maximum adsorption capacity of Cd (II) (126.58 mg g^-1), whereas that of KB was only 4.26 mg g^-1. The adsorption ability of CHKB was improved by increasing the surface area and an abundance of surface functional groups (-OH, -NH, CO, etc.). The cation exchange, electrostatic interaction, surface complexation, and precipitation were the main mechanisms in the sorption of Cd (II) on CHKB. Excellent adsorption performance, low cost, and environmental-friendliness made CHKB a fantastic adsorbent for the removal of Cd (II) in wastewater.

Porous ZnCl2-Activated Carbon from Shaddock Peel: Methylene Blue Adsorption Behavior

It is of great interest and importance to resource utilization of waste biomass to produce porous carbon for environmental treatments. Pore structure and properties of the obtained carbon mainly relate to carbonization conditions and biomass types. In this work, a series of porous, biomass-activated carbons (AC) were prepared using shaddock peel, with ZnCl₂ as a pore-forming agent. The effect of carbonization temperature and the mass ratio between ZnCl₂ and shaddock peel were thoroughly investigated. The material composition, surface chemical properties, and surface structures of samples were carefully characterized. The specific surface area and adsorption capacity to methylene blue (MB) of adsorbents were changed with the carbonization temperature and the mass ratios between ZnCl₂ and shaddock peel; when the temperature was at 1000 °C and the mass ratio was equal to 2:1, the resulting adsorbent had the largest specific surface area of 2398.74 m²/g and average pore size of 3.04 nm, which showed the highest adsorption capacity to MB to be 869.57 mg/g. The adsorption processes of biomass AC adsorbent matched the pseudo-second-order kinetic model and Langmuir isotherm model. This efficient and environmentally friendly biomass AC adsorbent from shaddock peel, activated by ZnCl₂, is a promising candidate for the treatment of water pollution.