As an environmentally friendly and low-cost adsorbent, biochar has great potential in wastewater treatment. This study investigated biochar derived from Platanus orientalis L. leaves (PLB) activated by KOH in terms of its capacity and reusability to adsorb p-nitrophenol (PNP). PLB had a large specific surface area and total pore volume, and exhibits good PNP removal with a maximal adsorption capacity of 622.73 mg g⁻¹ at 298 K. Batch experiments showed that PLB had a high PNP adsorption capacity under acidic conditions. Experimental results were well described by the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model. The thermodynamic study showed that PNP adsorption was a spontaneously exothermic process, and increasing temperature was not conducive to adsorption. In addition, PNP adsorption was mainly attributed to hydrophobic interaction. The regeneration experiment showed that PLB had good reusability. After the fifth regeneration, the adsorption capacity of PLB still reached 557.05 mg g⁻¹. The deactivation of oxygen-containing functional groups and pore blockage were the causes for the decrease in adsorption capacity of the recycled PLB. Moreover, the biochar showed good adsorption efficiency and reusability, thereby suggesting its potential to serve as an efficient PNP adsorbent for wastewater treatment.

Porous carbon are excellent electrode materials for energy-storage devices. Here, we present a facile in-situ reduction method to improve the electrochemical performance of carbon materials by gold nanoparticles. The prepared porous carbon microspheres decorated with gold-nanoparticle had a 3D honeycomb-like structure with a high specific surface area of about 1635 m² g⁻¹, confirmed by scanning electron microscopy, transmission electron microscopy, and the Brunauer-Emmett-Teller method. The electrochemical performance of as-synthesized porous carbon microspheres was exemplified as electrode materials for supercapacitor with a high specific capacitance of 440 F g⁻¹ at a current density of 0.5 A g⁻¹, and excellent cycling stability with a capacitance retention of 100% after 2000 cycles at 10 A g⁻¹ in 6 M KOH electrolyte. Our method opened a new direction for the gold-nanoparticle-decorated synthesis of porous carbon microspheres and could be further applied to synthesize porous carbon microspheres with various nanoparticle decorations for numerous applications as energy storage devices, enhanced absorption materials, and catalytical sites.

An electrochemical sensor based on carbon quantum dots (CQDs) and zeolitic imidazolate framework-8 (ZIF-8) composite was fabricated to detect lead(II). The CQDs (2.47 ± 0.52 nm) were synthesized from platanus acerifoli leaves by carbonization and the hydrothermal method. Under the optimal conditions, the fabricated electrochemical sensor had excellent performance in detecting Pb²⁺. The linear range for Pb²⁺ was 1 nM–1 μM, and the limit of detection (LOD) was 0.04 nM and the limit of quantification (LOQ) was 0.14 nM. Moreover, when the solution contained Pb²⁺ and Cd²⁺, the linear range for Pb²⁺ was 50 nM to 1 μM and the LOD was 0.02 nM. When the solution contained Pb²⁺ and Cu²⁺, the linear range for Pb²⁺ was 50 nM–750 nM and LOD was 0.07 nM. Furthermore, even if the solution contained Pb²⁺, Cd²⁺ and Cu²⁺, the linear range for Pb²⁺ was 50 nM–1 μM and the LOD was 0.04 nM. The X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometer (FTIR) and Brunauer-Emmet-Teller (BET) results indicated that the composite electrode materials had abundant oxygen-containing functional groups, a large specific surface area and pore structure, which are conducive to the adsorption of heavy metal ions and improve the detection performance.