Renewable biowaste-derived carbon dots have garnered immense interest owing to their exceptional optical, fluorescence, chemical, and environmentally friendly attributes, which have been exploited for the detection of metals, non-metals, and organics in the environment. In the present study, water-soluble fluorescent carbon dots (CDs) were synthesized via facile green microwave pyrolysis of pine-cone biomass as precursors, without any chemical additives. The synthesized fluorescent pine-cone carbon dots (PC-CDs) were spherical in shape with a bimodal particle-size distribution (average diameters of 15.2 nm and 42.1 nm) and a broad absorption band of between 280 and 350 nm, attributed to a π-π* and n-π* transition. The synthesized PC-CDs exhibited the highest fluorescent (FL) intensity at an excitation wavelength of 360 nm, with maximum emission of 430 nm. The synthesized PC-CDs were an excellent fluorescent probe for the selective detection of Cu²⁺ in aqueous solution, amidst the presence of other metal ions. The FL intensity of PC-CDs was exceptionally quenched in the presence of Cu²⁺ ions, with a low detection limit of 0.005 μg/mL; this was largely ascribed to Cu²⁺ ion binding interactions with the enriched surface functional groups on the PC-CDs. As-synthesized PC-CDs are an excellent, cost effective, and sensitive probe for detecting and monitoring Cu²⁺ metal ions in wastewater.

This research focus endeavour to compare the remediation of tetracycline (TC) through activated carbon (AC), crafted utilizing two distinct chemical activators: zinc chloride (ACZ), and potassium hydroxide (ACK), using pine cone biowaste as an effective carbon precursor, followed by microwave-assisted activation. The impact of TC removal by ACZ and ACK adsorbents was thoroughly examined. The influence of pH, adsorbent mass, adsorption isotherms, kinetics, and inclusive thermodynamics were studied. Our results revealed that the interaction between TC and ACZ or ACK adsorbents aligned well with the model of pseudo-second-order kinetics, whilst the Langmuir model fitted the adsorption isotherm data of ACZ and ACK. The ACZ have a maximum adsorption capacity of 327.87 mg/g compared to that of the ACK (283.29 mg/g). Adsorption of TC was facilitated by the suitable pore volume, abundant microporous, and mesoporous structure of these adsorbents. The ACZ adsorbent is abundant in oxygen-containing functional groups, compared to ACK with minimized reactive sites, in bonding with the TC molecules through hydrogen bonding, for faster removal of TC. Our finding from this work further highlights that the synthesized ACZ from pine cones evidenced significant environmental potentials in the elimination of antibiotics from aqueous solution, to promote clean application perspectives.

In this study, pinecone was converted via two stage pyrolysis to produce low cost activated carbon. Furnace pyrolysis was used in the first step to convert pinecone to carbonized material, followed by microwave pyrolysis of the carbonized material activated with KOH to obtain activated carbon (ACK) materials as a suitable catalyst support. The ACK samples were characterized by their morphology, structural, adsorption and electrochemical properties. The optimized ACK 2.24-16 prepared from the pinecone had a complex three-dimensional (3D)-hierarchical porous structure, with an abundance of micropores and mesopores compared to other ACK samples judging from the high iodine number (1900 mg g⁻¹) and the methylene blue number (4000 mg g⁻¹) capacity. The optimized ACK 2.24-16 had the highest current response and least charge transfer resistance, along with moderate surface area (427 m² g⁻¹) as a promising photocatalyst support. The 3D hierarchical porous ACK significantly assisted catalyst dispersion, and enhanced visible light absorption and fast interfacial charge transfer. This work shows the promising aspect of utilizing pinecone to produce a low-cost photocatalyst support for environmental remediation.