The current work explores the adsorptive efficiency of carbon nanospheres (CNSs) derived from oil palm leaves (OPL) that are a source of biowaste. CNSs were synthesized at 400, 600, 800 and 1000 °C, and those obtained at 1000 °C demonstrated maximum removal efficiency of ~91% for malachite green (MG). Physicochemical and microscopic characteristics were analysed by FESEM, TEM, FTIR, Raman, TGA and XPS studies. The presence of surface oxygen sites and the porosity of CNSs synergistically influenced the speed of removal of MG, brilliant green (BG) and Congo red (CR) dyes. With a minimal adsorbent dosage (1 mg) and minimum contact time (10 min), and under different pH conditions, adsorption was efficient and cost-effective (nearly 99, 91 and 88% for BG, MG and CR, respectively). The maximum adsorption capacities of OPL-based CNSs for BG were 500 and 104.16 mg/g for MG and 25.77 mg/g for CR. Adsorption isotherms (Freundlich, Langmuir and Temkin) and kinetics models (pseudo-first-order, pseudo-second-order and Elovich) for the adsorption processes of all three dyes on the CNSs were explored in detail. BG and CR adsorption the Freundlich isotherm best, while MG showed a best fit to the Temkin model. Adsorption kinetics of all three dyes followed a pseudo-second-order model. A reusability study was conducted to evaluate the effectiveness of CNSs in removing the MG dye and showed ~92% efficiency even after several cycles. Highly efficient CNSs with surface oxygen groups and speedy removal of organic dyes within 10 min by CNSs are highlighted in this paper.
Acid-dyes, typically used in textile productions, could infer poisoning harmful effects on the environment as well as on human health, if not properly treated during their disposal. Henceforth, there is an absolute necessity to achieve new efficient low-cost techniques to remove these dyes from industrial chemical waste. Here, the leaves of oil palm, which are abundant in tropical countries, were used as precursor in the development of carbon nanospheres (adsorbent) to remove hazardous acid Orange-7 (AO-7) dye (C16H11N2NaO4S). The removal efficacy of spherical-shaped nanocarbons was investigated as a function of contact period, by varying their dose (0.5, 1, 1.5, 2 and 2.5 mg), pH (acidic, native and basic), and initial AO-7 concentration (10, 15, 20, 25 and 30 μM). Amazingly, the oil palm leaves–based carbon nanospheres removed acid-dye up to an efficiency of about 99%. Pseudo second-order kinetics governs the adsorption mechanism and the Redlich–Peterson isotherm model fits well to the adsorption results, with regression co-efficient close to unity. This study suggests the importance of natural biowaste-based carbon nanoparticles in sustainable recycling, within the worldwide demanded circular economy.
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