In this study, we investigated the production conditions of Quercus coccifera hydrochar, which is an inexpensive and easy available adsorbent, for the adsorption of Basic Red 18 (BR18) azo dye. The hydrochar was produced in the eco-friendly subcritical water medium (SWM). The effects of the pH (2–10), adsorbent size (45–106 μm), adsorbent dose (0.5–1.5 g/L), dye concentration (40–455 mg/L), and contact time (5–120 min) were studied via optimization experiments. The optimum conditions were pH 10, particle size of 45 μm, particle amount of 1.5 g/L, dye concentration of 455 mg/L, and 60 min. The removal efficiency increased sharply for the first 5 min; after that the removal efficiency reached a steady state at 60 min, with a maximum removal of 88.7%. The kinetic studies for the adsorption of BR18 dye in aqueous solution using hydrochar showed pseudo-second-order kinetics. The Langmuir and Freundlich isotherm models were used to explain the relationship between adsorbent and adsorbate, and Freundlich isotherm was the most suitable model because of its high regression coefficient (R2) value. The intraparticle diffusion model was used to determine the adsorption mechanism of BR18 onto Q. coccifera acorn hydrochar. Desorption studies were also carried out using different types of acid and different molarities.
In this study, the adsorption capacity of toxic and recalcitrant organic pollutant(s) Remazol Brilliant Blue R (RBBR) onto the invader Xanthium İtalicum (XI) plant was assessed using the Response Surface Method (RSM). The adsorp-tion behavior of RBBR was determined by the spectrophotometric method, FTIR and SEM analysis were used to characterize XI, Brunauer, the Emmett and Teller (BET) analysis was accomplished to find the surface area of the ad-sorbent. The experiment procedures were planned by the Central Composite Design (CCD) whereby a model was built to examine the effects of the different parameters and the possible interaction between them. The correlation factor (R2) for the developed model was 0.985, suggesting that the model could achieve 98.5% of RBBR removal through an adsorption process. The desirability of 0.992 can be attained using the identified optimum conditions: XI = 3g, pH = 9, Time = 84min, RBBR = 50ppm. Under these conditions, the adsorption capacity reached 1.59 mg.g-1, and the removal percentage reached 95%. Freundlich isotherm had the best-fitted values with R2 of 0.999. Furthermore, the adsorption of RBBR onto XI was found to be pseudo-second-order kinetic with R2=0.999. Also, the recovery of RBBR from XI was studied through desorption experiments in presents of 0.5M NaOH. The recovery percentage after 120 min reached 47%. The maximum recovery percentage reached 73% at 24h.
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