Abstract
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.
Highlights
Water pollution is a global issue (Saleh et al ), and the textile industry is a major source of pollutants as it generates hazardous and colored wastewater that has harmful effects on human life and the environment (Patel & Vashi )
The maximum pore diameter is 17.88 nm, which is larger than the Basic Red 18 (BR18) molecule
The results showed that the maximum removal efficiency was obtained when the particle size was smaller than
Summary
Water pollution is a global issue (Saleh et al ), and the textile industry is a major source of pollutants as it generates hazardous and colored wastewater that has harmful effects on human life and the environment (Patel & Vashi ). Many researchers have tried to treat dyes in wastewater using different methods. Chemical treatment methods have been used: advanced oxidation processes (AOPs) (Al-Kdasi et al ; Miklos et al ), coagulation-flocculation (Verma et al ; Dotto et al ), electrocoagulation (EC) (Naje et al ), electro-Fenton (EF) (Rosales et al ), and anodic oxidation (AO) (dos Santos et al ). The mass transfer concept has been used to remove dyes from wastewater using physical processes. They include the adsorption (Rafatullah et al ), membrane filtration ( Jegatheesan et al ), and ion-exchange methods (Bayramoglu et al ). The low cost, simplicity of design, high efficiency, and easy operation make the adsorption process more favorable than others (Asfaram et al )
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