Green synthesis of Quercus coccifera hydrochar in subcritical water medium and evaluation of its adsorption performance for BR18 dye

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.

Remazol Brilliant Blue R (RBBR) dye and phosphate adsorption by calcium alginate beads modified with polyethyleneimine

“…At that point, adsorption will stop. Langmuir also assumes that there is no migration or interaction between the adsorbate and PEI‐CaAlg beads surface (Saleh et al, 2021). The adsorptions of both RBBR and phosphate onto PEI‐CaAlg beads were found to follow Freundlich isotherm (highest correlation coefficient and lower chi‐square value).…”

“…Desorption studies for the beads at the optimum conditions were done as described previously in the previous works (Saleh et al, 2021). Briefly, the desorption processes were realized at the end of the adsorption process using four acid types (HCl, H 2 SO 4 , HNO 3 , and H 3 PO 4 ) and sodium hydroxide (NaOH) to explore the maximum desorption rate.…”

Green production of hydrochar nut group from waste materials in subcritical water medium and investigation of their adsorption performance for crystal violet

“…Many researchers have used different materials as adsorbents (Yagub et al, 2014). Activated carbon (Agarwal et al, 2016), zeolite (Brião et al, 2018), bio-adsorbent materials from different sources plant (Saleh et al, 2019), fungal materials (Bouras et al, 2019), agricultural wastes (Dai et al, 2018), starchcapped zinc selenide nanoparticles/AC (Sharifpour et al, 2020), Pinus eldarica stalks activated carbon (Jafari et al, 2017), activated carbon with multimodal pore size distribution prepared from Amygdalus scoparia (Bagheri et al, 2019), biochar (Biswas et al, 2020;Qiu et al, 2009), and hydrochar (Abaide et al, 2019;Saleh et al, 2020) are the most prominent materials.…”

“…Hydrochar, a stable solid product rich in carbon, with superior properties to biochar obtained by conventional methods such as classical torrefaction, pyrolysis, or gasification processes, can be produced from many types of biomass (Chuntanapum & Matsumura, 2009;Kumar & Gupta, 2009). The subcritical water medium (SWM) provides a unique medium for carbonaceous materials conversion to hydrochar with a relatively high yield compared to the methods mentioned above (Saleh et al, 2020). The extraction of valuable materials from many different matrices, oxidation of hazardous compounds, synthesis of organic and inorganic compounds, and solubility of poorly soluble materials can be achieved in SWM, thanks to the changeable physico-chemical properties of subcritical water (Yabalak, 2018a(Yabalak, , 2018b.…”

“…There is a growing interest in hydrochar production and its use in various environmental processes and agricultural applications (Fang et al, 2014). It is known that hydrochars have a significant adsorption capacity to remove dye contaminants from water (Saleh et al, 2020).…”