Mesoporous Carbon from Optimized Date Stone Hydrochar by Catalytic Hydrothermal Carbonization Using Response Surface Methodology: Application to Dyes Adsorption

Abstract

Providing efficient and environmental friendly ways to recover lignocellulosic waste remains a challenge around the world. In this study, citric acid-catalyzed hydrothermal carbonization (CHTC) was coupled with pyrolysis to convert date seed (Ds) into adsorbent material. In this regard, a central composite design (CCD) using response surface methodology (RSM) was developed to examine the influence of temperature, reaction time, and catalyst dose on the mass yield (Ym(%)) and carbon retention rate (CRR(%)) in the produced hydrochars. The optimized hydrochar (OHC-Ds) was obtained under optimal conditions (200°C, 120 min, 20 mg) and characterized by a Ym(%) and CRR(%) of 59.71% and 75.84%, respectively. Chemical activation by KOH of OHC-Ds followed by pyrolysis at 600°C resulted in an active material (AOHC-Ds) rich in carbon and characterized by a high specific surface area of 1251.5 m2/g, with the dominance of mesopores, as well as an amorphous structure comparable to graphite shown by X-ray diffraction (XRD) analysis. Adsorption experiments of two dyes on AOHC-Ds showed a high maximum adsorption capacity (Qm) of 657.89 mg g−1 for methylene blue (MB) and 384.61 mg g−1 for methyl orange (MO) compared to other conventional adsorbents. This result is due to the low acidity (pHpzc) of the surface of AOHC-Ds, which equals 6.75, and its surface, which is also rich in oxygenated functional groups such as (-OH), (C=O), and (C-O) shown by FTIR analysis. These results suggest that the coupling of CHTC and KOH activation followed by pyrolysis is an encouraging way to prepare an efficient and inexpensive adsorbent to remove dyes in wastewater.

Recent methods in the production of activated carbon from date palm residues for the adsorption of textile dyes: A review

“…Several studies revealed that some adsorbate-adsorbents systems produced high R 2 values for both Langmuir and Freundlich models, which signified that those adsorption systems can be well-described by two isotherm models (Daoud et al, 2017;El Ouadrhiri et al, 2021). This phenomenon can be explained by the existence of both homogenous and heterogeneous types of surfaces on the adsorbent.…”

“…In the literature, only few publications have employed the HTC method to convert DPR into hydrochar. In a study performed by El Ouadrhiri et al (2021), optimum preparation conditions for date seed-based hydrochar (OHC-DS) were found to be 200 °C, 120 min, and 20 mg of temperature, reaction time, and catalyst dose (citric acid), respectively, which corresponded to hydrochar yield of 59.71% and 75.84% of the carbon retention rate. It was observed that when the temperature and residence time were increased from 160 to 240 °C and from 32 to 120 min, respectively, the yield of OHC-DS decreased accordingly.…”

Preparation of High-Performance Porous Carbon Materials by Citric Acid-Assisted Hydrothermal Carbonization of Bamboo and Their Application in Electrode Materials

“…Demir-Cakan et al and Heidari et al have similar reports. Susanti et al synthesized activated carbon with a higher SSA by adding a little amount of CA during HTC, and El Ouadrhiri et al have a similar report. , However, there are limited reports that used this method to achieve a high SSA and high specific capacitance, and most of their SSA are below 2000 m 2 /g. − To the best of our knowledge, the research on the effect of catalytic HTC on the properties of porous carbon is still very limited . Therefore, to further study the effect of adding additives during HTC on the pore structure and electrochemical properties of porous carbon is very necessary.…”

“…Susanti et al synthesized activated carbon with a higher SSA by adding a little amount of CA during HTC, and El Ouadrhiri et al have a similar report. 46,47 However, there are limited reports that used this method to achieve a high SSA and high specific capacitance, and most of their SSA are below 2000 m 2 /g. 48−50 To the best of our knowledge, the research on the effect of catalytic HTC on the properties of porous carbon is still very limited.…”

N,P-co-doped carbocatalyst from olive pomace obtained by catalytic hydrothermal carbonization for efficient dye degradation via persulfate-based advanced oxidation process

“…Therefore, there is a long-standing interest in making OP a source of valuable materials (Aliakbarian, Casazza, and Perego 2011). The HTC has attracted lot of attention compared to other waste pretreatment techniques, because it generates a product rich in carbon (El Ouadrhiri et al 2021), and contributes to the reduction of gaseous emissions and the elimination of the energy-intensive wet feedstock drying process (Titirici 2015). Inspired by these facts, the aim of the present study is rst to synthesize a porous material functionalized by two heteroatoms, nitrogen, and phosphorus, from olive pomace as a renewable carbon source, using the HTC process catalyzed by a doping precursor, and then to test the e ciency of the doped and co-doped synthesized materials in the degradation of organic pollutants in the presence of persulfate.…”