Synthesis of carbon nanomaterials on impregnated powdered activated carbon for removal of organic compounds from water / Haiyam Mohammed Abdalraheem Alayan

Carbon nanomaterials (CNMs) are known to be superior to many other existing materials in terms of their remarkable properties. Despite of their strong adsorption affinity, they are limited in practical water treatment application for their difficulties involved in dispersion and separation. Moreover, wastewater contamination by toxic organic compounds has become a world-wide environmental concern because of the undesirable effects of these contaminants. Therefore, this research has been undertaken to explore the potential of directly growing CNMs on microscale support such as the powder activated carbon (PAC) to develop a novel CNM hybrid adsorbent for the removal of bisphenol A (BPA) and methylene blue (MB) from water. In this regard, chemical vapor deposition reactor (CVD) was used to synthesize CNMs on nickel impregnated powdered activated carbon from the decomposition of methane and acetylene. The Design of experiment (DOE) based on the response surface methodology (RSM) with the central composite design (CCD) was used to optimize the reaction temperature, reaction time and gases flowrates to obtain the maximum adsorption along with the maximum possible yield for CNM. The results demonstrated that the optimum conditions were different depending on the characteristics of the carbon precursor and the adsorbate under investigation. The optimized growth conditions for methane decomposition were found at 933 ºC, 20 min, and (H2/CH4) of 1.0. The produced CNM-PAC had multi-structures with groove-like features. Meanwhile, dense carbon nanotubes (CNTs) with tubular structures were dominant in the product obtained from the pyrolysis of acetylene at the optimum growth conditions of a reaction temperature of 550 ºC, a reaction time of 37.3 min, and a gas ratio (H2/C2H2) of 1.0. The physiochemical, and morphological properties of CNM-PAC samples at the optimal conditions were investigated using FESEM, TEM, EDX, BET, Raman spectroscopy, TGA, FTIR, and zeta potential. Adsorption studies for BPA and MB were carried out to evaluate the optimum removal conditions, kinetic, and isotherms. RSM-CCD experimental design was used to conduct the optimization studies and to determine the optimal conditions for the removal of BPA and MB by each selected adsorbent individually. The proposed models were optimized with respect to the operating pH, adsorbent mass and contact time as controlling parameters to correlate their effects on the removal efficiency of the pollutants and the adsorption capacity of the adsorbent. The optimization study showed that the maximum adsorption capacity for the removal of BPA and MB onto the CNM-PAC produced from methane was about 182 and 250 mg/g, respectively. The surface properties of CNT-PAC obtained from the pyrolysis of acetylene were modified by oxidative functionalization using two different methods: sonication with KMnO4, and with KMnO4/ H2SO4, however, the best removal of MB was obtained with the as-prepared CNT-PAC sample. The adsorption behaviors showed that the adsorption kinetics and isotherms were in good agreement with the pseudo second-order equation and the Langmuir isotherm model, respectively with a maximum adsorption capacity of about 175 mg/g

Probing the Effect of Gaseous Hydrocarbon Precursors on the Adsorptive Efficiency of Synthesized Carbon-based Nanomaterials

              The present work investigates the effect of the type of carbon precursor on the adsorptive proficiency of as-prepared carbon nanomaterials (CNMs) for the removal of methylene blue dye (MB) from aqueous media. A comparison study was applied to assess the growth of CNMs from the decomposition of methane (CNMY1) and acetylene (CNMY2) using response surface methodology with central composite design (RSM/CCD). The produced nanomaterials were characterized using FESEM, EDX, TEM, BET surface area, Raman, TGA, FTIR, and zeta potential. The as-prepared adsorbent displayed different morphologies and under the experimental conditions, 10 mg of CNMY1 and CNMY2 was responsible for 97.7 % and 96.80% removal of dye. The maximum adsorptive uptake predicted by Langmuir isotherm was about 250 and 174 mg/g for CNMY1 and CNMY2, respectively. The as-synthesized carbon nanomaterial in this study could be explored as a great potential candidate for dye-bearing wastewater treatment

Growth and optimization of carbon nanotubes in powder activated carbon for an efficient removal of methylene blue from aqueous solution

<p>This work demonstrated the synthesis of carbon nanotubes (CNTs) on powder activated carbon (PAC) impregnated with Ni-catalyst through chemical vapour deposition. The optimized effects of reaction temperature, time and feedstock flow rates on CNT growth were examined. Potassium permanganate (KMnO₄) and potassium permanganate in acidic solution (KMnO₄/H₂SO₄) were used to functionalize CNTs samples. A primary screening of methylene blue (MB) adsorption was conducted. The chemical, physical and morphological properties of the adsorbent with the highest removal efficiency were investigated using FESEM, EDX, TEM, BET surface area, RAMAN, TGA, FTIR, and zeta potential. The resulting carbon nanotube-loaded activated carbons possessed abundant pore structure and large surface area. The MB removal by the as-synthesized CNTs was more remarkable than that by the modified samples. Adsorption studies were carried out to evaluate the optimum conditions, kinetics and isotherms for MB adsorption process. The response surface methodology-central composite design (RSM-CCD) was used to optimize the adsorption process parameters, including pH, adsorbent dosage and contact time. The investigation of the adsorption behaviour demonstrated that the adsorption was well fitted with the pseudo-second-order model and Langmuir isotherm with the maximum monolayer adsorption capacity of 174.5 mg/g. Meanwhile, the adsorption of MB onto adsorbent was driven by the electrostatic attraction and π-π interaction. Moreover, the as-obtained CNT-PAC exhibited good reusability after four repeated operations. In view of these empirical findings, the low-cost CNT-PAC has potential for removal of MB from aqueous solution.</p

The formation of hybrid carbon nanomaterial by chemical vapor deposition: an efficient adsorbent for enhanced removal of methylene blue from aqueous solution

In this study, carbon species were grown on the surface of Ni-impregnated powder activated carbon to form a novel hybrid carbon nanomaterial by chemical vapor deposition. The carbon nanomaterial was obtained by the precipitation of the methane elemental carbon atoms on the surface of the Ni catalyst. The physiochemical properties of the hybrid material were characterized to illustrate the successful growth of carbon species on the carbon substrate. The response surface methodology was used for the evaluation of adsorption parameters effect such as pH, adsorbent dose and contact time on the percentage removal of MB dye from aqueous solution. The optimum conditions were found to be pH = 11, adsorbent dose = 15 mg and contact time of 120 min. The material we prepared showed excellent removal efficiency of 96% for initial MB concentration of 50 mg/L. The adsorption of MB was described accurately by the pseudo-second-order model with R2 of 0.998 and qe of 163.93 (mg/g). The adsorption system showed the best agreement with Langmuir model with R2 of 0.989 and maximum adsorption capacity (Qm) of 250 mg/g

Artificial intelligence models for methylene blue removal using functionalized carbon nanotubes

Abstract This study aims to assess the practicality of utilizing artificial intelligence (AI) to replicate the adsorption capability of functionalized carbon nanotubes (CNTs) in the context of methylene blue (MB) removal. The process of generating the carbon nanotubes involved the pyrolysis of acetylene under conditions that were determined to be optimal. These conditions included a reaction temperature of 550 °C, a reaction time of 37.3 min, and a gas ratio (H2/C2H2) of 1.0. The experimental data pertaining to MB adsorption on CNTs was found to be extremely well-suited to the Pseudo-second-order model, as evidenced by an R2 value of 0.998, an X2 value of 5.75, a qe value of 163.93 (mg/g), and a K2 value of 6.34 × 10–4 (g/mg min).The MB adsorption system exhibited the best agreement with the Langmuir model, yielding an R2 of 0.989, RL value of 0.031, qm value of 250.0 mg/g. The results of AI modelling demonstrated a remarkable performance using a recurrent neural network, achieving with the highest correlation coefficient of R2 = 0.9471. Additionally, the feed-forward neural network yielded a correlation coefficient of R2 = 0.9658. The modeling results hold promise for accurately predicting the adsorption capacity of CNTs, which can potentially enhance their efficiency in removing methylene blue from wastewater

Modification of Poly(vinylidene fluoride-co-hexafluoropropylene) Membranes with DES-Functionalized Carbon Nanospheres for Removal of Methyl Orange by Membrane Distillation

Chemical pollutants, such as methyl orange (MO), constitute the main ingredients in the textile industry wastewater, and specifically, the dyeing process. The use of such chemicals leads to huge quantities of unfixed dyes to make their way to the water effluent and consequently escalates the water pollution problem. This work investigates the incorporation of hydrophobic carbon nanospheres (CNS) prepared from the pyrolysis of acetylene using the chemical vapor deposition technique with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) in order to enhance its hydrophobicity. Moreover, a deep eutectic solvent (DES) was used to enhance the membrane’s porosity. The former was based on the quaternary ammonium salt (N,N-diethyl-ethanol-ammonium chloride) as a chemical addition throughout the membrane synthesis. Direct contact membrane distillation (DCMD) was employed to assess the performance of the modified membrane for treatment of MO contaminated water. The phase inversion method was used to embed various contents of CNS (i.e., 1.0, 3.0, and 5.0 wt.%) with 22:78 wt.% of PVDF-co-HFP/N-Methyl-2-pyrrolidone solution to prepare flat-sheet membranes. The membrane embedded with 5 wt.% CNS resulted in an increase in membrane hydrophobicity and presented considerable enhancement in DCMD permeation from 12 to 35 L/h.m2 with salt rejection >99.9%. Moreover, the composite membrane showed excellent anti-biofouling and mechanical characteristics as compared to the pristine counterpart. Using this membrane, a complete rejection of MO was achieved due to the synergistic contribution of the dye negative charge and the size exclusion effect

Optimization of the Synthesis of Superhydrophobic Carbon Nanomaterials by Chemical Vapor Deposition

Demand is increasing for superhydrophobic materials in many applications, such as membrane distillation, separation and special coating technologies. In this study, we report a chemical vapor deposition (CVD) process to fabricate superhydrophobic carbon nanomaterials (CNM) on nickel (Ni)-doped powder activated carbon (PAC). The reaction temperature, reaction time and H2/C2H2 gas ratio were optimized to achieve the optimum contact angle (CA) and carbon yield (CY). For the highest CY (380%) and CA (177°), the optimal reaction temperatures were 702 °C and 687 °C, respectively. However, both the reaction time (40 min) and gas ratio (1.0) were found to have similar effects on CY and CA. Based on the Field emission scanning electron microscopy and transmission electron microscopy images, the CNM could be categorized into two main groups: A) carbon spheres (CS) free carbon nanofibers (CNFs) and b) CS mixed with CNFs, which were formed at 650 and 750 °C, respectively. Raman spectroscopy and thermogravimetric analysis also support this finding. The hydrophobicity of the CNM, expressed by the CA, follows the trend of CS-mixed CNFs (CA: 177°) CSfree CNFs (CA: 167°) PAC/Ni (CA: 65°). This paves the way for future applications of synthesized CNM to fabricate water-repellent industrial-grade technologies