Statistical analyses on effective removal of cadmium and hexavalent chromium ions by multiwall carbon nanotubes (MWCNTs)

Abstract

In this work, multiwall carbon nanotubes (MWCNTs) developed from cobalt-ferrite catalyst on activated carbon (from castor seed), was used as an adsorbent for the removal of cadmium and hexavalent chromium ions. The effectiveness of the adsorbent for the uptake of Cd(II) and Cr(VI)ions from aqueous solution was investigated in a process batch adsorption study. The developed activated carbon and MWCNTs were characterized by Brunauer-Emmett-Teller (BET) surface area analysis, Fourier Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM) for the determination of surface area, functional group, and surface morphology, respectively. The BET surface area of activated carbon and developed adsorbent from Co-Fe/AC was 230.24 and 372.42 m 2 /g, respectively. The operational parameters evaluated on the adsorption efficiency were solution pH, temperature, adsorbent dosage initial metal ions concentration, and contact time. The adsorption of Cd(II) and Cr(VI) were found to have attained equilibrium positions in 60 min for the concentration range tested, respectively. The four linearized adsorption isotherm models; Langmuir, Freundlich, Temkin and Dubinin Radushkevich (D-R) tested, when compared, revealed that Langmuir isotherm fitted well to the experimental data judging from the higher correlation coefficient values (R 2 ) and lower values of the error functions (chi-square (χ 2 ), the sum of square error (ERRSQ/SSE) and the sum of absolute error (EABS))with monolayer adsorption capacities of 404.858 and 243.902 mg/g for Cd(II) and Cr(VI) ions, respectively. Adsorption kinetic models investigated by pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion showed the conformity of pseudo-second-order model to the process adsorption as informed by the higher values R 2 and Adj, R 2 , maximum log-likelihood and smaller ERRSQ/SSE, χ 2 , Akaike information criterion (AIC), Bayesian information criterion (BIC), and Hannan-Quinn information criterion (HQIC). The intraparticle diffusion model plots indicated that intraparticle diffusion was not the only rate-limiting step. Thermodynamic adsorption parameters (ΔH o and ΔG o , ΔS o ) showed that the adsorption of Cd (II) and Cr (VI) ions was spontaneous, endothermic, and increased in randomness between the adsorbate-adsorbent. The mean adsorption energy (E), the heat of adsorption (ΔH o ), and activation energy (E a ) values, revealed the adsorption mechanism of Cd(II) and Cr(VI) onto MWCNTs as a combination of chemical and physical adsorption but dominated more by chemical adsorption. IntroductionWater is particularly important to the existence of living organisms in the world. However, human activities which include population growth, industrialization increase, and urbanization have caused rapid contamination, compromising the availability of potable water [1]. The release of harmful substances like heavy metals, due to human actions, has posed environmental problems, affecting human health [2,3]. Heavy metals like chromium and cadmium when exceed...

Hybrid Coordination Networks for Removal of Pollutants from Wastewater

“…To predict the best kinetic and isotherm model which describes better the adsorption of cadmium and lead ions onto CaCEPPA and CoCEPPA materials, four error functions were applied: correlation coefficient R 2 ; sum of squares of the errors ERRSQ (Equation (9)); chi-square test χ 2 (Equation (10)); average relative error ARE (Equation (11)) [ 59 , 60 , 61 , 62 ]. …”

Preparation and Characterization of Biochar and Activated Carbon Derived from Cashew Bagasse Waste

“…CBB showed the presence of whitish particles and sticky structures on the biochar surface. This might be due to incomplete combustion during the carbonization process in the muffle furnace [47]. CBB also showed more coarse and compacted characteristics, including few pores and cavities.…”

“…This observed morphology must have been attributed to countless volatile components in the form of organic matter and impurities present in the biochar before activation Organic matter decomposition during carbonization process however, must have led to the escape of several volatile components in the biochar which must have resulted into it having such morphology [48]. .Also the heterogeneous surface nature, and irregular shape of CBB suggests its efficient feasibility in the coagulation of heavy metals and organic pollutants [47].…”

“…However, for CBAC the SEM result was less compacted, having an uneven surface with welldeveloped micropores of different shape and sizes. The developed micropores of different shape and sizes, resulting from the hollow structures must have been an indication of successful activation process of orthophosphoric acid (H3PO4), as a result of the heat treatment which erodes fine particles and open up the pores in the process [47]. In addition, the particle size for CBAC was smaller compared to CBB.…”

Facile preparation of amine -functionalized corn husk derived activated carbon for effective removal of selected heavy metals from battery recycling wastewater

“…With the rapid advancement of material science, newer adsorbents with high adsorption capacity, cost effectiveness, eco-friendliness, and selectivity are being reported ( Hashem et al., 2021 ). Several research works have reported the use of different materials beginning with chitosan ( Zarghami et al., 2016 ), clay ( Obayomi and Auta, 2019 ), silica ( Radi et al., 2019 ) zeolites ( Cheng et al., 2021 ), carbon nanotubes ( Khan et al., 2021 ), multiwall carbon nanotubes ( Obayomi et al., 2020 ), metal organic framework ( Ahmadijokani et al., 2021 ), and covalent organic framework ( Xiao et al., 2021 ) amongst others to be utilized as an adsorbent for the treatment of heavy metal pollutants in wastewater. Low sorption and desorption efficiency, unstable chemically at low pH, low selectivity and cost effectiveness are the challenges associated with the aforementioned adsorbents ( Obayomi et al., 2022b ).…”