Removal of BTEX by using a surfactant – Bio originated composite

MOF@biomass hybrids: Trends on advanced functional materials for adsorption

This contribution aims to demonstrate the scope of new hybrids between biomass and metal-organic frameworks (MOF@biomass) used in the adsorption process of pollutants. After a brief presentation of the use of the main series of MOFs as efficient adsorbents for different types of pollutants, the limitations of these structures related to particle size and hydrodynamic problems during their application are highlighted. Lignocellulosic biomasses are also recognized as an alternative adsorbent, mainly due to their high natural abundance and their low environmental impact during and after their application. The limited capacity of bioadsorbents becomes important in this research. Consequently, the largest amount of information existing in the last ten years on MOF-Biomass functionalization as a hybrid and improvement technology for adsorption processes is compiled, analyzed, compared and contrasted. So far, there is no evidence of works that exploit the concept of functionalization of adsorbents of different nature to give rise to new hybrid materials. Through this review it was found that the hybrids obtained show a higher adsorption capacity (Qe) compared to their precursors, due to the increase of organic functional groups provided by the biomass. Thus, for heavy metals, dyes, Arsenium anions and other organic and pharmaceutical compounds, there are increases in Qe of about 100 mg g^-1. The possibility of the new hybrid being studied for desorption and reuse processes is also raised, resulting in a new line of research that is attractive for the industry from an economic and environmental point of view. The functionalization methods and techniques used in the studies cited in this article are outlined. In conclusion, this research brings a new horizon of study in the field of adsorption and mentions the main future challenges related to new sustainable applications.

Combined effects of textural and surface properties of modified ordered mesoporous carbon (OMC) on BTEX adsorption

In this study, we first investigated the effects of textural parameters and surface properties of ordered mesoporous carbon (OMC) for the adsorptive removal of Benzene, Toluene, Ethylbenzene, and Xylene (BTEX) from aqueous solutions. The BET surface area, pore volume, and surface functional groups of OMC played a crucial role in affecting the adsorption performance of BTEX. Boric acid was used to increase the pore size and BET surface area of OMC from 5.94 nm to 6.74 nm and from 1276 m²/g to 1428 m²/g, respectively. Citric acid was used to introduce more oxygen-containing functional groups on the surface of OMC achieving an overall increase of 11.4% of the oxygen content. The batch adsorption experiments were conducted to evaluate the adsorption capacity for OMC and modified towards BTEX and the results showed that modified OMC exhibited a significant improvement for BTEX removal in the following order: Xylenes > Ethylbenzene > Toluene > Benzene. The BTEX adsorption capacities were improved from 8% to 15% with the addition of boric acid compared to the virgin. Surface functionalized using citric acid exhibited the total adsorption capacity of 142 mg/g with an increment of 40.5% compared to virgin OMC.

Development of hybrid processes for the removal of volatile organic compounds, plasticizer, and pharmaceutically active compound using sewage sludge, waste scrap tires, and wood chips as sorbents and microbial immobilization matrices

This study evaluated the reutilization of waste materials (scrap tires, sewage sludge, and wood chips) to remove volatile organic compounds (VOCs) benzene/toluene/ethylbenzene/xylenes/trichloroethylene/cis-1,2-dichloroethylene (BTEX/TCE/cis-DCE), plasticizer di(2-ethylhexyl) phthalate (DEHP), and pharmaceutically active compound carbamazepine from artificially contaminated water. Different hybrid removal processes were developed: (1) 300 mg/L BTEX + 20 mg/L TCE + 10 mg/L cis-DCE + tires + Pseudomonas sp.; (2) 250 mg/L toluene + sewage sludge biochar + Pseudomonas sp.; (3) 100 mg/L DEHP + tires + Acinetobacter sp.; and (4) 20 mg/L carbamazepine + wood chips + Phanerochaete chrysosporium. For the hybrid process (1), the removal of xylenes, TCE, and cis-DCE was enhanced, resulted from the contribution of both physical adsorption and biological immobilization removal. The hybrid process (2) was also superior for the removal of DEHP and required a shorter time (2 days) for the bioremoval. For the process (3), the biochar promoted the microbial immobilization on its surface and substantially enhanced/speed up the bioremoval of toluene. The fungal immobilization on wood chips in the hybrid process (4) also improved the carbamazepine removal considerably (removal efficiencies of 61.3 ± 0.6%) compared to the suspended system without wood chips (removal efficiencies of 34.4 ± 1.8%). These hybrid processes would not only be promising for the bioremediation of environmentally concerned contaminants but also reutilize waste materials as sorbents without any further treatment.

Influence of dissolved organic matter and oil on the biosorption of BTEX by macroalgae in single and multi-solute systems

The effect of dissolved organic matter (DOM) and oil on the removal of the water-soluble compounds benzene, toluene, ethylbenzene, and xylene isomers (BTEX) by two low-cost biosorbents Macrocystis pyrifera and Ulva expansa) was evaluated. DOM decreased the adsorption capacity of toluene, ethylbenzene, and xylenes of the two biosorbents. In contrast, the removal of benzene increased under the same conditions in single and multi-solute systems: this effect was dominant in U. expansa biomass treatments. In the presence of DOM and oil in solutions, the removal of BTEX notoriously increased, being oil that contributed the most. Solubility and hydrophobicity of pollutants played a key role in the adsorption process. The attractions between BTEX molecules and biosorbents were governed by π-π and hydrophobic interactions. Affinities of biosorbents for BTEX were mainly in the order of X > E > T > B. The Langmuir and Sips equations adjusted the adsorption isotherms for BTEX biosorption in deionized and natural water samples, but in the case of oily systems, the Freundlich equation seemed to have a better fit. The biosorption processes followed a pseudo-second-order rate in all the cases.

Reutilization of waste scrap tyre as the immobilization matrix for the enhanced bioremoval of a monoaromatic hydrocarbons, methyl tert-butyl ether, and chlorinated ethenes mixture from water

BTEX (benzene, toluene, ethylbenzene, ortho-, meta-, and para-xylenes), methyl tert-butyl ether (MTBE), cis-1,2-dichloroethylene (cis-DCE), and trichloroethylene (TCE) are among the major soil and groundwater contaminants frequently co-existing, as a result of their widespread uses. Pseudomonas plecoglossicida was immobilized on waste scrap tyre to remove these contaminants mixture from synthetic contaminated water. The microbial activity was enhanced in the immobilized system, shown by the higher colony forming units (CFUs) (40%), while BTEX were used as growth substrates. The adsorption capacity of tyres toward contaminants reached a maximum within one day, with BTEX (76.3%) and TCE (64.3%) showing the highest sorption removal capacities, followed by cis-DCE (30.0%) and MTBE (11.0%). The adsorption data fitted the Freundlich isotherm with a good linear correlation (0.989-0.999) for the initial contaminants concentration range applied (25-125mg/L). The monoaromatic hydrocarbons were almost completely removed in the immobilized system and the favourable removal efficiencies of 78% and 90% were obtained for cis-DCE and TCE, respectively. The hybrid (biological, immobilization/physical, sorption) system was further evaluated with the contaminants spiked intermittently for the stable performance. The addition of mineral salt medium further enhanced the bioremoval of contaminants by stimulating the microbial growth to some extent.

Adsorption of Toluene and Paraxylene from Aqueous Solution Using Pure and Iron Oxide Impregnated Carbon Nanotubes: Kinetics and Isotherms Study

Multiwall carbon nanotubes (CNTs) and iron oxide impregnated carbon nanotubes (CNTs-iron oxide) were investigated for the adsorption of hazardous toluene and paraxylene (p-xylene) from aqueous solution. Pure CNTs were impregnated with iron oxides nanoparticles using wet impregnation technique. Various characterization techniques including thermogravimetric analysis, scanning electron microscopy, elemental dispersion spectroscopy, X-ray diffraction, and nitrogen adsorption analysis were used to study the thermal degradation, surface morphology, purity, and surface area of the materials. Batch adsorption experiments show that iron oxide impregnated CNTs have higher degree of removal of p-xylene (i.e., 90%) compared with toluene (i.e., 70%), for soaking time 2 h, with pollutant initial concentration 100 ppm, at pH 6 and shaking speed of 200 rpm at 25°C. Pseudo-second-order model provides better fitting for the toluene and p-xylene adsorption. Langmuir and Freundlich isotherm models demonstrate good fitting for the adsorption data of toluene and p-xylene.