Bio-Based Adsorption as Ecofriendly Method for Wastewater Decontamination: A Review

Intense human activities have for years contributed to the pollution of the environment by many dangerous pollutants such as heavy metals, pesticides, or polycyclic aromatic hydrocarbons. There are many conventional methods used to control pollution, with practical and/or financial drawbacks. Therefore, in recent years, an innovative, easy-to-implement and inexpensive adsorption method has been developed to recover waste and clean up water from micropollutants. Firstly, this article aims to summarize the issues related to water remediation and to understand the advantages and disadvantages of the methods classically used to purify water. In particular, this review aims to provide a recent update of the bio-based adsorbents and their use. Differently from the majority of the reviews related to wastewater treatment, in this article several classes of pollutants are considered. Then, a discussion about the adsorption process and interactions involved is provided. Finally, perspectives are suggested about the future work to be done in this field.

Ultrafine Particles Issued from Gasoline-Fuels and Biofuel Surrogates Combustion: A Comparative Study of the Physicochemical and In Vitro Toxicological Effects

Gasoline emissions contain high levels of pollutants, including particulate matter (PM), which are associated with several health outcomes. Moreover, due to the depletion of fossil fuels, biofuels represent an attractive alternative, particularly second-generation biofuels (B2G) derived from lignocellulosic biomass. Unfortunately, compared to the abundant literature on diesel and gasoline emissions, relatively few studies are devoted to alternative fuels and their health effects. This study aimed to compare the adverse effects of gasoline and B2G emissions on human bronchial epithelial cells. We characterized the emissions generated by propane combustion (CAST1), gasoline Surrogate, and B2G consisting of Surrogate blended with anisole (10%) (S+10A) or ethanol (10%) (S+10E). To study the cellular effects, BEAS-2B cells were cultured at air-liquid interface for seven days and exposed to different emissions. Cell viability, oxidative stress, inflammation, and xenobiotic metabolism were measured. mRNA expression analysis was significantly modified by the Surrogate S+10A and S+10E emissions, especially CYP1A1 and CYP1B1. Inflammation markers, IL-6 and IL-8, were mainly downregulated doubtless due to the PAHs content on PM. Overall, these results demonstrated that ultrafine particles generated from biofuels Surrogates had a toxic effect at least similar to that observed with a gasoline substitute (Surrogate), involving probably different toxicity pathways.

Extraction and quantification of pesticides and metals in palm wines by HS-SPME/GC-MS and ICP-AES/MS

In this study, HS-SPME/GC-MS and ICP-AES/MS methods are presented to extract and quantify pesticides and metals in palm wines. Various parameters affecting the extraction were investigated: SPME fiber, equilibrium and extraction time, extraction temperature, salinity, and stirring, through an experimental design with 45 trials. The developed method allowed to identify 35 pesticides and quantify 29 of them, from different families of pesticides in 32 palm wine samples. Method performance was evaluated in terms of linearity, repeatability, LOD, LOQ, and accuracy. Among the 32 samples analyzed in 3 replicates, 7 pesticides were detected in 10 samples. Dichlorvos was the only pesticide detected at levels above the European maximal limits. Additionally, 10 of the 19 metals explored by ICP-AES and ICP-MS were found in all samples. Six metals were detected in different samples at levels above the European or OIV maximal limits for drinking water or wine.

Functional activated carbon: from synthesis to groundwater fluoride removal

Developing green and functional adsorbents for the removal of inorganic pollutants from industrial wastewater is still a great challenge. Activated carbons (ACs) are promising eco-friendly materials for adsorption applications. This study reports on the preparation and functionalization of AC and its application for fluoride removal from water. Activated carbon was prepared from date stems, and the material was employed as a support for different modifications such as incorporation of Al(OH)₃, in situ dispersion of aluminum particles (Al⁰) and grafting of 3-(aminopropyl)triethoxysilane (APTES). The resulting functional adsorbents were fully characterized by Fourier transform infrared spectroscopy, scanning electronic microscopy, energy dispersive X-ray fluorescence, X-ray diffraction, differential scanning calorimetry and zeta potential analysis. The results evidenced successful surface modifications. All adsorbents had affinity for the removal of fluoride ions (F⁻). The highest F⁻ removal rate was up to 20 mg g⁻¹ for AC-Al(OH)₃. Removal of fluoride ions obeyed Langmuir isotherms and a second-order kinetic model, and reached 99% uptake. The AC-Al(OH)₃ adsorbent was successfully used to treat a groundwater solution contaminated by fluoride ions. These results open an interesting avenue for developing eco-friendly functionalized AC for adsorption applications.

Conversion and surface modification of date stems to obtain a relevant adsorbent to remove fluoride contamination.

Toxicological impact of organic ultrafine particles (UFPs) in human bronchial epithelial BEAS-2B cells at air-liquid interface

Air pollution has significant health effects worldwide, and airborne particles play a significant role in these effects. Ultrafine particles (UFPs) have an aerodynamic diameter of 0.1 μm or less, can penetrate deep into the respiratory tree, and are more toxic due to their large specific surface area, which should adsorb organic compounds. The aim of this study is to show the toxicological effects of UFPs with high organic content at low dose on BEAS-2B cells through at air-liquid interface (ALI) exposure using a Vitrocell® technology and a miniCAST (Combustion Aerosol Standard) generator. In conjunction with this approach, chemical analysis of particles and gas phase was performed to evaluate the presence of polycyclic aromatic hydrocarbons (PAHs). Chemical analyses confirmed the presence of PAHs in UFPs. With this experimental setup, exposure of the BEAS-2B cells induced neither cytotoxicity nor mitochondrial dysfunction. However, an increase of oxidative stress was observed, as assessed through Nrf2, NQO1, HO-1, CuZnSOD, MnSOD, and Catalase gene expression, together with significant induction of genes related to xenobiotic metabolism CYP1A1 and CYP1B1. Negative regulation of inflammatory genes expression (IL-6 and IL-8) was present three hours after the exposition to the UFPs. Taken together, this experimental approach, using repeatable conditions, should help to clarify the mechanisms by which organic UFPs induce toxicological effects.

Chromium Determination in Leather and Other Matrices: A Review

Leather industry plays an essential role in the world's economy; however, it also has a negative environmental impact due to the generation of significant quantities of wastes, some of which are classified as hazardous chemicals. Chrome tanning, the most popular tanning process, employs chromium salts, acids, and some other chemicals. Some dyes can be also a source of chromium. As a result, hexavalent chromium, a known carcinogenic and mutagenic, can be found in leather products and cause allergic dermatitis or trigger other diseases. For this reason, it is important to quantify the total amount of chromium in final leather goods, as well as the oxidation state in which this element is found. This paper aims to summarize chromium contamination due to the leather production processes, and to review the analytical methods that have been used to determine chromium's most abundant species: Cr(III) and Cr(VI) in leather and other matrices (foodstuffs, cosmetic products, environmental, and pharmaceutical samples). The international and European regulations are presented as well as the last academic developments to extract and quantify chromium species. The future outlook of pretreatment and quantification techniques are also discussed in this work, with a special focus on chromium interconversions.

Competitive and non-competitive zinc, copper and lead biosorption from aqueous solutions onto flax fibers

Competitive and non-competitive batch experiments were conducted on flax fibers to study Zn²⁺, Cu²⁺, and Pb²⁺ ions biosorption performance. Biosorption efficiency was dependent on contact time, pH, and biosorbent concentration. The results under competitive conditions were different from those obtained in non-competitive form. A high affinity of lead, with a selectivity sequence in general of Pb > Cu > Zn was observed. The biosorption data fitted very well the Langmuir model for lead in both types of solutions and for zinc and copper in the monometal form. The fit with the Freundlich model was not as successful, except for copper in the ternary system. Regarding zinc under competitive conditions, the sorption process was quite difficult and thus the equilibrium data could not fit well the adsorption models. The maximum adsorption capacities (mmol.kg^-1) were respectively 112, 122 and 71, for Pb, Cu and Zn in the single metal ion solution and 82, 57 and 8 only in the ternary, showing thus a high competition between metal ions when added simultaneously. Overall, lead could still be efficiently removed in spite of the presence of other ions while zinc would be overcome in the presence of lead and copper.