Nadia Morin-Crini

Adsorption isotherm models for dye removal by cationized starch-based material in a single component system: Error analysis

This article describes the adsorption of an anionic dye, namely C.I. Acid Blue 25 (AB 25), from aqueous solutions onto a cationized starch-based adsorbent. Temperature was varied to investigate its effect on the adsorption capacity. Equilibrium adsorption isotherms were measured for the single component system and the experimental data were analyzed by using Langmuir, Freundlich, Tempkin, Generalized, Redlich-Peterson, and Toth isotherm equations. Five error functions were used to determine the alternative single component parameters by non-linear regression due to the bias in using the correlation coefficient resulting from linearization. The error analysis showed that, compared with other models, the Langmuir model described best the dye adsorption data. Both linear regression method and non-linear error functions provided the best-fit to experimental data with the Langmuir model.

Cationized starch-based material as a new ion-exchanger adsorbent for the removal of C.I. Acid Blue 25 from aqueous solutions

This article describes the use of a cationized starch-based material as new ion-exchanger adsorbent for the removal of C.I. Acid Blue 25 (AB 25) from aqueous solutions. Batch adsorption studies concerning the effects of contact time, pH and temperature are presented and discussed. Adsorption experimental data showed that: (i) the process was uniform and rapid: adsorption of dye reached equilibrium in 50 min in the wide pH range of dye solutions; (ii) adsorption kinetics followed the pseudo-second order model; (iii) the Langmuir model yielded a much better fit than the Freundlich model for the dye concentration range under study; (iv) this adsorbent exhibited interesting adsorption capacities: on the basis of the Langmuir analysis, the maximum adsorption capacity was determined to be 322 mg of dye per gram of material at 25 degrees C; (v) the adsorption capacity decreased with increasing temperature; and (vi) the negative value of free energy change indicated the spontaneous nature of adsorption.

Evaluation of the phytotoxicity of polycontaminated industrial effluents using the lettuce plant (Lactuca sativa) as a bioindicator

Industrial wastewater containing heavy metals is generally decontaminated by physicochemical treatment consisting in insolublizing the contaminants and separating the two phases, water and sludge, by a physical process (filtration, settling or flotation). However, chemical precipitation does not usually remove the whole pollution load and the effluent discharged into the environment can be toxic even if it comes up to regulatory standards. To assess the impact of industrial effluent from 4 different surface treatment companies, we performed standardized bioassays using seeds of the lettuce Lactuca sativa. We measured the rate of germination, and the length and mass of the lettuce plantlet. The results were used to compare the overall toxicity of the different effluents: effluents containing copper and nickel had a much higher impact than those containing zinc or aluminum. In addition, germination tests conducted using synthetic solutions confirmed that mixtures of metals have higher toxicity than the sum of their separate constituents. These biological tests are cheap, easy to implement, reproducible and highlight the effects caused by effluent treated with the methods commonly applied in industry today. They could be routinely used to check the impact of industrial discharges, even when they meet regulatory requirements for the individual metals.

Cross-linked cyclodextrin-based material for treatment of metals and organic substances present in industrial discharge waters

Summary In this study, a polymer, prepared by crosslinking cyclodextrin (CD) by means of a polycarboxylic acid, was used for the removal of pollutants from spiked solutions and discharge waters from the surface treatment industry. In spiked solutions containing five metals, sixteen polycyclic aromatic hydrocarbons (PAH) and three alkylphenols (AP), the material exhibited high adsorption capacities: >99% of Co2+, Ni2+ and Zn2+ were removed, between 65 and 82% of the PAHs, as well as 69 to 90% of the APs. Due to the structure of the polymer and its specific characteristics, such as the presence of carboxylic groups and CD cavities, the adsorption mechanism involves four main interactions: ion exchange, electrostatic interactions and precipitation for metal removal, and inclusion complexes for organics removal. In industrial discharge waters, competition effects appeared, especially because of the presence of calcium at high concentrations, which competed with other pollutants for the adsorption sites of the adsorbent.

Towards A Convenient Procedure to Characterize Polycyclic Aromatic Hydrocarbons in Sediments Receiving Industrial Effluents

Using pressurized liquid extraction and GC-MS/MS, Polycyclic Aromatic Hydrocarbons (PAH) levels were determined in pond and river sediments receiving effluents from a Chemicals Installation (CI) and a Surface Treatment Installation (STI), respectively. Maximum values were obtained for the STI site with total PAH concentrations of 3000-4000 ng g-1 compared to 200-2500 ng g-1 for the CI site. Furthermore, in the river (STI), for two PAHs (phenanthrene and acenaphthylene), one sample presented concentrations that exceeded the probable effect concentrations leading to this sediment being classified as toxic. However, PAH levels were higher upstream of the STI discharge water than downstream, indicating sediment PAH accumulation was not exclusively due to this industrial activity. At the CI site, the concentrations found at different points showed that in the pond, PAHs were derived from industrial activities but were rapidly diluted in the water mass. PAH fingerprinting following various guidelines, revealed the prevalence of a pyrolytic origin.

Silica Materials Containing Cyclodextrin for Pollutant Removal

This chapter reviews the use of cyclodextrin-silica hybrid systems and cyclodextrin-functionalized silica used as adsorbents or filters for the removal of inorganic and organic pollutants from aqueous solutions in solid-phase extraction and adsorption-oriented processes. Actually, there is a need to develop efficient processes for the synthesis and application of multifunctional silica-based materials for pollutant removal by adsorption or filtration, and for sample purification and concentration using solid-phase extraction.

Adsorption-Oriented Processes Using Conventional and Non-conventional Adsorbents for Wastewater Treatment

The removal of contaminants from wastewaters is a matter of great interest in the field of water pollution. Amongst the numerous techniques of contaminant removal, adsorption using solid materials (named adsorbents) is a simple, useful and effective process. The adsorbent may be of mineral, organic or biological origin. Activated carbon is the preferred material at industrial scale and is extensively used not only for removing pollutants from wastewater streams but also for adsorbing contaminants from drinking water sources (e.g. rivers, lakes or reservoirs). However, its widespread use is restricted due to high cost. In the last three decades, numerous approaches have been studied for the development of cheaper and more effective adsorbents capable to eliminate pollutants at trace levels. This chapter gives a general overview of liquid-solid adsorption processes using conventional and non-conventional materials for pollutant removal. It outlines some of the principles of adsorption and proposes a classification for the different types of materials. Finally, the chapter discusses different mechanisms involved in the adsorption phenomena.

Fundamentals and Applications of Cyclodextrins

Cyclodextrins are natural oligosaccharides obtained from starch. They were discovered in 1891 by Villiers, and attracted major scientific and industrial interests from the late 1970s. Actually, cyclodextrins are among the most remarkable macrocyclic molecules with major theoretical and practical interest for chemistry and biology. Cyclodextrins belong to the family of cage molecules due to their structure, which is composed of a hydrophobic cavity that can encapsulate other molecules. Indeed, the most characteristic feature of cyclodextrins is their ability to form inclusion complexes with various molecules through host-guest interactions. Cyclodextrins and their derivatives have a wide variety of practical applications including pharmacy, medicine, foods, cosmetics, toiletries, catalysis, chromatography, biotechnology, nanotechnology, and textile production. Cyclodextrins are also the object of numerous fundamental studies. Between 2011 and 2015, 18,430 cyclodextrin-related publications have been published. In this chapter, after a brief description of cyclodextrin basics, we highlight selected works on cyclodextrins published over the last 5 years by various research groups.

Hemp-Based Materials for Metal Removal

With the increasing focus on renewable materials and sustainability issues, the development of non-conventional materials from natural resources and possessing complexing properties is currently an area of extensive research due to their potential applications in biosorption processes for pollutant removal. Among them, the hemp plant, an annual high yielding industrial crop grown for its fibres and seeds, is one of the most promising material for biosorption of metal ions from diluted waste streams. In this chapter, an extensive list of hemp-based biosorbent literature has been compiled and discussed. After a brief description of hemp and its properties and applications, the chapter gives a general overview of liquid-solid biosorption processes for metal removal from aqueous solutions onto hemp-based materials.

Hemp-based adsorbents for sequestration of metals: a review

With the increasing focus on renewable materials and sustainability issues, the development of non-conventional materials from natural resources and possessing complexing properties is currently an area of extensive research due to their potential applications in biosorption processes for pollutant removal. Among them, the hemp plant (Cannabis sativa), an annual high yielding industrial crop grown for its fibres and seeds, is one of the most promising materials for biosorption of metal ions from diluted waste streams. In this review, an extensive list of hemp-based biosorbent literature has been compiled and discussed. After a brief description of hemp and its properties and applications, the review gives a general overview of liquid–solid biosorption processes for metal sequestration from aqueous solutions onto hemp-based materials.