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

Abstract

SummaryIn 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.

Simultaneous removal of Cd, Co, Cu, Mn, Ni, and Zn from synthetic solutions on a hemp‐based felt. II. Chemical modification

“…This coating can be easily observed on SEM images [Figure (d)]. Indeed, our results showed that the COO – groups are responsible for metal ion binding through electrostatic interactions and ion‐exchange, and their presence in Hemp 2A positively influenced its performance. In addition the electrostatic repulsions among the carboxylate anions resulted in the swelling of the polymer network and the increase in the size of the pores, also favoring the metal adsorption.…”

“…Thus, metal ions can easily diffuse inside and outside: the high performance obtained for modified hemp can be explained both the presence of surface adsorption, diffusion, and chemisorption mechanisms. During the curing step at 160 °C of the felt process, two out of the four carboxylic functions of BTCA reacted with both the anhydroglucose units of MALTO and cellulose to form the polymer network, thus the two residual free carboxylic groups remained available to react with cations through chemisorption …”

“…Hemp 1 and Hemp 2A were also characterized by solid‐state C‐NMR technique (the conditions were previously described in detail) and the spectra of the two felts are presented in Figure . The cross‐polarization magic angle spinning (CPMAS) spectrum for Hemp 1 [Figure (a)] shows the peaks of disordered cellulose (broad signals attributable to the glucopyranose unit) in the range of 50–110 ppm which represent the cellulose structure of the raw fiber.…”

“…Besides, our group has recently reported the use of crosslinked cyclodextrin‐based material for treatment of metals and organic substances present in industrial discharge waters. In this work, a resin based on cyclodextrin crosslinked with 1,2,3,4‐butanetetracarboxylic acid (BTCA) presented versatile properties thanks to its chemical composition based on carboxylic acids and cyclodextrins cavities in the polymer network . In this work, the hemp‐based felt mentioned was treated with a mixture of maltodextrin and BTCA in order to ameliorate its adsorption properties toward the same six cationic metal species (Cd, Co, Cu, Mn, Ni, and Zn).…”

Simultaneous removal of Cd, Co, Cu, Mn, Ni, and Zn from synthetic solutions on a hemp‐based felt. III. Real discharge waters

“…An analysis of all the chemical and biological results showed that an additional treatment with hemp represents an interesting tool for decreasing the environmental impact of industrial effluent. Besides both types of hemp materials presented performances in a lesser extent reduction for waters parameters (e.g., nitrites, total P, and HI) and in removal of organic contaminants due an absence of specific interaction between these substances and the materials . This limit could be circumvented in case a cyclodextrin was used in place of maltodextrin.…”