Vermiculite bio-barriers for Cu and Zn remediation: an eco-friendly approach for freshwater and sediments protection

Abstract

The increase in heavy metal contamination in freshwater systems causes serious environmental problems in most industrialized countries, and the effort to find ecofriendly techniques for reducing water and sediment contamination is fundamental for environmental protection. Permeable barriers made of natural clays can be used as low-cost and eco-friendly materials for adsorbing heavy metals from water solution and thus reducing the sediment contamination. This study discusses the application of permeable barriers made of vermiculite clay for heavy metals remediation at the interface between water and sediments and investigates the possibility to increase their efficiency by loading the vermiculite surface with a microbial biofilm of Pseudomonas putida, which is well known to be a heavy metal accumulator. Some batch assays were performed to verify the uptake capacity of two systems and their adsorption kinetics, and the results indicated that the vermiculite bio-barrier system had a higher removal capacity than the vermiculite barrier (?34.4 and 22.8 % for Cu and Zn, respectively). Moreover, the presence of P. putida biofilm strongly contributed to fasten the kinetics of metals adsorption onto vermiculite sheets. In open-system conditions, the presence of a vermiculite barrier at the interface between water and sediment could reduce the sediment contamination up to 20 and 23 % for Cu and Zn, respectively, highlighting the efficiency of these eco-friendly materials for environmental applications. Nevertheless, the contribution of microbial biofilm in open-system setup should be optimized, and some important considerations about biofilm attachment in a continuous-flow system have been discussed.

Comparison of Rhodotorula sp. and Bacillus megaterium in the removal of cadmium ions from liquid effluents

“…After 48 h of contact time at 150 rpm and 25°C, the final pH of the samples was measured. The variations of initial values of pH depending on the final values were plotted and the point at which pH variation was not observed corresponded to pH pzc [23,24].…”

“…This analysis gives information about the possible electrostatic interactions between biosorbents and chemical species of metal. The pH pzc was determined using the pH drift method which was tested as indicated by several authors [23,24]. The results obtained are presented in Figure 7.…”

“…Based on the results obtained, it can be concluded that the surface of the studied biosorbents is negatively charged (pH pzc for Rhodotorula sp. is 4.8 and for B. megaterium is 0.9) and during the biosorption process, the biosorbent surface attracted the metal ions with positive charges [23,31].…”

Wicherhamomyces anomalus biofilm supported on wood husk for chromium wastewater treatment

“…The attachment of microbial cells to a solid surface is the first and most important stage of the biofilm formation [47,48]. A good control of the interactions between microbial cells and their support within the biofilm system is of extreme importance to assure its long-term stability [18].…”

Permeable Biosorbent Barrier for Wastewater Remediation

“…This is generally influenced by the type of pollutants to be removed and by the hydro-geological conditions of the site (Vignola et al 2011). Zeolites or clays may be used in permeable barriers as low-cost and eco-friendly materials for adsorbing heavy metals from groundwater (Park et al 2002;Ferronato et al 2016). Clays are natural scavengers of contaminants by taking up ions either through ion exchange or adsorption or both.…”