Promoting sustainability in the mussel industry: mussel shell recycling to fight fluoride pollution

Journal of Cleaner Production, 131 (2016) 485–490

http://dx.doi.org/10.1016/j.jclepro.2016.04.154

Taking into account a background situation where some industrial activities greatly influence fluoride pollution, while other industries generate by-products that could be effective as fluoride bio-sorbents, and bearing in mind sustainability and environmental concern, batch-type experiments were performed to study fluoride sorption/desorption on individual (un-amended) and mussel shell-amended soils and materials. Specifically, the research focused on a forest soil, a vineyard soil, pyritic material, granitic material, and ground mussel shell, as well as on both soils and the pyritic and granitic materials amended with mussel shell. The main findings of the research indicate that the shell amendment clearly increased fluoride sorption in the pyritic material (reaching more than 90%), showing no effect as regards fluoride desorption from this material. The amendment caused a slight increase in fluoride sorption on forest soil, as well as a slight decrease in fluoride desorption from it. The un-amended vineyard soil and the un-amended granitic material had lower fluoride-retention capacity than the forest soil and pyritic material, and it did not change after amending with mussel shell. The mussel shell by itself showed the lowest fluoride-retention potential among the tested materials. As a conclusion, and focusing on applicability, these results can be useful to program the correct use of mussel shell amendment on soils and even on degraded environments with the aim of increasing fluoride retention or removal, thus decreasing risk of environmental pollution due to excessive fluoride concentrations in solid and/or liquid media, also facilitating recycling, sustainability and cleaner production in the mussel shell industry.

Adsorption, desorption and fractionation of As (V) on untreated and mussel shell-treated granitic material

Solid Earth, 6 (1) 337-346 (2015)

doi:10.5194/se-6-337-2015

As(V) adsorption and desorption were studied on granitic material, coarse and fine mussel shell and granitic material amended with 12 and 24 t ha−1 fine shell, investigating the effect of different As(V) concentrations and different pH as well as the fractions where the adsorbed As(V) was retained. As(V) adsorption was higher on fine than on coarse shell. Mussel shell amendment increased As(V) adsorption on granitic material. Adsorption data corresponding to the unamended and shell-amended granitic material were satisfactory fitted to the Langmuir and Freundlich models. Desorption was always <19% when the highest As(V) concentration (100 mg L−1) was added. Regarding the effect of pH, the granitic material showed its highest adsorption (66%) at pH <6, and it was lower as pH increased. Fine shell presented notable adsorption in the whole pH range between 6 and 12, with a maximum of 83%. The shell-amended granitic material showed high As(V) adsorption, with a maximum (99%) at pH near 8, but decreased as pH increased. Desorption varying pH was always <26%. In the granitic material, desorption increased progressively when pH increased from 4 to 6, contrary to what happened to mussel shell. Regarding the fractionation of the adsorbed As(V), most of it was in the soluble fraction (weakly bound). The granitic material did not show high As(V) retention capacity, which could facilitate As(V) transfer to water courses and to the food chain in case of As(V) compounds being applied on this material; however, the mussel shell amendment increased As(V) retention, making this practice recommendable.