Dehydrate Sewage Sludge as an Efficient Adsorbent for Malachite Green Removal in Textile Wastewater: Experimental and Theoretical Studies

Fabrication of titania/calcium alginate nanocomposite matrix for efficient adsorption and photocatalytic degradation of malachite green

This work aims to examine the two techniques' efficiency for the elimination of malachite green (MG) by photocatalytic degradation and adsorption onto synthesized solid nanomaterials. Three solid samples were prepared as calcium alginate (AG), nanotitania (NT), and nanotitania/calcium alginate composite (TG). The morphological and physicochemical characteristics of the solid nanomaterials were investigated by XRD, TGA, DRS, FTIR, pHPZC, nitrogen adsorption/desorption isotherm, SEM, and TEM. The main experimental conditions were determined for sample dose, shaking time, pH, initial malachite green concentration, temperature, ionic strength, and UV lamp power. The resulting data proved that TG attained the higher adsorption capacity (252.52 mg/g) at 40 °C. The adsorption of MG was well fitted by Langmuir, Temkin, Dubinin-Radushkevich, pseudo-second order, intra-particle diffusion, and Elovich models onto all the prepared samples, confirming the endothermic, spontaneous, and favorable adsorption process. The maximum degradation percent (99.6 %) of MG was achieved by using 1.0 g/L as a catalyst dose, 10 mg/L of initial MG concentration, and 33 W for TG. The photodegradation of MG was well fitted by Eyring-Polanyi and Arrhenius models onto the surface of catalyst. The TG reusability resulted in a decrease in the degradation efficiency by 9.8 %, indicating its great capacity as the first nanotitania/calcium alginate nanocomposite used in removing MG from wastewater by two technologies in the same article.

Malachite green and leucomalachite green in fish: a global systematic review and meta-analysis

Malachite green (MG), an antibiotic with antifungal activity, is illegally used in aquaculture. Given that this chemical is teratogenic and mutagenic, abstinence from intake seems to be a need for public safety. The goal of this systematic review and meta-analysis was to determine the global contamination of fishes by MG and its reduced metabolite, leucomalachite green (LMG), in a number of marine and farmed fish species. For literature published prior to January 2022, several databases (Web of Science, PubMed, and Scopus) were investigated. In total, 20 publications (10 countries, 724 samples) achieved the criteria for inclusion. The overall average MG and LMG concentrations were 0.48 (95% CI: 0.47, 0.49 µg kg^-1) and 0.59 (95% CI: 0.39, 0.79 µg/kg^-1), respectively. Eel (M. albus) 15.50 (95% CI: (14.39, 45.39 µg kg^-1) and eel (A. anguilla) 4.46 (95% CI: 1.23, 7.69 µg kg^-1) had the greatest contamination of MG and LMG, according to the effect size, respectively. Warm-water fish had a concentration of 2.591 (95% CI: 2.25, 2.93 µg kg^-1) while cold-water fish had a concentration of 1.55 (95% CI: 0.25, 2.84 µg kg^-1). Fish containing medium-fat level of 1.86 (95% CI: 1.27, 2.44 µg kg^-1) and high-fat content of 1.10 (95% CI: 0.93, 1.26 µg kg^-1) had accumulate MG and LMG in their tissues, respectively. As a result, total MG observed in countries including China, Iran, and the Netherlands was higher than authorized (2 µg kg^-1). The toxicity of MG and LMG demands more monitoring, especially in countries where these chemicals' residues are significant.