In this study, cadmium biosorption by Myriophyllum heterophyllum Michx. and Potamogeton crispus L. was investigated. Although both species were found to be capable of removing cadmium from water, the performance of P. crispus was the most significant. These species were treated with 0, 4, 8, 16, 32, and 64 mg L(-1) cadmium solutions for 24, 48, 72, and 96 h, respectively. Cadmium uptake of both species was lowest at 4 mg L(-1 )and highest at 64 mg L(-1). Photosynthetic pigments and total phenolic compounds in both species were determined after exposure to various concentrations of cadmium for various times. Depending on the cadmium accumulation in both species, it was shown to decrease the level of chlorophyll a, chlorophyll b, and carotenoids (24 and 96 h). The anthocyanin concentration in P. crispus increased at all cadmium concentrations studied (0, 4, 8, 16, 32, and 64 mg L(-1)), whereas in Myriophyllum heterophyllum it increased at the lower cadmium concentrations (0, 4, and 8 mg L(-1)) but decreased at higher cadmium concentrations (16, 32, and 64 mg L(-1)), for all exposure periods. The total phenolic compound level in both species increased with cadmium concentration during the 24 and 96 h exposure periods.

Graphical abstract Adsorption of hydroxychloroquine (HCQ) onto H 3 PO 4 -activated Cystoseira barbata (Stackhouse) C. Agardh (derived from algal biodiesel industry waste) biochar was investigated via batch experiments and mathematical models. The activated biochar (BC-H) was produced in a single step by using the microwave irradiation method. Thus, it was obtained with a low cost, energy efficiency and by promoting clean production processes. BC-H exhibited a remarkable adsorption efficiency (98.9%) and large surface area (1088.806 m 2 g −1 ) for removal of HCQ. The Langmuir isotherm and the pseudo-second-order kinetic models were the best fit for the equilibrium adsorption and kinetics experiments, and the maximum monolayer adsorption capacity (qmax) was found to be 353.58 µg g −1 . Additionally, the experiments with real wastewater showed that BC-H's ability to adsorb HCQ was not affected by competitive ions in the water. The Taguchi orthogonal array (L16 OA) experimental design was applied for the effective cost optimization analyses of the adsorption process by considering four levels and four controllable factors (initial pH, HCQ concentration, amount of adsorbent and contact time). Scanning electron microscopy, Fourier transform infrared spectroscopy and Brunauer–Emmett–Teller analyses were used for characterizing the adsorbent. The findings showed that BC-H can be used as an effective and low-cost adsorbent in the removal of HCQ from water. Supplementary Information The online version contains supplementary material available at 10.1007/s13369-021-06235-w.

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The common goal of the Water Framework Directive (WFD) published by The European Parliament and European Council and the Regulation on the Management of Surface Water Quality Directive (RMSWQ) published by the Republic of Turkey, Ministry of Forestry and Water Affairs, is to provide all water bodies to achieve a fine ecological status. These directives require the use of relevant biological quality elements and diatoms constitute an important group within these elements. The use of diatom based indices for assessing ecological conditions in inland water systems is increasing day by day. The current study was performed with the aim of determination of the ecological status of the Taşmanlı Pond based on epilithic diatoms, physico-chemical parameters and to estimate pond water quality using diatom indices. For this purpose, epilithic diatom and water samples were collected from 3 stations in the pond in monthly intervals from March 2008 to March 2009. The identifications of the sampled revealed presence of a total of 46 taxa in the sampled stations. Achnanthidium minutissimum (Kützing) Czarnecki, Nitzschia acicularis (Kützing) W. Smith, Navicula cincta (Ehrenberg) Ralfs in Pritchard and Navicula cryptocephala Kützing were the dominant taxa in all stations. According to Regulation on the Management of Surface Water Quality directive, the pond water was classified as III-IV quality class and trophic status changed from mesotrophic to eutrophic. Significant correlation was determined between LTDI (Lake Trophic Diatom Index) and EQR (Ecological Quality Ratio). The values of LTDI and EQR indicate that, pond water has class III (poor, moderately polluted site) water quality.

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