Contamination of water by heavy metals is a major environmental concern due to the potential ecological impact on human health and aquatic ecosystems. In this work, we studied the chemical modification of various fruit peels such as banana (BP), granadilla (GP), and orange ones (OP) in order to obtain novel bio-adsorbents to improve the removal of Zn(II) ions from 50 mg·L⁻¹ synthetic aqueous solutions. For this purpose, sodium hydroxide and calcium acetate were employed to modify the fruit peels. The moisture, extractives, lignin, hemicellulose, and cellulose contents of the raw materials were determined according to ASTM standards. The obtained bio-adsorbents were characterized by scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and thermogravimetric analysis (TGA). The results showed the OP bio-adsorbents performed better, especially when the concentration of the modifier solutions increased, e.g., the OP particles modified using 0.8 M NaOH and Ca(CH₃COO)₂ solutions resulted in 97% removal of Zn(II) contaminating ions and reached a maximum adsorption capacity of 27.5 mg Zn per gram of bio-adsorbent. The adsorption processes were found to follow a pseudo-second order model. The error function sum of square error indicated the Freundlich isotherm (non-linear regression) as best fit model. The obtained results are particularly interesting for material selection in wastewater treatment technologies based on contaminant adsorption.

Lead ion in drinking water is one of the most dangerous metals. It affects several systems, such as the nervous, gastrointestinal, reproductive, renal, and cardiovascular systems. Adsorption process is used as a technology that can solve this problem through suitable composites. The adsorption of lead (Pb(II)) on graphene oxide (GO) and on two goethite (α-FeOOH)/reduced graphene oxide (rGO) composites (composite 1: 0.10 g GO: 22.22 g α-FeOOH and composite 2: 0.10 g GO: 5.56 g α-FeOOH), in aqueous medium, was studied. The GO was synthesized from a commercial pencil lead. Composites 1 and 2 were prepared from GO and ferrous sulfate. The GO and both composites were characterized by using scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), Raman spectroscopy, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and dynamic light scattering (DLS). The adsorption capacity of Pb(II) on the GO and both composites was evaluated through adsorption isotherms. Composite 1 presented a significant agglomeration of α-FeOOH nanorods on the reduced graphene oxide layers. Meanwhile, composite 2 exhibited a more uniform distribution of nanorods. The adsorption of Pb(II) on the three adsorbents fits the Langmuir isotherm, with an adsorption capacity of 277.78 mg/g for composite 2200 mg/g for GO and 138.89 mg/g for composite 1. Composite 2 emerged as a highly efficient alternative to purify water contaminated with Pb(II).

The aim of this research was to evaluate the coagulating/flocculating characteristics of three natural polymers: green plantain peel starch, orange peel pectin and tamarind seed extracts in three solutions (water, sodium chloride and ammonium acetate), for the purification of raw natural water with turbidity of 5,32 NTU. Natural polymers did not present coagulant activity due to the low turbidity of raw natural water. However, they showed flocculant activity in combination with aluminum sulfate. The optimal combinations of aluminum sulfate [mg/L] + natural polymer [mg/L] were: 50+0,2 for starch, 60+0,06 for pectin, 60+0,6 for tamarind extract in water, 60+0,5 for tamarind extract in sodium chloride and 60+0,2 for tamarind extract in ammonium acetate. Removal values of turbidity and color were about 87% and 92%, respectively. Residual sludge exceeded the maximum permissible limits for discharging to the sewer system. In addition, it showed a toxic effect on the mitotic activity of onion roots with an IC50 of 0,5 to 2%.

Although cemeteries are sacred sites where decomposing bodies are permanently deposited, until now relatively little attention has been paid to the possibility that they constitute a source of water contamination. The present research intends to evaluate the levels of physicochemical contamination of rivers near ten cemeteries in central Ecuador by analyzing a variety of physicochemical parameters in the field and laboratory during dry and rainy periods. A statistical analysis was conducted, demonstrating that the majority of variables are lacking for regular patterns or homoscedasticity to be demonstrated. Subsequently, an analysis was performed using the Kruskal–Wallis test, concluding that there was no significant difference between sampling sections and periods, but there was between pre-established categories, so for that reason it was decided to work only in the dry season and the results were compared with the EPA regulations, depending on the use of water from each river. It was concluded that there is a high probability of environmental contamination in the river by the cemeteries termed “Not suitable” because they registered greater non-compliance with the maximum permissible limits, while cemeteries categorized as “Completely adequate” had a lower probability of contaminating the water. It is suggested that a normative, globally applicable criterion for the optimal location of cemeteries or final disposal sites be established.

Water bodies and aquatic ecosystems are threatened by discharges of industrial waters. Ecotoxicological effects of components occurring in untreated and treated wastewaters are often not considered. The use of a linear, multi-compartmented, non-forced, static system constructed with PET bottles is proposed for the quality assessment of treated waters, to deal with such limitations. Two synthetic waters, one simulating wastewater from the textile industry and the other one simulating wastewater from the cassava starch industry, were prepared and treated by homogeneous Fenton process and heterogeneous photocatalysis, respectively. Untreated and treated synthetic waters and their dilutions were placed into compartments of the non-forced exposure system, in which zebrafish (Danio rerio), the indicator organism, could select the environment of its preference. Basic physical–chemical and chemical parameters of untreated and treated synthetic waters were measured. The preference and avoidance responses allowed verification of whether or not the quality of the water was improved due to the treatment. The results of these assays can be a complement to conventional parameters of water quality.

Revista Tecnología y Ciencias del Agua (TyCA) del Instituto Mexicano de Tecnología del Agua (IMTA)