Synthetic wastewaters treatment by electrocoagulation to remove silver nanoparticles produced by different routes

Abstract

Nanoscience is a field that has stood out in recent years. The accurate long-term health and environmental risks associated with these emerging materials are unknown. Therefore, this work investigated how to eliminate silver nanoparticles (AgNPs) from synthetic effluents by electrocoagulation (EC) due to the widespread use of this type of nanoparticle (NP) in industry and its potential inhibition power over microorganisms responsible for biological treatment in effluent treatment plants. Synthesized AgNPs were studied via four different routes by chemical reduction in aqueous solutions to simulate the chemical variations of a hypothetical industrial effluent, and efficiency conditions of the EC treatment were determined. All routes used silver nitrate as the source of silver ions, and two synthesis routes were studied with sodium citrate as a stabilizer. In route I, sodium citrate functioned simultaneously as the reducing agent and stabilizing agent, whereas route II used sodium borohydride as a reducing agent. Route III used D-glucose as the reducing agent and sodium pyrophosphate as the stabilizer; route IV used sodium pyrophosphate as the stabilizing agent and sodium borohydride as the reducing agent. The efficiency of the EC process of the different synthesized solutions was studied. For route I, after 85 minutes of treatment, a significant decrease in the plasmon resonance peak of the sample was observed, which reflects the efficiency in the mass reduction of AgNPs in the solution by 98.6%. In route II, after 12 minutes of EC, the absorbance results reached the detection limit of the measurement instrument, which indicates a minimum reduction of 99.9% of AgNPs in the solution. During the 4 minutes of treatment in route III, the absorbance intensities again reached the detection limit, which indicates a minimum reduction of 99.8%. In route IV, after 10 minutes of treatment, a minimum AgNP reduction of 99.9% was observed. Based on these results, it was possible to verify that the solutions containing citrate considerably increased the necessary times required to eliminate AgNPs from the synthesized effluent, whereas solutions free of this reagent showed better results on floc formation and, therefore, are best for the treatment. The elimination of AgNPs from effluents by EC proved effective for the studied routes.

A comparative study of synthetic and natural coagulants for silver nanoparticles removal from wastewater

“…In another study, electrocoagulation techniques were used to treat silver nanoparticles from synthetic effluent. Four different chemicals were used, and the results included 98% removal with sodium citrate used as reducing and stabilizing agent, 99.9% removal with sodium borohybride as reducing agent, 99.8% with D-glucose and sodium pyrophosphate as stabilizing agent, and 99.9% removal with sodium pyrophosphate as stabilizing and sodium borohybride as reducing agent [25]. Activated sludge biological flocs were also used successfully to remove silver nanoparticles [26].…”

Electrocoagulation Applied for Textile Dye Oxidation Using Iron Slag as Electrodes

“…The electric current applied to the treatments was based on the literature, ranging from 0.3 A to 0.9 A (Ghanbari et al, 2014;Matias et al, 2015). For better electron conductivity in the e uent, 1 g L -1 of NaCl was added to each treatment.…”

“…The wires used were of a 6 mm gauge, stripped 10 cm at one end to wrap the slag and 5 cm at the other end to connect to the power source, being changed at each experiment. The electric current applied in the treatments was based on the literature, ranging from 0.3 A to 0.9 A (Ghanbari et al, 2014;Matias et al, 2015). For better electron conductivity in the e uent, 1 g L -1 of NaCl was added to each treatment.…”

Toxicity of leachates from pilot reactors simulating a landfill with different concentrations of AgNP

“…Studies have shown that silver nanoparticles can kill liver cells and rat brain cells, in addition to cell death, through the binding of the AgNP to the membrane surface, interfering with cellular respiration and permeability (JU-NAM;LEAD, 2008;BYSTRZEJEWSKA-PIOTROWSKA;GOLIMOWSKI;URBAN, 2009;STANLEY, 2014;ROY et al, 2014;BOUR et al, 2015;DWIVEDI et al, 2015;CANESI;CIACCI;BALBI, 2015;MATIAS et al, 2015). The use of these materials generates nano-residues, which can exhibit various behavior such as agglomeration, aggregation and coating of biomolecules, yet unknown, which regulate the properties of their toxicity (LYNCH; WEISS; VALSAMI-JONES, 2014).…”