Evaluation of a low-cost adsorbent for removal of toxic metal ions from wastewater of an electroplating factory

Bifunctional collagen fiber/carbon quantum dot fluorescent adsorbent for efficient adsorption and detection of Pb2

In this work, fluorescent adsorbents that can efficiently detect and remove Pb²⁺ were developed by integrating the designed amino-modified carbon quantum dots and carboxyl-modified collagen. The adsorption properties of the fluorescent adsorbent were further optimized and analyzed using a series of response surface experiments. The maximum adsorption concentration for Pb²⁺ was 183 mg.g^-1. The adsorption isotherms fit well with the Langmuir model, and the adsorption kinetics fit with the pseudo-second-order model. The emission intensity of the fluorescent adsorbent gradually decreased with the increase of the concentration of Pb²⁺, and had a good linear correlation. In addition, the mechanism of detection and removal of Pb²⁺ by fluorescent adsorbents was further demonstrated. The novel three-dimensional structured fluorescent aerogel can be used as a promising adsorbent with good adsorption concentration and sensing ability for Pb²⁺, which shows great prospects in wastewater.

Remediation of Potential Toxic Elements from Wastes and Soils: Analysis and Energy Prospects

The aim of this study is to evaluate the application of the main hazardous waste management techniques in mining operations and in dumping sites being conscious of the inter-linkages and inter-compartment of the contaminated soils and sediments. For this purpose, a systematic review of the literature on the reduction or elimination of different potential toxic elements was carried out, focusing on As, Cd and Hg as main current contaminant agents. Selected techniques are feasible according to several European countries’ directives, especially in Spain. In the case of arsenic, we verified that there exists a main line that is based on the use of iron minerals and its derivatives. It is important to determine its speciation since As (III) is more toxic and mobile than As (V). For cadmium (II), we observed a certain predominance of the use of biotic techniques, compared to a variety of others. Finally, in mercury case, treatments include a phytoremediation technique using Limnocharis flava and the use of a new natural adsorbent: a modified nanobiocomposite hydrogel. The use of biological treatments is increasingly being studied because they are environmentally friendly, efficient and highly viable in both process and energy terms. The study of techniques for the removal of potential toxic elements should be performed with a focus on the simultaneous removal of several metals, since in nature they do not appear in isolation. Moreover, we found that energy analysis constitutes a limiting factor in relation to the feasibility of these techniques.

The environmental impact of informal and home productive arrangement in the jewelry and fashion jewelry chain on sanitary sewer system

The outsourcing informal home practices adopted in jewelry and fashion jewelry chain can cause toxic substance elimination in the effluents and raise a concern for its environmental impact. This study evaluates if this informal work alters the concentration of potentially toxic elements (PTEs: As, Cd, Cr total and Cr-VI, Cu, Hg, Ni, Pb, Sn, and Zn) in the sewage network. The sanitary sewage samples (n = 540) were collected in 15 manholes during two campaigns in three different areas of Limeira-SP, Brazil (industrial area, with informal work and without known industrial/informal activity). The sewage sludge (n = 12), raw (n = 12), and treated sewage (n = 12) were collected in two wastewater treatment plants (WWT: AS and TATU) operating with different treatment process. The PTE determination was performed by ICP-OES, direct mercury analysis, and UV-Vis spectroscopy. Cr-VI, Cu, Ni, and Zn were the only elements above the quantification limit. Four samples exceeded Cu or Zn values permitted to be discharged into sewage system; however, the concentration average was lower than that established by Brazilian legislation. A difference was found between values above and below the 75th percentile for campaign and total organic carbon values (p < 0.015). The AS-treated sewage presented low concentrations of Cu (p < 0.05), Zn (p = 0.02), and Ni (p = 0.01) compared to treated sewage from TATU. In the sludge samples, the Cu means exceeded the limits of the Brazilian legislation (1500 mg kg^-1) and the Zn results were very close to the limits (2800 mg kg^-1). The heterogeneity of the results can indicate the sporadic nature of the PTE's sanitary disposal. PTEs used in jewelry and fashion jewelry chain may precipitate on the sludge, where presented high concentrations of Cu and Zn which require controlled destination.

Dielectric spectroscopy study of water hyacinth collected from different media

X-ray fluorescence (XRF) study has been shown that the water hyacinth plant is an effective tool for the removals of heavy metals (As, Ba, Cr, Cu, Ni, Pb, Rb, Sr, Zn and Zr) and metal oxides (SiO₂, K₂O, CaO, Al₂O₃, Fe₂O₃, MgO, Na₂O, MnO, P₂O₅, SO₃ and TiO₂) from agriculture (media 1) and agriculture wastewaters drainage polluted with municipal wastewater (media 2). As a general description, the heavy metals and metal oxides were found at higher levels in the plant collected from media 1 than those in the plant collected from media 2. Similarly, these pollutants were found at higher levels in the plant roots than those in the plant shoots. The dielectric properties were investigated for the plant samples before (control) and after treating by microwave heating power. They were found at higher values in the control roots than those in the control shoots. Furthermore, the properties were found at relatively higher values in the control roots collected from media 1 (ε'=13 at 10³Hz) than those in the control roots collected from media 2 (ε'=9 at 10³Hz). The electrical conductivity of the microwave treated samples remarkably increased due to appearance of OH group through which the plant interacts with heavy metals. Accordingly, the pollutants removing ability could be enhanced upon treating the plant by microwave heating power. The plant-pollutant mixture behaves like highly conductive disordered polymers. The conductivity and dielectric properties of all plant samples are dominated by the media and concentration of pollutants.

Biosorption of metal ions using a low cost modified adsorbent (Mauritia flexuosa): experimental design and mathematical modeling

Buriti fibers were subjected to an alkaline pre-treatment and tested as an adsorbent to investigate the adsorption of copper, cadmium, lead and nickel in mono- and multi-element aqueous solutions, the results showed an increase in the adsorption capacity compared to the unmodified Buriti fiber. The effects of pH, adsorbent mass, agitation rate and initial metal ions concentration on the efficiency of the adsorption process were studied using a fractional 2(4-1) factorial design, and the results showed that all four parameters influenced metal adsorption differently. Fourier transform infrared spectrometry and X-ray fluorescence analysis were used to identify the groups that participated in the adsorption process and suggest its mechanisms and they indicated the probable mechanisms involved in the adsorption process are mainly ion exchange. Kinetic and thermodynamic equilibrium parameters were determined. The adsorption kinetics were adjusted to the homogeneous diffusion model. The adsorption equilibrium was reached in 30 min for Cu(2+) and Pb(2+), 20 min for Ni(2+) and instantaneously for Cd(2+). The results showed a significant difference was found in the competitiveness for the adsorption sites. A mathematical model was used to simulate the breakthrough curves in multi-element column adsorption considering the influences of external mass transfer and intraparticle diffusion resistance.

Dielectric spectroscopic studies on the water hyacinth plant collected from agriculture drainage

The present paper aims to investigate the sensitivity of dielectric spectroscopy to changes in concentrations of pollutants (heavy metals and metal oxides) uptake by the water hyacinth plant collected from agriculture wastewater drainage. The measurements were carried out on the dried root and shoot plant parts before and after subjecting to different microwave heating powers for different times. Dielectric properties of the untreated root were investigated at temperature range (30-90°C). X-ray fluorescence spectroscopy (XRF) results showed that the concentration of metals and metals oxides are higher in plant root than in plant shoot. Accordingly, the obtained dielectric properties were found to depend on the applied electric field frequency, magnitude of heating power as well as concentrations of pollutants. Analysis of experimental data represented by the imaginary part of the dielectric modulus M″ (ω) revealed to the presence of three different relaxation processes. The lower frequency relaxation process was associated to charge carriers conduction whereas those appeared at higher frequencies were associated to different types of interfacial polarization. The plant ability for removing heavy metals and metal oxides from the aquatic environments would be enhanced upon subjecting to microwave heating power with 400 W for 30 min.

Removal of Cu(II) from acidic electroplating effluent by biochars generated from crop straws

The removal efficiency of copper (Cu(II)) from an actual acidic electroplating effluent by biochars generated from canola, rice, soybean and peanut straws was investigated. The biochars simultaneously removed Cu(II) from the effluent, mainly through the mechanisms of adsorption and precipitation, and neutralized its acidity. The removal efficiency of Cu(II) by the biochars followed the order: peanut straw char > soybean straw char > canola straw char > rice straw char >> a commercial activated carbonaceous material, which is consistent with the alkalinity of the biochars. The pH of the effluent was a key factor determining the removal efficiency of Cu(II) by biochars. Raising the initial pH of the effluent enhanced the removal of Cu(II) from it. The optimum pyrolysis temperature was 400 degrees C for producing biochar from crop straws for acidic wastewater treatment, and the optimum reaction time was 8 hr.

Equilibrium and kinetic studies of cadmium(II) and lead(II) ions biosorption onto Ficus carcia leaves

Background

Ficus carcia leaves (fig leaves) for the removal of cadmium(II) and lead(II) ions from aqueous solutions have been investigated.

Results

The biosorption of cadmium(II) and lead(II) ions was found to be dependent on the solution pH, initial metal ion concentrations, biosorbent dose, contact time, and temperature. The experimental equilibrium biosorption data were analyzed by two widely used two parameters, Langmuir and Freundlich isotherm models.

Conclusions

Langmuir isotherm model provided a better fit with the experimental data than Freundlich model by high correlation coefficients R 2. Kinetic studies showed that pseudo-second-order described the biosorption experimental data better than the pseudo-first-order kinetic model.

Green coconut shells applied as adsorbent for removal of toxic metal ions using fixed-bed column technology

This study applies green coconut shells as adsorbent for the removal of toxic metal ions from aqueous effluents using column adsorption. The results show that a flow rate of 2 mL/min and a bed height of 10 cm are most feasible. Furthermore, larger amounts of effluent can be treated for removal of single ions. The breakthrough curves for multiple elements gave the order of adsorption capacity: Cu(+2) > Pb(+2) > Cd(+2) > Zn(+2) > Ni(+2). Real samples arising from the electroplating industry can be efficiently handled.