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The purpose of this paper is to review the novel application of surface plasmon resonance (SPR) in sensing heavy metal ions and the development of SPR to become an alternative heavy metal ions sensor.

The possible dangerous toxic effects of heavy metal ions are revealed in the short introduction. The existing conventional methods for sensing heavy metal ions and their drawbacks are also discussed. To overcome these drawbacks, SPR has been investigated from the basic principle to the potential alternative in sensing heavy metal ions.

Application of SPR in sensing heavy metal ions emerged a decade ago. A wide range of active layers or recognition elements (e.g. polymer, protein, nanoparticles) have been developed to combine with SPR. The detection limit, sensitivity and selectivity of SPR sensing in heavy metal ions have been improved from time to time, until the present.

This paper provides up-to-date and systematic information on SPR sensing for heavy metal ions. Different advancements on active layers or recognition molecules have been discussed in detail and arranged in the order of their chronological evolution. The present review may provide researchers with valuable information regarding novel heavy metal ions sensor using SPR and encourage them to take this area for further research and development.

Preparation of chelating resin to be used in the removal of heavy metal ions from solutions.

Chelating resin based on poly (glycidyl‐methacrylate‐co‐N, N‐methylene‐bis‐acrylamide) containing ethylenediamine was synthesised and used in removal of heavy metals from solutions.

The optimal pH values for adsorption of different metal ions occur in the range 4.0‐10.0 depending on the metal ion used. The adsorption of metal ions increases with increasing treatment duration to reach to the equilibrium state. Also, the adsorption of metal ions depends on the degree of cross linking of the chelating resin, and a higher degree of cross linking results in a lower degree of metal ion adsorption. The chelating resin was highly effective for the collection of metal ions by batch and column methods. The metal ions adsorbed could be eluted with 2M HNO₃ except Co²⁺ and the resin could be reused.

The different factors affecting the metal ions (Cu²⁺, Co²⁺, Cd²⁺, Zn²⁺, Pb²⁺ and Hg²⁺) loading in resin such as pH, contact time and cross linking density were studied.

The practical applicability of the chelating resin for final stage of waste water treatment is recommended for use as a polishing agent.

The resins prepared were used successfully in removing heavy metals from water.

This paper aims to investigation of processes for Pb²⁺ elimination from water/wastewater as a significant public health issue in many parts of world. The removal of Pb²⁺ ions by various nanocomposites has been explained from water/wastewaters. ZnO-based nanocomposites, as eco-friendly nanoparticles with unique physicochemical properties, have received increased attention to remove Pb²⁺ ions from water/wastewaters.

In this review, different ZnO-based nanocomposites were reviewed for their application in the removal of Pb²⁺ ions from the aqueous solution, typically for wastewater treatment using methodology, such as adsorption. This review focused on the ZnO-based nanocomposites for removing Pb²⁺ ions from water and wastewaters systems.

The ZnO-based nanocomposite was prepared by different methods, such as electrospinning, hydrothermal/alkali hydrothermal, direct precipitation and polymerization. Depending on the preparation method, various types of ZnO-based nanocomposites like ZnO-metal (Cu/ZnO, ZnO/ZnS, ZnO/Fe), ZnO-nonmetal (PVA/ZnO, Talc/ZnO) and ZnO-metal/nonmetal (ZnO/Na-Y zeolite) were obtained with different morphologies. The effects of operational parameters and adsorption mechanisms were discussed in the review.

The findings may be greatly useful in the application of the ZnO-based nanocomposite in the fields of organic and inorganic pollutants adsorption.

The present study is novel, because it investigated the morphological and structural properties of the synthesized ZnO-based nanocomposite using different methods and studied the capability of green-synthesized ZnO-based nanocomposite to remove Pb²⁺ ions as water contaminants.

The current review can be used for the development of environmental pollution control measures.

This paper reviews the rapidly developing field of nanocomposite technology.

This information will be useful in the selection of materials and technology for the detection and removal of mercury ions at a low cost and with high sensitivity and selectivity. The purpose of this study is to provide the useful information for selection of materials and technology to detect and remove the mercury ions from water with high sensitivity and selectivity. The purpose of this study is to provide the useful information for selection of materials and technology to detect and remove the mercury ions from water with high sensitivity and selectivity.

Different nano- and bio-materials allowed for the development of a variety of biosensors – colorimetric, chemiluminescent, electrochemical, whole-cell and aptasensors – are described. The materials used for their development also make it possible to use them in removing heavy metals, which are toxic contaminants, from environmental water samples.

This review focuses on different technologies, tools and materials for mercury (heavy metals) detection and remediation to environmental samples.

This review gives up-to-date and systemic information on modern nanotechnology methods for heavy metal detection. Different recognition molecules and nanomaterials have been discussed for remediation to water samples. The present review may provide valuable information to researchers regarding novel mercury ions detection sensors and encourage them for further research/development.

The purpose of this paper is to provide an investigation on a new kind of adsorbent materials, namely, the Prussian blue analog (PBA)-loaded albite-base porous ceramic foam, which can effectively adsorb the heavy metal ion in the wastewater.

The natural zeolite powder has been used as the primary raw material to make a sort of porous ceramic foam by impregnating polymer foam in slurry and then sintering. Adjusting the technological parameters could control the bulk density of the ceramic product, which could float on water with the bulk density less than 1 g/cm³ and also sink in water with the bulk density higher than 1 g/cm³. After desilicating the porous ceramic foam, an Al-Fe type PBA with a strong function of ion exchange was loaded on the ceramic surface by directly yielding.

The adsorption performance for harmful metal ions was greatly improved by combining together the high adsorption capability of the PB analog and the efficient high specific surface area of the porous ceramic foam.

This work presents a PBA-loaded albite-base porous ceramic foam that can effectively adsorb the harmful substance in water, and the adsorption efficiency for some typical harmful ions, i.e., Cd²⁺, Cs⁺ and As(V), was examined under different conditions of the experimental period, the pH value and the ion concentration in the tested solution.

The purpose of this paper is to focus on the removal of copper(II) ions from aqueous model salt solution by using chitosan-coated magnetite nanoparticles.

The chitosan-coated magnetite nanoparticles were characterized using X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric differential thermal analysis. The adsorption of Cu(II) by using magnetite nanoparticles as an adsorbent was investigated under different adsorption conditions. The parameters studied were contact time, adsorbent dose and initial concentrations.

The sorption capacities of prepared samples were studied for the removal of Cu²⁺ ions from aqueous model solutions with varying experimental conditions of the initial metal concentration, contact time and dosage. It is found that the removal percent of Cu²⁺ ions increases with an increase in initial metal concentration, contact time and amount of dosage.

Based on the obtained results, this study recommends that chitosan-coated magnetite nanoparticles can also be applied for removal of some heavy metal ions and/or organic compounds in aqueous solution. It is recommended that this study be shared with the polymer-based nanomaterial researchers, especially material science.

The aim of this study is to examine the effect of carbonization on the surface and its influence on heavy metal removal by water hyacinth based carbon.

Dried water hyacinth stem was used as precursor to prepare carbon based adsorbent by pyrolysis method. The adsorbent proximate (ash, volatile matter and fixed carbon) and elemental (carbon hydrogen nitrogen sulfur) composition, surface area, pore size distribution, surface chemistry was examined and compared.

The results demonstrated that through carbonization in comparison to dried water hyacinth stem, it increased the surface area (from 58.46 to 328.9 m²/g), pore volume (from 0.01 to 0.07 cc/g), pore size (from 1.44 to 7.557 Å) thus enhancing heavy metal adsorption. The metal adsorption capacity of Cd, Pb and Zn was measured and analyzed through induced coupled plasma-mass spectrometer. At metal concentration of 0.1 mg/l adsorption rate for Cd, Pb and Zn was 99% due to increased large surface area, coupled with large pore size and volume. Furthermore, the adsorbent surface hydroxyl group (OH⁻) enhanced adsorption of positively charged metal ions through electrostatic forces.

It is presumed that not only adsorption with synthetic wastewater but real wastewater samples should be examined to ascertain the viability of adsorbent for commercial application.

There are little or scanty data on the effects of carbonization on water hyacinth stem based carbon and subsequent effects on heavy metal removal in effluents.

This paper aims to investigate the reusability of metal/metal oxide-coupled ZnO nanorods (ZnO NRs) to degrade rhodamine B (RhB).

ZnO NRs particles were synthesized by precipitation method and used to remove various types of metal ions such as Cu²⁺, Ag⁺, Mn²⁺, Ni²⁺, Pb²⁺, Cd²⁺ and Cr²⁺ ions under UV illumination. The metal/metal oxide-coupled ZnO NRs were characterized by scanning electron microscope, X-ray diffraction and UV-Vis diffuse reflectance. The photodegradation of RhB dye by these metal/metal oxide-coupled ZnO NRs under UV exposure was assessed.

The metal/metal oxide-coupled ZnO NRs were successfully reused to remove RhB dye in which more than >90% of RhB dye was degraded under UV exposure. Furthermore, the coupling of Ag, CuO, MnO₂, Cd and Ni particles onto the surface of ZnO NRs even enhanced the degradation of dye. The dominant reactive species involved in the degradation of RhB dye were ^•OH- and ^•O₂⁻-free radicals.

The coupling of metal/metal oxide onto the surface of ZnO NRs after metal ions removal could affect the photocatalytic performance of ZnO NRs in the degradation of organic pollutants in subsequent stage.

A good reusability performance of metal/metal oxide-coupled ZnO NRs make ZnO NRs become a desirable photocatalyst material for the treatment of wastewater, which consists of both heavy metal ions and organic dyes.

Metal/metal oxide coupling onto the surface of ZnO NRs particles improved subsequent UV-assisted photocatalytic degradation of RhB dye.

Investigates the fate and toxicity of continuous feeding with increasing dosage of heavy metal ions – Cu, Pb, Zn, Cr(VI) – on biogas production from anaerobic digestion of sewage sludge. The efficiency of the system (as measured by biogas production and volatile organic matter removal rate) was reduced for about 35 days before returning to a steady state with the toxicity ranking Cu > Cr (VI) > Pb >Zn. Also looks at the effect of two “pulse” doses of the metals.

This paper aims to develop an inexpensive, portable, sensitive and environmentally friendly electrochemical sensor to quantify trace metals.

A sensor was constructed by modifying carbon paste electrode for the determination of lead, cadmium and zinc ions using square wave anodic stripping voltammetry (SWASV). The modified electrode was prepared by inserting homogeneous mixture of 2-hydroxy-acetophenonethiosemicarbazone, graphite powder and mineral oil. Various important parameters controlling the performance of the sensor were investigated and optimized. Electrochemical behavior of modified electrode was characterized by cyclic voltammetry.

Modified carbon pastes electrodes showed three distinct peaks at −0.50, −0.76 and −1.02 V vs silver/silver chloride corresponding to the oxidation of lead, cadmium and zinc ions at the electrode surface, respectively. The highest peak currents for all the metal ions under study were observed in the phosphate buffer solution at pH 1 with a deposition time of 70 s. The sensor exhibited linear behavior in the range of 0.25-12.5 μg mL-1 for lead and cadmium and 0.25-10.0 μg mL⁻¹ for zinc. The limit of detection was calculated as 78.81, 96.17 and 91.88 ng mL⁻¹ for Pb2⁺, Cd2⁺and Zn2⁺, respectively. The modified electrode exhibited good stability and repeatability.

A chemically modified electrode with Schiff base was applied to determine the content of cadmium, lead and zinc ions in aqueous solutions using SWASV.