In aqueous systems, heavy metal ions, when present in excess than permissible limits, are dangerous for human beings and aquatic life. Heavy metals cannot be degraded. Rather, they accumulate in living organisms either directly or through the food chain. Inside the body, metal ions can be converted to more toxic forms or can directly interfere with metabolic processes. As a result of metal toxicity, various disorders and damage due to oxidative stress triggered by metal ions have been witnessed. Toxic effects of metallic pollution coupled with the need of pure water for the survival and sanitation have thus prompted researchers to take every possible step to uphold the quality of water. In this regard, various strategies have been developed for the detection and the removal of metal ions from aqueous systems. Here we review metal-free water and methodologies used for rapid detection at low levels. Also, the application of benign materials and methods for metal removal from aqueous systems is detailed. Electrochemical methods, especially stripping and cyclic voltammetry, are commonly used methods for detection, while adsorption and ion exchange methods are quite effective for removal.

Detection and removal of heavy metal ions: a review

Pollution due to heavy metals is currently a serious problems affecting water bodies. The removal of heavy metals is of great concern due to their toxicity at trace levels and accumulation in the biosystem. Here we review the technical feasibility of biosorption and ion exchange methods for the removal of various heavy metals from the aqueous media. Chemical pretreatment of low-cost biosorbents are presented. Chemically modified biosorbents exhibit far better adsorption capacities than unmodified ones. We also highlighted the effect of pH on the biosorption for maximal uptake of heavy metals, because pH modifies the surface charge of the biosorbent as well as the speciation of heavy metals.

Removal of heavy metal ions from aqueous system by ion-exchange and biosorption methods

Water pollution is one of the global challenges that society must address in the 21st century aiming to improve water quality and reduce human and ecosystem health impacts. Industrialization, climate change, and expansion of urban areas produce a variety of water pollutants. In this work, we discuss some of the most recent and relevant findings related to the release of heavy metals, the possible risks for the environment and human health, the materials and technologies available for their removal. Anthropogenic activities are identified as the main source of the increasing amounts of heavy metals found in aquatic environments. Some of the health hazards derived from repeated exposure to traces of heavy metals, including lead, cadmium, mercury, and arsenic, are outlined. We also give some perspectives about several techniques used to detect heavy metals, as well as about the factors that could affect the contaminant removal. The advantages and drawbacks of conventional and non-conventional heavy metal removal methods are critically discussed, given particular attention to those related to adsorption, nanostructured materials and plant-mediated remediation. Some of the commercial products currently used to eliminate heavy metals from water are also listed. Finally, we point out some the requirements and opportunities linked to developing efficient methods for heavy metal removal, such as the ones that exploit nanotechnologies.

Heavy metal water pollution: A fresh look about hazards, novel and conventional remediation methods

Chromium is a potentially toxic and carcinogenic metal originating from natural processes and anthropogenic activities such as the iron steel, electroplating and leather industries. Therefore, chromium should be removed from wastewater to avoid environmental pollution and to recycle chromium in the context of the future circular economy. Here we briefly review aqueous Cr species, their toxicity and methods to remove Cr such as membrane filtration, chemical precipitation, ion exchange, adsorption electrocoagulation, electrochemical reduction, electrodialysis, electrodeionization, photocatalysis and nanotechnology.

Removal of chromium from wastewater by membrane filtration, chemical precipitation, ion exchange, adsorption electrocoagulation, electrochemical reduction, electrodialysis, electrodeionization, photocatalysis and nanotechnology: a review

Rapid industrialization, with economic prosperity set as the prime goal, has always created some secondary intolerable problems such as heavy metal contamination, wastewater that need remediation. Industrial wastewater is the major contributors to contamination of aquatic and terrestrial ecosystems with toxic heavy metals like arsenic, copper, chromium, cadmium, nickel, zinc, lead, and mercury whose hazardous bio-accumulative nature in biotic systems is attributed to their high solubility in the aquatic environments. There has, therefore, always been a need for the removal and/or recovery of these toxic, non-biodegradable, and persistent heavy metals from the industrial wastewater. For several decades, extensive investigations have been performed for easy, efficient, and economic removal of heavy metals with a varying degree of success. Chemical precipitation, adsorption, ion floatation, ion-exchange, coagulation/flocculation and electrochemical methods have been the most readily available conventional methods for the removal of these heavy metals. These methods however have posed some serious shortcomings such as high sludge production needing further treatment, low removal efficiency and high energy requirements. In the present years, newer more efficient, more economic and innovative technologies are being investigated. Recently photocatalysis, electrodialysis, hydrogels, membrane separation technique and introducing newer adsorbents have been developed for better adsorption. Hence in this paper, we have reviewed efforts and technological advances achieved so far in the pursuit of more efficient removal and recovery of heavy metals from industrial wastewaters and have evaluated their efficiency dependence on various parameters such as pH, temperature & initial dosing.

Technological trends in heavy metals removal from industrial wastewater: A review

As a fascinating two-dimensional (2D) layered inorganic ion exchange material, zirconium phosphate (hereafter ZrP) has drawn interdisciplinary attention as an ion exchange material and a competent ...

Revisiting the Old and Golden Inorganic Material, Zirconium Phosphate: Synthesis, Intercalation, Surface Functionalization, and Metal Ion Uptake

Preparation and characterization of 5-sulphosalicylic acid doped tetraethoxysilane composite ion-exchange material by sol-gel method.

Herein, we report the low temperature, template directed synthesis of zirconium resorcinol phosphate (ZrRP) nanocomposite material, within water-in-oil microemulsion with Tergitol-7 as a surfactant. The material was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), simultaneous thermogravimetric analysis (TGA), differential thermal analysis (DTG), energy dispersive X-ray spectrometry (EDX), and specific area electron diffraction (SAED) studies. The powder X-ray diffraction studies revealed that the material is amorphous in nature with hardly developed crystallinity. SEM and TEM micrography studies showed that the ZrRP nanocomposite has nearly spherical morphology with average particle size of 30–40 nm. Viscoelastic behavior of ZrRP gel confirms its non-Newtonian behavior which is indicative of monodisperse nature of ZrRP nanoparticles. ZrRP possesses high ion exchange capacity of 2.9...

Soft Template Assisted Synthesis of Zirconium Resorcinol Phosphate Nanocomposite Material for the Uptake of Heavy-Metal Ions

In this work, a hybrid composite material, acrylamide zirconium(IV) sulphosalicylate (AaZrSs) has been synthesized by intercalating acrylamide into zirconium(IV) sulphosalicylate. The synthetic conditions were varied to optimize the ion exchange properties of the material. The characterization of the material was done using SEM, IR, XRD and TGA so as to identify the various functional groups and ion exchange sites present in the material. The ion exchange capacities of some monovalent and divalent cations were investigated in order to know the working capacity of the composite material. Quantum chemical computations at B3LYP/LanL2DZ level were performed to substantiate the structural conclusions based on instrumental techniques. Investigations into the elution behavior, ion exchange reversibility and distribution capacities of the material towards some heavy metal ions were also performed. The distribution coefficients of certain metal ions were determined in different media and following order is observed; Cd(II) > Pb(II) > Zn(II) > Co(II) > Sn(II). Its selectivity was examined by achieving some important binary separations like Co(II)–Cd(II), Pb(II)–Cd(II), Zn(II)–Cd(II) and Sn(II)–Cd(II). The extent of Cd(II) removal was tested by varying the solution parameters like adsorbent dose, adsorbate concentration, pH of the solution, contact time and temperature. The adsorption process followed second order kinetics and adsorption data was best fitted to Langmuir isotherm with correlation coefficient of 0.994. The values of various thermodynamic parameters like ΔG°, ΔS° and ΔH° were also determined. Hence the composite material can be potentially applied to remove Cd(II) from polluted waters.

Sozia Ahad

Papers

Removal of heavy metal ions from aqueous system by ion-exchange and biosorption methods

Revisiting the Old and Golden Inorganic Material, Zirconium Phosphate: Synthesis, Intercalation, Surface Functionalization, and Metal Ion Uptake

Preparation and characterization of 5-sulphosalicylic acid doped tetraethoxysilane composite ion-exchange material by sol-gel method.

Soft Template Assisted Synthesis of Zirconium Resorcinol Phosphate Nanocomposite Material for the Uptake of Heavy-Metal Ions

Exploring the ion exchange and separation capabilities of thermally stable acrylamide zirconium(iv) sulphosalicylate (AaZrSs) composite material