Recycled-tire pyrolytic carbon made functional: A high-arsenite [As(III)] uptake material PyrC350®

High efficiency removal of heavy metals using tire-derived activated carbon vs commercial activated carbon: Insights into the adsorption mechanisms

In this study, activated carbon was derived from pulverized waste tires using carbonization and chemical activation techniques. Single and competitive batch adsorption experiments for the removal of three synthetic heavy metal ions (Pb^2+, Cu²⁺ and Zn²⁺) from an aqueous solution were performed to benchmark the efficiency of the Tire-derived Activated Carbon (TAC) in comparison to that of commercial activated carbon (CAC), which was used as the reference material. The sorbents physicochemical properties with corresponding adsorption mechanisms were evaluated by different experimental techniques. TAC exhibited great potential to adsorb heavy metals, with monolayer adsorption capacities as high as 322.5, 185.2, and 71.9 mg g^-1 for Pb²⁺, Cu²⁺ and Zn²⁺, respectively, which were significantly higher than the adsorption capacities exhibited by CAC, which were 42.5, 15.0, and 14.0 mg∙g^-1 for Pb²⁺, Cu²⁺ and Zn²⁺, respectively. Competitive adsorption results demonstrated the adsorption ability of sorbents is restricted by presence of other ions, and was decreased compared to the single sorption. Sorption kinetics data, with better fit to the pseudo-second order kinetics model, revealed that TAC had faster sorption rate in comparison to CAC. The adsorption capacities of TAC and CAC were reduced to half of their initial capacities after three successive adsorption-desorption cycles. Zeta potential, FT-IR, and XPS analyses revealed that electrostatic attraction and surface complexation mechanisms, as two metal-adsorbing mechanisms, were more influential for TAC. For CAC, a higher cation exchange capacity (CEC) value indicated that the removal of heavy metals by ion exchange was the predominant mechanism.

Assessing the cyto-genotoxic potential of model zinc oxide nanoparticles in the presence of humic-acid-like-polycondensate (HALP) and the leonardite HA (LHA)

The present study investigates the potential cyto-genotoxic effects of model zinc oxide nanoparticles (ZnO NPs) on human lymphocytes, with and/or without humic acids (HAs). Two types of HAs were studied, a natural well-characterized leonardite HA (LHA) and its synthetic-model, a humic-acid-like-polycondensate (HALP). The Cytokinesis Block Micronucleus (CBMN) assay was applied in cell cultures treated with different concentrations of ZnO NPs (0.5, 5, 10, 20 μg mL^-1) and under different concentrations of either HALP or LHA (ZnO NPs-HALP and ZnO NPs-LHA, at concentrations of 0.5-0.8, 5-8, 10-16, 20-32 and 0.5-2, 5-20, 10-40, 20-80 μg mL^-1, respectively). According to the results, ZnO NPs lacked genotoxicity but demonstrated cytotoxic potential. Binary mixtures of ZnO NPs-HAs (ZnO NPs-HALP or ZnO NPs-LHA) showed negligible alterations of micronuclei (MN) formation in challenged cells, with cytotoxic effects revealed only in case of cells treated with ZnO NPs-LHA at the concentration 5-20 μg mL^-1. Furthermore, no genotoxic phenomena were exerted neither by the ZnO NPs nor from their mixtures with HAs. These findings indicate [i] the cytotoxic activity of used ZnO NPs on human lymphocytes, and [ii] reveal the protective role of HAs against ZnO NPs mediated cytotoxicity.

A Hybrid {Silk@Zirconium MOF} Material as Highly Efficient AsIII-sponge

Exposure of humans to Arsenic from groundwater drinking sources is an acute global public health problem, entailing the urgent need for highly efficient/low-cost Arsenite (As^III) up-taking materials. Herein we present an innovative hybrid-material, ZrMOF@SF_d operating like an “As^III-sponge” with unprecedented efficiency of 1800 mg As^III gr⁻¹. ZrMOF@SF_d consists of a neutral Zirconium Metal-Organic Framework [ZrMOF] covalently grafted on a natural silk-fiber (SF_d). ZrMOF itself exhibits As^III adsorption of 2200 mg gr⁻¹, which supersedes any -so far- known As^ΙΙΙ-sorbent. Using XPS, FTIR, BET-porosimetry data, together with theoretical Surface-Complexation-Modeling (SCM), we show that the high-As^ΙΙΙ-uptake is due to a sequence of two phenomena:[i] at low As^III-concentrations, surface-complexation of H₃AsO₃ results in As^III-coated voids of ZrMOF, [ii] at increased As^III-concentrations, the As^III-coated voids of ZrMOF are filled-up by H₃AsO₃via a partitioning-like mechanism. In a more general context, the present research exemplifies a mind-changing concept, i.e. that a “partitioning-like” mechanism can be operating for adsorption of metalloids, such as H₃AsO_3, by metal oxide materials. So far, such a mechanism has been conceptualized only for the uptake of non-polar organics by natural organic matter or synthetic polymers.

Rapid Preparation of TiO2-x and Its Photocatalytic Oxidation for Arsenic Adsorption under Visible Light

A rapid preparation method of TiO_2-x by thermal treatment using H₂TiO₃ as the precursor was proposed compared with the static hydrogenation thermal treatment process. Its adsorption properties of arsenic under visible light were explored and investigated as well. Various colors of TiO_2-x were prepared and characterized via XRD, TEM, BET, and so on. The results indicate that the method of rapid preparation is feasible. The TiO_2-x exhibits a larger particle size that varied from 10 nm to 2 μm, and deeper color products were obtained as the treatment temperature increased from 600 to 900 °C. Light yellow TiO_2-x was prepared after increasing the temperature from 600 to 900 °C, Ti₄O₇ and Ti₆O₁₁ with a dark color were formed under a H₂ atmosphere at 1500 °C. The arsenic adsorption performances of some samples under visible light were tested, and reveal a high efficiency of TiO_2-x in the photocatalytic oxidation arsenic adsorption under visible light, the conversion ratio of As(III) photocatalytic oxidation fluctuates around 2.85 mgAsg^-1 h^-1. In the absence of visible light, the adsorption capacities for As(III) and As(V) are 3.7 and 42.7 mg/g, respectively, at pH = 3. Under visible light condition, the adsorption capacity of As(III) increases sharply to 15.6 mg/g, which provides the foundation for a new application of TiO_2-x in the field of arsenic adsorption.

Rubber industry

Following chapter presents short introductory description of rubber and rubber industry. The main problem of rubber industry is the way of the usage of spent tires. Furthermore very important group of problems arise considering the metal and nonmetal additives which are significant component of the vulcanized rubber. The key attention is dedicated to typical ways of rubber usage in utilization and recovery of metals from spent rubber materials concentrating specifically on used tires processing. The method of recovery of rare metals from rubber tires was described. The rubber debris finds widest use in the field of waste metal solutions processing. The environmental pollution caused by metals poses serious threat to humans. Several applications of the use of waste rubber debris to remove metals from environmental waters were described. Moreover, the agriculture usage of waste tire rubber debris is described, presenting systems where the rubber material can be useful as a soil replacement.

Metals and metalloids treatment in contaminated neutral effluents using modified materials

Circumneutral surface water and groundwater can contain hazardous concentrations of metals and metalloids that can threaten organisms in surrounding ecosystems. Extensive research has been conducted over the past two decades to prevent, limit, and treat water pollution. Among the currently available treatment options is the use of natural and residual materials, which is generally regarded as effective and inexpensive. The modification of such materials enhances the removal capacity of metals and metalloids, as well as the physical and chemical stability of the materials and resulting sludge (after treatment). This paper reviews several modified materials that have produced and evaluated in the past twenty years to treat various contaminants in water under specific conditions. Important factors on performance improvement following the modifications are emphasized. Sorption capacity and kinetics, and element removal mechanisms are also discussed. Element recovery, material regeneration, water reuse, evaluation of treatment efficiency for real effluents are also considered, as well as the applicability of these materials in both active and passive treatment systems. Modified natural and residual materials are a promising option for the treatment of metals and metalloids in circumneutral contaminated waters. However, further research is necessary to evaluate their field-scale performance and to properly assess treatment costs.