Melamine, which has three free amino groups and three aromatic nitrogen atoms in its molecule, can be potentially used as an adsorbent for metal ions. Factors associated with adsorption efficiency of vanadium by melamine were systematically investigated, including initial pH value of solution, temperature, contact time, and dosage of melamine. The optimal operation conditions for adsorption performance of vanadium with melamine were obtained. The adsorption efficiency was over 99.97% at the initial pH value of 1.18, molar ratio of n (melamine)/n (vanadium) = 1.0 for 60 min. The kinetic data for the adsorption followed well the pseudo second-order kinetic model.

This study assessed the level of potentially toxic trace metals (PTMs), seasonal variations, and their possible sources from the surface water and lake-bed sediment of Panchpokhari lake series, an alpine and glacial lake at 4160 m a.s.l. in Central Nepal. The lake series have five lakes, with Lake-1 larger than others. So, Lake-1 was investigated thoroughly during pre-monsoon and post-monsoon seasons. Sediment core was collected from the deepest basin of the Lake-1 during pre-monsoon. Most of the PTM concentrations were higher in the pre-monsoon season; however, Sc, Cr, Cu, Zn, As, and Ag were higher in the post-monsoon. This is an indication that the lake has been impacted either by natural or long-range transported atmospheric pollutants. Ti, Sb, and Ag had extremely high enrichment factor (EF) in waters, whereas Cd, Zn, and As had high EF in sediments indicating that these metals originated from anthropogenic sources. Furthermore, PTM concentrations in the sediment were in the increasing order of Hg < Cd < Ag < Mo < Sb < Sn < As < U < Sc < Co < Cs < Cu < Pb < Ni < Cr < V < Zn < Rb < Mn < Ti < Fe and showed that the upper layer (top 10 cm) of lake sediment has been receiving a higher load of PTMs in the recent period. he observed EF values also suggested that major sources of PTMs in the sediment were from crustal origin except for a few metals (Ti, V, Sb, and Ag) which were enriched anthropogenically due to long-range transport of atmospheric pollutants, deposited at the higher elevations. Nevertheless, the level of pollution in sediments was low as indicated both by EF and geo-accumulation index.

Adsorption of hexavalent chromium (Cr(VI)) using pomelo peel activated biochar (PPAB) as a adsorbent was investigated. The characterization of the adsorbent was studied by Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and zeta potentials analysis. The results showed that the PPAB had a high microporous structure and the existence of organic compounds such as hemicellulose, cellulose, and lignin. Various parameters including initial Cr(VI) concentration, pH, and adsorbent dosage were studied. The results indicated that the adsorption process was pH dependent and maximum adsorption capacity of Cr(VI) was 57.637 mg/g at pH 2.0 and 35 °C with PPAB dosage of 0.05 g. The adsorption kinetics fitted well to the pseudo-second-order model and the correlation coefficients were greater than 0.999. The adsorption isotherm data could be better described with the Langmuir model, suggesting the homogeneous and monolayer adsorption. Moreover, the scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and Fourier transform infrared spectrum (FTIR) results showed that the surface of PPAB had plenty of developed pores after activation and the modification process was deemed to proceed between the O–H groups from pomelo peel and H₃PO₄ molecules. The main adsorption mechanism was attributed electrostatic interaction and ion exchange between the surface of PPAB and Cr(VI).

The objective of this research was to evaluate the biodegradation of chloroform by using biotrickling filter (BTF) and determining the dominant bacteria responsible for the degradation. The research was conducted in three phases under anaerobic condition, namely, in the presence of co-metabolite (phase I), in the presence of co-metabolite and surfactant (phase II), and in the presence of surfactant but no co-metabolite (phase III). The results showed that the presence of ethanol as a co-metabolite provided 49% removal efficiency. The equivalent elimination capacity (EC) was 0.13 g/(m³ h). The addition of Tomadol 25-7 as a surfactant in the nutrient solution increased the removal efficiency of chloroform to 64% with corresponding EC of 0.17 g/(m³ h). This research also investigated the overall microbial ecology of the BTF utilizing culture-independent gene sequencing alignment of the 16S rRNA allowing identification of isolated species. Taxonomical composition revealed the abundance of betaproteobacteria and deltaproteobacteria with species level of 97%. Azospira oryzae (formally dechlorosoma suillum), Azospira restrica, and Geobacter spp. together with other similar groups were the most valuable bacteria for the degradation of chloroform.

Phytoremediation using vetiver grass (Vetiveria zizanioides) has been regarded as an effective technique for removing contaminants in polluted water. This study was conducted to assess the removal efficiency of heavy metals (Cu, Fe, Mn, Pb, Zn) using vetiver grass (VG) at different root lengths and densities and to determine metals uptake rate by plant parts (root and shoot) between treatments (low and high concentration). Removal efficiency for heavy metals in water by VG is ranked in the order of Fe>Pb>Cu>Mn>Zn. Results showed that VG was effective in removing all the heavy metals, but removals greatly depend on root length, plant density and metal concentration. Longer root length and higher density showed greater removals of heavy metals due to increased surface area for metal absorption by plant roots. Results also demonstrated significant difference of heavy metals uptake in plant parts at different concentrations indicating that root has high tolerance towards elevated concentration of heavy metals. However, the effects were less significant in plant shoot suggesting that metals uptake were generally higher in root than in shoot. The findings have shown potential of VG in phytoremediation for heavy metals removal in water thus providing significant implication for treatment of metal-contaminated water.

To remove heavy metal contaminations from road runoff prior to discharge into surface water or groundwater, highly porous sorptive filter materials are used. One effective material is a technical product based on granular ferric hydroxide. To specify the removal mechanisms, lab-scale column experiments were performed preloading the material with Cd, Cu, Ni, Pb, and Zn. To identify removal mechanisms and the distribution of heavy metals in the material, investigations with scanning electron microscope (SEM)/energy-dispersive X-ray spectroscopy (EDX) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were performed. With SEM/EDX, only Pb was detectable; all other heavy metals were not represented on the surface of the particles. To determine the intrusion of the metals, LA-ICP-MS was used. Thereby, the high porosity necessitated a special data evaluation that enabled the determination of the heavy metal removal and the leaching of other elements from the filter material as a function of depth. The measured depth profiles varied for each element and correlated with the metal mobility.

In this paper, quaternized β-cyclodextrin–montmorillonite composite (QCD-MMT) was obtained and absorption properties of Cr(VI), methyl orange and p-nitrophenol were studied. QCD was prepared by 2,3-epoxypropyltrimethylammonium chloride and β-cyclodextrin (β-CD). QCD-MMT was obtained by reaction between QCD and montmorillonite suspensions, which could be attributed to the montmorillonite cation ion exchange properties. β-CD cavities of this composite were expected to capture organic molecules through inclusion, while montmorillonite units acted as the adsorption sites for metals. QCD-MMT was characterized by FT-IR, elemental analysis, XRD, SEM-EDX, and TGA. Adsorptions of Cr(VI), methyl orange, and p-nitrophenol were highly dependent on adsorbent dose, initial concentration, temperature, contact time, and pH. Adsorption kinetics of Cr(VI), methyl orange, and p-nitrophenol followed the pseudo-second-order model. Meanwhile, adsorption of Cr(VI) fit better in the Freundlich model, inferring a multilayer adsorption, while the adsorption of methyl orange and p-nitrophenol fit better in Langmuir model, inferring a monolayer adsorption. Thermodynamic analysis showed that the adsorptions were all endothermic process and could be spontaneous at given temperature range, except for Cr(VI), of which adsorption should be at much higher temperature. Overall, QCD-MMT exhibited potential for practical applications in the treatment of both metal ions and organic pollutants.

The effect of styrene-divinylbenzene copolymer functionalization by carboxylic acid groups on the adsorption of p-nitrophenol (p-NP) from aqueous solutions was investigated. The adsorption capacity of p-NP onto the functionalized copolymer (CP-F) was compared with that of the precursor copolymer, the chloromethylated styrene-divinylbenzene copolymer (CP-N). The two copolymers were characterized by Fourier transform infrared (FTIR) spectroscopy, thermal analysis (DSC-TG), specific surface area and particle size measurements, pore size distribution, scanning electron microscopy (SEM), and elemental analysis (EDX). The adsorption of p-NP was substantially enhanced after the polymer functionalization, and it was demonstrated that hydrogen bonding is principally responsible for the high adsorption capacity of CP-F in comparison with CP-N. The adsorption kinetics of p-NP adsorption onto CP-F was well described by the pseudo-second-order model. From the four investigated isotherms, Langmuir, Freundlich, Redlich-Peterson, and Sips, the equilibrium data were better described by the Sips model. The maximum adsorption capacity of the CP-F polymer resulting from the Sips isotherm was 243.37 mg g⁻¹. The capacity of regeneration and reuse of the CP-F polymer was evaluated in three consecutive cycles of adsorption-desorption.

In order to explore the synthesis of silicate-1 membrane on kaolin clay ceramic and the effect of Na⁺ ion substitution on the dielectric properties of ceramic, silicate-1@kaolin clay ceramics containing different content of Na⁺ were successfully synthesized by combining sintering, sol-gel, and ion exchange method. Samples were analyzed by chemical composition (XRF), X-ray diffraction (XRD), scanning electron microscope (SEM), digital hardness tester, and microwave dielectric measurement system. SEM images exhibited that a layer of silicate-1 was successfully grown on the surface of the kaolin clay ceramic. The energy dispersive spectrometer (EDS) revealed that the content of Na⁺ in silicate-1 decreased with increase of ion exchange time. The content of Na⁺ in silicate-1@kaolin clay ceramic decreased from 1.46 to 0.29% when the silicate-1@kaolin clay ceramic was treated by the unsaturated solution of NH₃ from zero to two times. In this process, the dielectric constant of the silicate-1@kaolin clay ceramic almost kept the same. But the dielectric loss of silicate-1@kaolin clay ceramic decreased from 0.474 to 0.131. Silicate-1@kaolin clay ceramic is expected to be used as sensor to detect some metal ions.

The aim of this study was to evaluate the genotoxic and mutagenic potential of contaminated soil diluted in acidic solutions and not acidic, in the offspring of rats exposed during pregnancy and neonatal periods. To this end, a comet assay and micronucleus test were performed. Soil samples were solubilized in the following three solvents: distilled water (control group), acid solvent at pH 5.2, and acid solvent at pH 3.6. Soil and solvent were mixed in a rate of 1:2 in g/mL, and hydrofluoric acid was used in the acid solvents. In the comet assay, the tail length, percentage of DNA within the tail and tail moment was analyzed in the whole blood of the pups that were studied. The number of micronuclei found in the bone marrow cells was counted in the micronucleus test. In all parameters evaluated in the comet assay, the group exposed to the lowest pH value when associated with contaminated soil (p < 0.05) had the most damage. However, the micronucleus test showed differences between all exposed groups and the control group (p < 0.05). These results reaffirm the health risks related to the exposure to soil contaminants.