New generation nano-adsorbents for the removal of emerging contaminants in water

Degradation kinetics, byproducts formation and estimated toxicity of metronidazole (MNZ) during chlor(am)ination

The residues of pharmaceuticals and personal care products (PPCPs) in environmental waters have been widespread concerned. Metronidazole (MNZ), normally employed to treat inflammation and infection, was chosen as one model PPCP. The degradation of MNZ by chlorination could be fitted by pseudo-first-order kinetics as the observed pseudo-first-order rate constants increasing from 0.0302 min^-1 to 0.2872 min^-1. However, the kinetics during chloramination of MNZ followed pseudo-second-order reaction, whose estimated half-live was approximately 6-8 times longer than chlorination. The chlor(am)ination of MNZ especially formed chloroform (CF), dicholoacetamide (DCAcAm), tricholoacetamide (TCAcAm) and dichloroacetonitrile (DCAN), and their yields were overall lower under chloramination than chlorination. During chlorination, the yield of CF was increased from 0.35 ± 0.02% to 2.06 ± 0.12% with 1-20 chlorine/MNZ molar ratio, whereas the formations of DCAcAm, TCAcAm and DCAN increased firstly and then decreased. Increasing chloramine dosage promoted the concentrations of scheduled disinfection byproducts (DBPs). CF and TCAcAm kept continuous generation in chlor(am)ination versus reaction time. Compared with the chlorination, the chloramination of MNZ was more dependent on pH value due to the self-degradation of chloramine. Faintly acidic condition favored N-DBPs' formation in MNZ when it was subjected to chlor(am)ination. The chloramination of MNZ produced cytotoxicity and genotoxicity by 10-15 folds lower than chlorination, and DCAN formed during chloramination dominated both DBPs' yields and toxicity contribution. Opposite to chlorination, the integrated toxicity of MNZ during chloramination varied linearly versus N-DBPs' yields.

Indolocarbazole based polymer coated super adsorbent polyurethane sponges for oil/organic solvent removal

The synthesis of an indolocarbazole-fluorene based conjugated polymer (ICZP6), by Sonogashira coupling reaction, has been presented. The ICZP6 has then been integrated with a nano iron oxide embedded polyurethane foam (ICZP6PUF) to develop a promising adsorbent for oil/organic contaminants in aqueous systems. The anchoring ability of ICZP6 on to iron oxide PU sponge switches on significant hydrophobicity within the whole molecular assembly. The cooperative effects of ICZP6-iron oxide- PU sponge system have been highlighted in terms of structural, microscopic and wettability characteristics. The heterogeneity and hierarchical porous structure of the system offer a high adsorption capability for different types of oils and organic contaminants in water, typically in the range of 100-240 gg^-1. The performance of ICZP6PUF has been confirmed by the fast (within 5-10s) and choosy removal of selected oils and organic solvents from polluted water with the aid of an external magnetic field. The adsorbed materials (oil/organic solvents) can be separated from the adsorbent by simple mechanical squeezing without causing any structural deformation or performance deterioration; with a reusability of the system over 50 cycles. The adsorption isotherm has been found to fit well with the Langmuir model with R² = 0.9484. To extent the scope of the ICZP6PUF hybrid, an integrative logic gate has been designed.

TiO2/S-Doped Carbons Hybrids: Analysis of Their Interfacial and Surface Features

Hybrids containing approximately equal amounts of P25 TiO₂ and S-doped porous carbons were prepared using a water-based slurry mixing method. The materials were extensively characterized by adsorption of nitrogen, potentiometric titration, thermal analysis in air and in helium, XRD, XPS and SEM. The collected results showed the significant blockage of carbon micropores by TiO₂ particles deposited on their outer surface. The formation of a new interface, especially for the S-rich samples, might also contribute to the porosity alteration. Analysis of surface chemistry suggested the presence of Ti-S bonds with an involvement of sulfur from thiophenic species in the carbon phase. The latter, especially when polymer-derived, was mainly deposited on the TiO₂ nanoparticles. Formation of Ti-S stabilized sulfur and increased the ignition temperature of the hybrids, especially those with a high content of sulfur, in comparison with the ignition temperature of carbons. The surfaces of hybrid with S-containing carbons was also thermally very stable and of basic chemical nature. The formation of interfacial structures Ti-C was detected by XPS analysis suggesting a partial reduction of the Ti.

Emerging pollutants-Part II: Treatment

Recently, emerging pollutants (EPs) have been frequently detected in urban wastewater, surface water, drinking water, and other water bodies. EPs mainly usually include pharmaceuticals and personal care products, endocrine-disrupting chemicals, antibiotic resistance genes, persistent organic pollutants, disinfection by-products, and other industrial chemicals. The potential threat of EPs to ecosystems and human health has attracted worldwide attention. Therefore, how to treat EPs in various water bodies has become one of the research priorities. In this paper, some research results on treatment of EPs published in 2018 were summarized. PRACTITIONER POINTS: At present, more attention has been paid to emerging pollutants (EPs), including pharmaceuticals and personal care products (PPCPs), endocrine-disrupting chemicals (EDCs), antibiotic resistance genes, persistent organic pollutants, disinfection by-products, etc. Existing EPs disposal technologies mainly include: engineered wetlands and natural systems, biological treatment, physical and physicochemical separation, chemical oxidation, catalysis, etc. This paper reviews some research results on the treatment technologies of EPs published in 2018.

Application of Composite NanoMaterial to Determine Phenols in Wastewater by Solid Phase Micro Membrane Tip Extraction and Capillary Electrophoresis

Composite nanoparticles were used in solid phase micro membrane tip extraction and capillary electrophoresis to determine phenol and p-amino-phenol in wastewater. The optimized conditions were 100 g/L concentration, 40 min contact time, 11 pH, 5 mg/mL nanoparticles amounts, 60 min desorption time, 9 desorption pH and 298 K temperature. Capillary electrophoresis conditions were phosphate buffer (15 mM, pH 7.0) background electrolyte, 18 kV applied voltage, 214 nm UV detection, 30 s sample loading at 23 ± 1 °C. The maximum percent uptakes of p-amino-phenol and phenol were 80.0 and 85.0%. High ratio recoveries of p-amino-phenol and phenol from nanomaterial were 99.0 and 98. Consequently, the actual extractions of p-amino-phenol and phenol from wastewater were 79.2 and 83.30 percent. The migration times of phenol and p-amino-phenol and were 9.0 and 12.0 min. The detection limits of phenol and p-amino-phenols were 0.1 and 0.2 µg/L after extraction and CE. Therefore, this combination of solid phase micro membrane tip extraction and capillary electrophoresis may be considered as the ideal one for monitoring of toxic phenol and p-amino-phenol in water sample.

Preparation and regeneration of iron-modified nanofibres for low-concentration phosphorus-containing wastewater treatment

In this study, nanocellulose (CNFs) was prepared by a mechanical shearing method, a simple and pollution-free process. Iron hydroxide was loaded on nanocellulose, a natural macromolecule derived from bamboo, to produce the second-generation iron-loaded nanocellulose for the removal of low-concentration phosphorus from wastewater. We found that the best modified ferric salt was ferric chloride. When the mass ratio of Fe(OH)3 and CNFs was 1.5 : 1, freeze-drying with liquid nitrogen yielded the best adsorption performance. The adsorption process of Fe(OH)3@CNFs followed the pseudo-second-order kinetics and belonged to chemical adsorption. Regeneration experiments showed that after 10 cycles of adsorption-regenerations of the adsorbent, the phosphorus adsorption efficiency was still stable at 80% of the initial material. The prepared adsorbent was characterized by the BET surface area measurement, scanning electron microscopy and FT-IR. The surface morphology, pore size and elements of materials before and after iron loading were analysed. Compared with other adsorbents, the phosphorus removal performances of the second-generation iron-loaded nanocellulose were superior. Compared with the first-generation material, the second-generation adsorbent is simpler and more environmentally friendly.

Effective and reusable nano-silica synthesized from barley and wheat grass for the removal of nickel from agricultural wastewater

In the present study, a comparative analysis was performed on the extraction of nickel ions (Ni²⁺) from agricultural wastewater using nanosilica (NS) synthesized from barley (NS-B) and wheat (NS-W) grass waste with a yield of 92.4%. The experimental procedure was conducted on barley and wheat waste to obtain an 85% pure NS that served as the adsorbent for nickel extraction in wastewater. The NS was characterized and studied using X-ray fluorescence (XRF), which demonstrated that NS synthesized from barley contained 94.2% SiO₂, while NS synthesized from wheat contained 93.0% SiO₂. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to determine the surface morphology of the nanoparticles. The energy-dispersive X-ray (EDX) analysis and Fourier transform infrared (FTIR) analysis were used to determine the elements and functional groups of the synthesized particles, respectively. Lastly, particle size and surface area analyses were performed using the Brunauer-Emmett-Teller (BET) method, which determined that the nanoparticles were 70 and 102 nm for NS-B and NS-W, respectively. The adsorption of nickel ions from agricultural wastewater was studied at various concentrations (10-200 mg/L). The kinetic models indicate that sorption equilibrium time was 65 min and that the reaction followed the pseudo-first-order kinetics model with a regression coefficient (R²) of 0.9289. Corresponding studies indicated that the Freundlich isotherms best describe the sorption reaction with an R² value of 0.9958, which indicates the multilayer adsorption of nickel on the adsorbent. In their standard and real states, the samples indicated that NS-B and NS-W provided high levels of nickel (Ni²⁺) removal at 95 and 90%, respectively.

Unusual behavior of MgFe2O4 during regeneration: desorption versus specific adsorption

The reusability of spent adsorbents is the most important characteristic for their practical application. The process of MgFe₂O₄ regeneration after methylene blue (MB) adsorption was studied. The effect of the nature (HCl, HNO_3, and MgCl₂) and the concentration (10^-3-10^-1 M) of regeneration agents was established. All the regeneration agents at 10^-3 and 10^-2 M had high efficiency and adsorption capacity recovery reached 80-90%, whereas for 10^-1 M concentration the adsorption efficiency was in the range of 4.5-36.2%. It was shown that the concentration of desorbed MB was much less than what had been previously adsorbed and did not correlate with regeneration efficiency. The unusual behavior of MgFe₂O₄ during regeneration could be due to different mechanisms of regeneration by OH₃ ⁺ and Mg²⁺ ions: (i) for acidic regeneration the main process was the non-specific adsorption of OH₃ ⁺ ions in a diffusion layer and the substitution of adsorbed MB due to electrostatic forces; (ii) in the case of Mg²⁺ as a regeneration agent, there was specific adsorption due to the completion of a crystal lattice of MgFe₂O₄ nanoparticles by Mg²⁺ ions (according to the rules of Fayans-Pannet) with the formation of new Mg-OH adsorption sites and the super-equivalent adsorption of Mg²⁺ ions (according to DLVO (Derjaguin, Landau, Verwey, and Overbeek) theory) accompanied by a recharge of the MgFe₂O₄ surface. These phenomena of MgFe₂O₄ regeneration using Mg²⁺ ions must be taken into account in the theory and practice of adsorption.

Elimination performance of methylene blue, methyl violet, and Nile blue from aqueous media using AC/CoFe2O4 as a recyclable magnetic composite

The present paper describes the sono-assisted adsorption (sono-adsorption) of methylene blue (MB), methyl violet (MV), and Nile blue (NB) from aqueous solution by AC/CoFe₂O₄ magnetic composite. FT-IR, TGA-DTG, VSM, XRD, TEM, SEM, EDX, Map, and Raman analysis were used to characterize the magnetic composite. The magnetization saturation value of AC/CoFe₂O₄ magnetic composite was determined to be 53.06 emu/g. Dye sono-adsorption efficiency was increased by increasing adsorbent dose, pH value, and contact time, but not dye concentration. Pseudo-first-order, pseudo-second-order, and intra-particle diffusion models were used to study the kinetic behavior of the cationic dye sono-adsorption. The sono-adsorption kinetics was reasonably followed by pseudo-second-order model (R² > 0.998). The results showed that the Freundlich model (R² > 0.976) was more able to describe the sono-adsorption equilibrium behavior than Langmuir, D-R, and Scatchard models. The maximum sono-adsorption capacity of NB, MV, and MB was determined as 86.24, 83.90, and 87.48 mg/g, respectively. Based on the parameters derived from isotherm modeling (R_L, n, and E), the sono-adsorption process of cationic dyes is desirable and physical. An increase in NaCl concentration reduced the sono-adsorption efficiency for all dyes. Also, the adsorption-desorption of AC/CoFe₂O₄ magnetic was studied up to 10 stages, and it was confirmed that the sono-adsorption efficiency is acceptable up to the eight stage. AC/CoFe₂O₄ magnetic composite is, therefore, an affordable and recyclable adsorbent to remove the molecule of NB, MV, and MB dyes from aqueous media.

Graphene based adsorbents for remediation of noxious pollutants from wastewater

The contamination of water resources with noxious pollutants is a serious issue. Many aquatic systems are contaminated with different toxic inorganic and organic species; coming to wastewater from various anthropogenic sources such as industries, agriculture, mining, and domestic households. Keeping in view of this, wastewater treatment appears to the main environmental challenge. Adsorption is one of the most efficient techniques for removing all most all types of pollutants i.e. inorganics and organics. Nowadays, graphene and its composite materials are gaining importance as nano adsorbents. Graphene; a two-dimensional nanomaterial having single-atom graphite layer; has attracted a great interest in many application areas (including wastewater treatment) due to its unique physico-chemical properties. The present paper is focused on the remediation of noxious wastes from wastewater using graphene based materials as adsorbents, and it contains all the details on materials - i.e., from their synthesis to application in the field of wastewater treatment (removal of hazardous contaminants of different chemical nature - heavy and rare-earth metal ions, and organic compounds - from wastewater effluents. The efficiency of the adsorption and desorption of these substances is considered. Certainly, this article will be useful for nano environmentalist to design future experiments for water treatment.

Sustainable Graphene Aerogel as an Ecofriendly Cell Growth Promoter and Highly Efficient Adsorbent for Histamine from Red Wine

The utilization of a sustainable and lightweight graphene aerogel (GA), synthesized from crude biomass, as a cell growth promoter and an adsorbent for the efficient removal of histamine (HIS), a food toxicant, from the real food matrix has been explored. Due to the self-supported three-dimensional nanoporous honeycomb-like structure of the graphene framework and the high surface area, the synthesized GA achieved an 80.69 ± 0.89% removal of HIS from red wine (spiked with HIS) after just 60 min under both acidic (3.0) and neutral (7.4) pH conditions. Furthermore, simple cleaning with 50% ethanol and deionized water, without any change in weight, allowed them to be reused more than 10 times with a still significant HIS removal ability (more than 71.6 ± 2.57%). In vitro cell culture experiments demonstrated that the synthesized GA had nontoxic effects on the cell viability (up to 80.35%) even at higher concentrations (10 mg mL^-1), as determined via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and lactate dehydrogenase assays using human lung bronchial epithelial cells. Interestingly, GA promotes the wound-healing ability on the scratched epithelial cell surfaces via enhancing the cell migrations as also validated by the western blot analysis via expression levels of epithelial β-catenin and E-cadherin proteins. The distinct structural advantage along with the nontoxicity of the green synthesized GA will not only facilitate the economic feasibility of the synthesized GA for its practical real-life applications in liquid toxin and pollutant removal from the food and environment but also broaden its applicability as a promising biomaterial of choice for biomedical applications.

Preparation of a carboxymethylcellulose-iron composite for uptake of atorvastatin in water

Many water bodies are being contaminated by atorvastatin, which has certain side effects and problems on healthy individuals through contaminated water. For this purpose, effective and selective carboxymethylcellulose macromolecule iron composite nanoparticles were synthesized by green methods, characterized and used for uptake of atorvastatin drug residue from water. Atorvastatin in water was analyzed by HPLC using Aqua C₂₈ (250 mm × 46 mm id) column and buffer-ACN (35:65, v/v) as eluent. The maximum elimination of atorvastatin was 80% with 40 μg L^-1 concentration; 40 min agitated time, 5.0 pH, 1.0 g L^-1 dose and 298 K temp. The removal data obeyed Freundlich, Langmuir, Dubinin-Radushkevich and Temkin models. The values of free energy were -8.79, -8.73 and -8.65 kJ mol^-1 at 20.0, 25.0 and 30.0 °C temperatures. Enthalpy value was -14.16 kJ mol^-1; showing exothermic removal. Entropy was -18.74 × 10^-3 kJ mol^-1 K; presenting decrease in entropy in the process. The kinetics modeling showed pseudo-first-order and liquid film diffusion mechanisms of removal. The removal technology was quick, conservation pleasant and lucrative. It is because of it capability with little dose and interaction time. Hence, the reported technology is practical for the exclusion of atorvastatin in water resource.

Modeling of fenuron pesticide adsorption on CNTs for mechanistic insight and removal in water

Inexpensive multi-walled carbon nanotubes (MCNTs) were prepared with 10-40 nm particle sizes and 9.0 m²g^-1 surface area. Fenuron pesticide was removed in water using these CNTs with 100.0 µgL^-1 concentration, 60 min contact time, 2.0 g L^-1 dose, 7.0 pH, and 25 °C. 90% removal of fenuron pesticide was achieved. Adsorption data obeyed Tempkin, Freundlich, Langmuir and Dubinin-Radushkevich models. The standard free energies values of fenuron pesticide adsorption were -11.89, -11.59, -11.55 kJ mol^-1. The values of enthalpy and entropy were -9.12 kJmol^-1 and -26.61 × 10^-3 kJ mol^-1 K. The negative values of free energy showed speedy adsorption of fenuron pesticide on CNTs. The supramolecular mechanism of fenuron adsorption onto CNTs was fixed by simulation studies and the binding energy and binding affinity of fenuron with CNTs were - 6.5 kcal mol^-1 and 5.85 × 10⁴ M^-1, respectively. There were one π-σ, seven π-π stacked, one π-π T-shaped, and three π-alkyl type of hydrophobic interactions between fenuron and carbon nanotube. These results clearly indicated the physical nature of the adsorption. The method is speedy, cost-effective, efficient and repeatable. Therefore, the established adsorption method is appropriate for adsorption of fenuron pesticide in waters.

Arsenic surface complexation behavior in aqueous systems onto Al substituted Ni, Co, Mn, and Cu based ferrite nano adsorbents

The present study is about surface complexation behavior of arsenic species adsorbed onto ternary metal oxide adsorbents (Ni-Al-Fe, Co-Al-Fe, Mn-Al-Fe, and Cu-Al-Fe). The analysis is carried out by X-ray absorption spectroscopy (XAS) tool. XANES (μ(E) vs. E) spectra close to the absorption edge (i.e., As K-edge) of all samples are observed along with the As(III) and As(V) standards. The first derivative of XANES for Ni-As(V), and Cu-As(V) samples agree with that of As(V) standards, respectively. Whereas, As(III) adsorbed adsorbent systems (i.e., Ni, Co, Mn, and Cu) are observed with mixed oxidation state of arsenic. A total of 65-85 % is observed with initial oxidation state (As(III) or As(V)), and remaining 15-35 % is observed with modified oxidation state (As(V) or As(III)) that explains the occurrence of possible charge transfer. EXAFS analysis shows the As-O bond distances in the range of 1.7-1.8 Å. The corresponding As-M bond distances are around 2.7, 3.2, and 3.6 Å which confirms the formation various edge sharing (²E), and corner sharing (²C, ¹V) surface complexes. Surface coverage is understood as an important parameter as bidentate attachments (²E, ²C) are evident in As(III), and As(V), but monodentate attachments (¹V) are only observed in As(V).

Ethylene glycol-assisted fabrication and superb adsorption capacity of hierarchical porous flower-like magnesium oxide microspheres for phosphate

Hierarchical porous flower-like MgO microspheres were fabricated via an ethylene glycol-assisted route under mild conditions and exhibited an outstanding maximum adsorption capacity of 574.71 mg g⁻¹ for phosphate.

Adsorption of ionic liquids onto an activated carbon: kinetic modeling studies

In this study, the uptake of hydrophobic bromide-based ionic liquids (ILs) (imidazolium, pyrrolidinium, and pyridinium) from aqueous solutions onto granulated and fabric-based microporous activated carbons (ACs). Surface characterization study shows that both ACs have basic pHpzc, like 8.7 for granulated AC and 8.0 for fabric AC. Granulated AC have ten times higher phenolic groups 0.2 meq g^-1 compared to fabric AC which is 0.03 meq g^-1. The kinetics of adsorption was remarkably slower for ILs on granulated/fabric AC than milled one. We also studied the effect of AC size on the rate of adsorption in the operating conditions. In order to improve the adsorption kinetics of ILs with ACs, different phenomenological and empirical kinetic models like as pseudo-first order, Boyd model, pseudo-second-order diffusion model and Elovich were applied on the kinetic experimental data. The analysis of kinetic specified that the adsorption mechanism of ILs onto ACs is controlled mainly by the mass transfer through the pores of ACs. So, the selection of appropriate adsorbent particle size of AC plays a main role for the development of viable IL adsorption. Graphical abstract ᅟ.

Quantitative contribution of Cd2+ adsorption mechanisms by chicken-manure-derived biochars

This study investigated the efficiency and mechanisms of Cd²⁺ removal by chicken-manure biochar produced at different temperatures. Adsorption kinetics, isotherms, thermodynamic, and desorption were examined, and the biochars before and after adsorption were analyzed by SEM-EDS, FTIR, Boehm titration, and XRD. Kinetics of adsorption were better described by pseudo-second-order kinetic model than pseudo-first-order kinetic and intraparticle diffusion model under different initial Cd²⁺ concentrations of 20, 50, and 100 mg L^-1. Equilibrium adsorption was better modeled by Freundlich and Temkin isotherm equations than Langmuir equation at different temperatures of 25, 35, and 45 °C. Thermodynamic parameters confirmed the spontaneous and endothermic nature of the adsorption of Cd²⁺ at all of temperatures. Moreover, functional group complexation, precipitation, and cation exchange jointly contributed to Cd²⁺ adsorption on the biochars, whose relationship with the properties of biochar were also analyzed. The new precipitate as Cd₅(PO₄)₃OH was found during the adsorption. Complexation and precipitation were predominant mechanisms for all biochars (together accounting for 92.4-98.8%), while cation exchange made a relatively minor contribution to total Cd²⁺ removal (accounting for 1.2-7.6%). The relative distribution of each mechanism on the biochars was determined, which deepen our understanding of the Cd²⁺ adsorption process. These results are useful for future practical applications of biochar to removal heavy metals from water.

Improvement of activated carbon characteristics by sonication and its application for pharmaceutical contaminant adsorption

Sonicated activated carbon (SAC) was developed and used to remove ibuprofen and ketoprofen from aqueous media by adsorption. A standard activated carbon sample (AC) was used as comparison. Both adsorbents were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), N₂ adsorption isotherms (Brunauer, Emmett, and Teller (BET)), helium gas pycnometry, and scanning electron microscopy (SEM). In the adsorption study, kinetics, equilibrium, and thermodynamics were evaluated. SAC presented better characteristics than AC. Pseudo-second-order model was adequate to predict the kinetic curves. The isotherm data obeyed the Sips model. Thermodynamic results revealed a spontaneous and endothermic process, where physisorption was involved. The maximum adsorption capacities of SAC were 134.5 and 89.2 mg g^-1 for ibuprofen and ketoprofen, respectively. For AC, the maximum adsorption capacities were 115.1 and 79.1 mg g^-1 for ibuprofen and ketoprofen, respectively. The sonication technique presented great potential to improve the AC characteristics, generating a promising material (SAC) for ibuprofen and ketoprofen adsorption.

Review on recent progress in chitosan-based hydrogels for wastewater treatment application

Recently, chitosan has been used as a raw material for synthesis of hydrogels in a wide range of potential and practical applications like wastewater treatment, drug delivery, and tissue engineering. This review represents an overview of the application of chitosan-based hydrogels for wastewater treatment and helps researchers to better understand the potential of these adsorbents for wastewater treatment. It covers recently used and prospected methods for synthesis and modification of these hydrogels. Chitosan-based hydrogels are modified physically and chemically through crosslinking, grafting, impregnation, incorporating of hard fillers, blending, interpenetrating, and ion-imprinting methods to improve adsorption and mechanical properties. Understanding of these methods provides useful information in the design of efficient chitosan-based hydrogels and the select of appropriate pollutants for removal. This review provides a brief outlook on future prospects of chitosan-based hydrogels for wastewater application.