Engineered nanoparticles for removal of pollutants from wastewater: Current status and future prospects of nanotechnology for remediation strategies

Significant aspects of the world\u27s water scenario, primarily associated with global population growth and climate change, necessitate new technology implementation to ensure a supply of drinking water and prevent global water contamination. In light of this, the incorporation of state-of-the-art nanotechnology in conventional process engineering opens new paths for improved wastewater treatment technologies. Nano-based materials techniques, such as disinfection, desalination, sensing and monitoring, photocatalysis, membrane process, adsorption, biological treatment, coagulation/precipitation, and oxidation are discussed in this overview of current breakthroughs in nanotechnologies for removal of pollutants from wastewater. The benefits of these nano-based materials for wastewater treatment approaches, as well as the technical challenges are discussed in this review. The current state of commercialization, as well as future research opportunities in nano-based materials and technologies are highlighted. Additionally, the anticipated scientific breakthroughs, the constraints of nanotechnology for desalination processes, such as rules and regulations, and potential health risks are addressed. The regulation of nanoengineered materials and technologies used in wastewater treatment is being addressed in both Europe and United States of America

High interfacial charge separation in visible-light active Z- scheme g-C3N4/MoS2 heterojunction: Mechanism and degradation of sulfasalazine

Examination of highly proficient photoactive materials for the degradation of antibiotics from the aqueous solution is the need of the hour. In the present study, a 2D/2D binary junction GCM, formed between graphitic-carbon nitride (g-C3N4) and molybdenum disulphide (MoS2), was fabricated using facile hydrothermal method and its photo-efficacy was tested for the degradation of sulfasalazine (SUL) from aqueous solution under visible-light irradiation. Morphological analysis indicated the nanosheets arrangement of MoS2 and g-C3N4. The visible-light driven experiments indicated that 97% antibiotic was degraded by GCM-30% within 90 min which was found to be quite high than pristine g-C3N4 and MoS2 at solution pH of 6, GCM-30% dose of 20 mg, and SUL concentration of 20 mgL-1. The degradation performance of GCM-30% was selectively improved due to enhanced visible-light absorption, high charge carrier separation, and high redox ability of the photogenerated charges which was induced by the effective Z-scheme 2D/2D heterojunction formed between g-C3N4 and MoS2. The reactive radicals as determined by the scavenging study were •O2-, and h+. A detailed degradation mechanism of SUL by GCM-30% was also predicted based on the detailed examination of the band gaps of g-C3N4 and MoS2

Emerging contaminants of high concern for the environment: Current trends and future research

Wastewater is contaminated water that must be treated before it may be transferred into other rivers and lakes in order to prevent further groundwater pollution. Over the last decade, research has been conducted on a wide variety of contaminants, but the emerging contaminants are those caused primarily by micropollutants, endocrine disruptors (EDs), pesticides, pharmaceuticals, hormones, and toxins, as well as industrially-related synthetic dyes and dye-containing hazardous pollutants. Most emerging pollutants did not have established guidelines, but even at low concentrations they could have harmful effects on humans and aquatic organisms. In order to combat the above ecological threats, huge efforts have been done with a view to boosting the effectiveness of remediation procedures or developing new techniques for the detection, quantification and efficiency of the samples. The increase of interest in biotechnology and environmental engineering gives an opportunity for the development of more innovative ways to water treatment remediation. The purpose of this article is to provide an overview of emerging sources of contaminants, detection technologies, and treatment strategies. The goal of this review is to evaluate adsorption as a method for treating emerging pollutants, as well as sophisticated and cost-effective approaches for treating emerging contaminants

Constructing Z-scheme LaTiO\u3csub\u3e2\u3c/sub\u3eN/g-C\u3csub\u3e3\u3c/sub\u3eN\u3csub\u3e4\u3c/sub\u3e@Fe\u3csub\u3e3\u3c/sub\u3eO\u3csub\u3e4\u3c/sub\u3e magnetic nano heterojunctions with promoted charge separation for visible and solar removal of indomethacin

© 2020 Elsevier Ltd Pharmaceutical effluents in water bodies pose hazards to the ecosystem because of their potent biological toxicity. Focusing on the removal of such toxic complicated pharmaceutical residues, an innovative LaTiO2N/g-C3N4@Fe3O4 heterojunction photocatalyst was assembled by a simplistic route for visible and solar light degradation of anti-inflammatory drug indomethacin (IDM). The LCF-20 catalyst (with LaTiO2N:g-C3N4 -0.2:1) shows excellent performance for visible light photodegradation of IDM, as evidenced by 97.3 % removal in just 45 min exposure which is about 13 times faster than bare g-C3N4. 83.4 % of total organic carbon removal was achieved by LVF-20 under visible light. Also, with natural sunlight, nearly 80 % of IDM was removed in 90 min irradiation. The heterojunction\u27s extensive intimate interfacial interactions amid LaTiO2N and g-C3N4 reduce the shortcomings of the two for a better photo-activity. The high visible activity, diminished recombination, high charge transfer is attributed to effective Z-scheme transfer facilitated by Fe3O4 nanoparticles. Scavenging experiments prove the importance of superoxide radicals as the dominant species responsible for photodegradation reaction. By mass spectrometry and total organic carbon analysis, a reaction mechanism was also reasonably proposed. The photocatalytic mechanism was discussed in light of conventional and Z-scheme transfer for better insight. The catalyst is stable, recyclable and magnetically separable. This investigation offers a new perspective in the rational design and manufacture of organic-inorganic nitrides based magnetically recoverable heterojunctions as LaTiO2N/g-C3N4@Fe3O4. Such heterojunctions present a new class of robust hierarchical photocatalytic materials which are capable of remediation of pharmaceutical residues under practical conditions

Designing of bentonite based nanocomposite hydrogel for the adsorptive removal and controlled release of ampicillin

© 2020 In pharmacy, semisynthetic antibiotics with beta-lactam ring are the most prominently used drugs. The use of these drugs for humans and animals is continuously expanding. Their presence in the water system even at low concentrations can prove to be fatal to living beings. Also, they can even grow antibiotic-resistant bacteria and thus elimination of such drugs becomes very essential. Our study is focused on batch experiments for adsorptive removal of ampicillin (AMP) and its cumulative release in different solutions using xanthan gum-cl-poly(itaconic acid)/bentonite (XG-cl-poly(IA)/BN) nanocomposite hydrogel. It was synthesized by facile microwave method. The adsorption data of AMP was analyzed using various isotherm models such as Langmuir, Freundlich, Temkin and kinetic models such as Pseudo-first order, Pseudo-second order and Intraparticle diffusion. The maximum adsorption capacity as determined from Langmuir model was 245.09 mg/g at 318 K and solution pH 7. Also, XG-cl-poly(IA)/BN nanocomposite hydrogel was evaluated for AMP release in distilled water and at different pH solutions (2.2, 5.4, 7.4 and 9.4). The maximum AMP release was observed at pH 2.2 (37%)

Preparation of highly porous nitrogen-doped biochar derived from birch tree wastes with superior dye removal performance

Heteroatom doping is a highly effective strategy that can be used to modify carbonaceous adsorbents to improve their chemical reactivity and increase their adsorptive properties. Herein, a simple method is reported for the preparation of nitrogen-doped biochar using a natural and abundant biowaste from birch trees and melamine as a nitrogen dopant for the adsorption of Acid red 18 (AR-18) dye from water. The doped biochars were also characterized for their performance during the treatment of synthetic effluents. The physicochemical characterization results showed that the N-doping process provoked remarkable chances on the biochar morphology, pore structure, and surface functionalities. N-doped biochar showed abundant nitrogen functional groups with 5.4 % of N in its structure while non-doped carbon showed traces with 0.47 %. Moreover, the specific surface area of doped biochar was dominated by mesopores (86.4 %) while non-doped was dominated by micropores (67.8 %). Raman analysis showed that the incorporation of N created more defects in the biochar structure. The adsorption experiments showed that the N-doping boosted the biochar adsorptive performance. The maximum adsorption capacity of the doped biochar was 545.2 mg g−1, while the non-doped exhibited 444.5 mg g−1, i.e., an increase of 22.6 %. The kinetic and equilibrium studies showed that Avrami fractional order and Liu models were the most suitable for describing the experimental AR-18 dye adsorption data. The equilibrium parameters were found to obey a nonlinear relationship with the temperature. Since the biochars are highly porous, pore filling was the main adsorption mechanism, however; AR-18 dye removal suggests that interactions such as electrostatic, hydrogen bonds, Lewis acid-base, and π-π between the adsorbent and the dye are involved. The thermodynamic studies showed that the removal of the AR-18 dye from the solution is dependent on temperature, exothermic, and spontaneous. The N-doped biochar showed excellent removal performances of contaminants from synthetic effluents confirming their high efficiency for color removal. This research shows that N-doping is an efficient strategy to design effective, low-cost, and sustainable adsorbents to remediate dye contamination in wastewater

Construction of dual Z-scheme g-C3N4/Bi4Ti3O12/Bi4O5I2 heterojunction for visible and solar powered coupled photocatalytic antibiotic degradation and hydrogen production: Boosting via I−/I3− and Bi3+/Bi5+ redox mediators

© 2020 Elsevier B.V. Inspired by waste to energy production, we report construction of dual Z-scheme advanced photocatalyst g-C3N4/Bi4Ti3O12/Bi4O5I2 heterojunction for coupled photocatalytic H2 evolution and degradation of antibiotics with high efficiency. The optimal CTBT-30 i.e (40 %g-C3N4/Bi4Ti3O12)/30 % Bi4O5I2 photocatalyst exhibited an excellent rate of H2 production under visible light (56.2 mmol g−1 h−1) along with simultaneous 87.1 % ofloxacin (OFL) removal. The H2 production rate is manifolds higher than in ultrapure water, sulfadiazine, rhodamine B and higher in hole scavenging triethanolamine. The interfacial intimate coupling with well-matched energy bands, foster the charge separation with effective Z-scheme transfer facilitated by I3−/I− and Bi3+/Bi5+ and redox mediators. The scavenging of majority of holes for direct oxidation or via [rad]OH radical formation leaves photogenerated electrons (at CB of g-C3N4 and Bi4O5I2) free for H2 evolution from H2O. Such work is promising for designing high photo-absorbing heterojunction photocatalysts for dual functionalities of clean energy production and environmental detoxification

Silicate glass matrix@Cu\u3csub\u3e2\u3c/sub\u3eO/Cu\u3csub\u3e2\u3c/sub\u3eV\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e7\u3c/sub\u3e p-n heterojunction for enhanced visible light photo-degradation of sulfamethoxazole: High charge separation and interfacial transfer

© 2020 Elsevier B.V. Focusing on the treatment of pharmaceuticals contaminated water by advanced oxidation processes, a novel three dimensional silicate glass matrix (3-DG) coupled Cu2O/Cu2V2O7 p-n heterojunction was constructed by in-situ hydrothermal technique. The optimal Cu2O/Cu2V2O7 with 30 wt % Cu2V2O7 (CV-30) degrades 90.1 % sulfamethoxazole (SMX) in 60 min and nearly 100 % removal in 45 min via coupling with 3-DG. Under natural sunlight ∼ 80 % SMX removal was observed. The internal electric field of the p-n junction facilitates the electron flow via the interface. 3-D silicate glass increases the visible light absorption dramatically via internal reflection which facilitates higher exposure for the junction and shortens the diffusion length of charge carriers. The effect of reaction parameters suggests that HCO3− and CO32− ions substantially escalate the SMX removal rate. Scavenging experiments and ESR probe suggest [rad]O2− as the main active species followed by [rad]OH radicals. The degradation products were detected by LC–MS analysis and a degradation mechanism was also predicted. The photocatalytic mechanism was explained in terms of the electron transfer facilitated by conventional transfer and Z-scheme. This strategy to construct such highly visible and solar active p-n heterojunctions will pave way for future opportunities for the degradation of recalcitrant pharmaceutical pollutants

Adsorption of omeprazole on biobased adsorbents doped with Si/Mg: kinetic, equilibrium, and thermodynamic studies

This paper proposes an easy and sustainable method to prepare high-sorption capacity biobased adsorbents from wood waste. A biomass wood waste (spruce bark) was employed to fabricate a composite doped with Si and Mg and applied to adsorb an emerging contaminant (Omeprezole) from aqueous solutions, as well as synthetic effluents loaded with several emerging contaminants. The effects of Si and Mg doping on the biobased material’s physicochemical properties and adsorptive performance were evaluated. Si and Mg did not influence the specific surface area values but impacted the presence of the higher number of mesopores. The kinetic and equilibrium data presented the best fitness by the Avrami Fractional order (AFO) and Liu isotherm models, respectively. The values of Qmax ranged from 72.70 to 110.2 mg g−1 (BP) and from 107.6 to 249.0 mg g−1 (BTM). The kinetic was faster for Si/Mg-doped carbon adsorbent, possibly due to different chemical features provoked by the doping process. The thermodynamic data showed that the adsorption of OME on biobased adsorbents was spontaneous and favorable at four studied temperatures (283, 293, 298, 303, 308, 313, and 318 K), with the magnitude of the adsorption correspondent to a physical adsorption process (ΔH° −1). The adsorbents were applied to treat synthetic hospital effluents and exhibited a high percentage of removal (up to 62%). The results of this work show that the composite between spruce bark biomass and Si/Mg was an efficient adsorbent for OME removal. Therefore, this study can help open new strategies for developing sustainable and effective adsorbents to tackle water pollution