Remediation Of Contaminated Water Research Articles

Conjugated polymers decorated lignocellulosic nanocomposites for malachite green contaminated water remediation

Various novel conjugated polymer composites were synthesized via in situ chemical oxidative polymerization on lignocellulosic waste, notably Azadirachta indica sawdust. The composites, including Azadirachta indica/polyindole (AIS/PIn), Azadirachta indica/polyaniline (AIS/PAn), Azadirachta indica/polythiophene (AIS/PTh), and Azadirachta indica/polypyrrole (AIS/PPy), were investigated for their porous structure, ease of synthesis, unique adsorptive properties, and adjustable morphology. The synthesized composites were characterized using SEM/EDS, TEM/SAED, XRD, BET, TGA, and FTIR, revealing detailed insights into their structural and morphological features. The potential of these composites as efficient adsorbents for removing malachite green (MG) dye from water was a vital focus of this research. Batch experiments were conducted to assess the impact of various factors on adsorption, such as adsorbent/adsorbate contact time (0–280 min.), adsorbent dosage (0.4–20.0 g/L), initial adsorbate concentration (25–100 ppm), pH (2–13), and temperature (30–60 °C). The results indicate a remarkable removal efficiency of 89.98 % for MG with an initial concentration (Co) of 50 mg/L, achieved within 120 min using 0.4 g/L of AIS/PIn at a pH above 8.3. The Langmuir adsorption isotherm model provided the best fit for the experimental data, with maximum adsorption capacities of 384.61 mg g−1 for AIS/PIn, 344.82 mg g−1 for AIS/PAn, 277.77 mg g−1 for AIS/PTh, and 256.41 mg g−1 for AIS/PPy. This suggests monolayer adsorption. The adsorption kinetics conformed to a pseudo-second-order model, with the process being endothermic, feasible, and associated with positive entropy, thereby underlining its favorability and spontaneity. The desorption studies determined that 0.1 M HCl was the most effective desorbing agent compared to NaOH, NaCl, CH3COOH, and H2O. The spectral and effect of pH analyses suggested that the adsorption mechanisms might involve multiple interactions, prominently including electrostatic interactions, hydrogen bonding, π-π interactions, and n-π interactions. Based on the findings, it is submitted that the conjugated polymer decorated biomass composite adsorbents exhibit reasonable recyclability over multiple cycles, versatility, and potent efficacy as low-cost adsorbents for eliminating MG dye from aqueous systems.

Implementation of visible light-driven photocatalytic degradation of antibiotic chloramphenicol using Bi2S3/ZrO2 and Bi2WO6/ZrO2 heteronanostructures

Zirconium dioxide-incorporated bismuth sulfide (Bi2S3/ZrO2) and bismuth tungstate (Bi2WO6/ZrO2) heteronanostructures (HNSs) were fabricated to serve as photocatalysts for the visible light-driven degradation of antibiotic chloramphenicol (CAP). A two-step hydrothermal process was applied to synthesize HNSs, and their structural and optical properties were validated by several analytical techniques. Interestingly, a multi-structural feature was ascertained in which nanoflower-structured ZrO2 was attached to the surface of nanorod- and nanosheet-structured Bi2S3 and Bi2WO6, respectively, resulting in the formation of Bi2S3/ZrO2 and Bi2WO6/ZrO2 HNSs. For the photocatalytic degradation of CAP, both HNSs showed magnificent catalytic activity during a visible light-based photocatalytic degradation. Furthermore, when peroxymonosulfate (PMS) was used as an activator for an oxidative catalytic reaction, the photocatalytic degradation rate was drastically enhanced to nearly 5 times. Bi2S3/ZrO2 and Bi2WO6/ZrO2 showed ∼96 % CAP degradation in 15 min, with rate constants of 0.2511 and 0.2163 min−1, respectively. The synergistic effects of the substantial generation and separation of photoinduced charge carriers are responsible for the highly improved catalytic activity. Scavenger analysis demonstrated that hydroxyl radical species predominated in the effective degradation process. These kinds of inorganic-based HNSs are expected to rule the field of contaminated water remediation, which will also expand a platform for the fabrication of photocatalyst materials.

Cobalt oxide coupled with graphitic carbon nitride composite heterojunction for efficient Z-scheme photocatalytic environmental pollutants degradation performance

The Co3O4/g-C3N4 Z-scheme composite heterojunction has been effectively built in a facile sonication-assisted hydrothermal manner. The as-synthesized optimal 0.2 M Co3O4/g-C3N4 (GCO2) composite photocatalysts (PCs) revealed admirable degradation efficiency towards methyl orange (MO, 65.1%) and methylene blue (MB, 87.9%) organic pollutant compared with bare g-C3N4 within 210 min under light irradiation. Besides, the features of investigating structural, morphological and optical properties have evidence that the unique decoration effect of Co3O4 nanoparticles (NPs) on the g-C3N4 structure with intimate interface heterojunction of well-matched band structures noticeably facilitates the photo-generated charge transport/separation efficiency, reduces the recombination rates and widens the visible-light fascination which could advantageous to upgrading photocatalytic action with superior redox ability. Especially, the probable Z-scheme photocatalytic mechanism pathway is also elucidated in detail based on the quenching results. Hence, this work delivers a facile and hopeful candidate for contaminated water remediation via visible-light photocatalysis over the efficient g–C3N4–based catalysts.

Fe3+-cysteine enhanced persulfate fenton-like process for quinclorac degradation: A wide pH tolerance and reaction mechanism

A green, high-efficiency, and wide pH tolerance water remediation process has been urgently acquired for the increasingly exacerbating contaminated water. In this study, a Fe3+/persulfate (Fe3+/PS) system was employed and enhanced with a green natural ligand cysteine (Cys) for the degradation of quinclorac (QNC). The introduction of Cys into the Fe3+/PS system widened the effective pH range to 9 with a superior removal rate for QNC. The mechanism revealed that the Fe3+/Cys/PS system can enhance the ability of degrading QNC by accelerating the Fe3+/Fe2+ redox cycle, maintaining Fe2+ concentration and thereby generating more HO• and SO4•–. The impact factors (i.e., pH, concentrations of PS, Fe3+ and Cys) were optimized as well. This work provides a promising strategy with high catalytic activity and wide pH tolerance for organic contaminated water remediation.

A Review of Manganese-Oxidizing Bacteria (MnOB): Applications, Future Concerns, and Challenges.

Groundwater serving as a drinking water resource usually contains manganese ions (Mn2+) that exceed drinking standards. Based on the Mn biogeochemical cycle at the hydrosphere scale, bioprocesses consisting of aeration, biofiltration, and disinfection are well known as a cost-effective and environmentally friendly ecotechnology for removing Mn2+. The design of aeration and biofiltration units, which are critical components, is significantly influenced by coexisting iron and ammonia in groundwater; however, there is no unified standard for optimizing bioprocess operation. In addition to the groundwater purification, it was also found that manganese-oxidizing bacteria (MnOB)-derived biogenic Mn oxides (bioMnOx), a by-product, have a low crystallinity and a relatively high specific surface area; the MnOB supplied with Mn2+ can be developed for contaminated water remediation. As a result, according to previous studies, this paper summarized and provided operational suggestions for the removal of Mn2+ from groundwater. This review also anticipated challenges and future concerns, as well as opportunities for bioMnOx applications. These could improve our understanding of the MnOB group and its practical applications.

Polyethylenimine-grafted nitrogen-doping magnetic biochar for efficient Cr(VI) decontamination: Insights into synthesis and adsorption mechanisms

Herein, polyethylenimine (PEI)-grafted nitrogen (N)-doping magnetic biochar (PEIMW@MNBCBM) was synthesized, and characterization results showed that the microwave-assisted PEI grafting and ball milling-assisted N doping introduced abundant amino, pyridine N and pyrrole N structures onto biochar, which possessed high affinity to Cr(VI) in the anion form. The as-prepared PEIMW@MNBCBM displayed pH-dependence adsorption performance and high tolerance to co-existing ions with maximum uptake capacity of Cr(VI) identified as 183.02 mg/g. Furthermore, PEIMW@MNBCBM could bind Cr(VI) through electrostatic attraction, complexion, precipitation, reduction and pore filling. Especially, effective reduction of Cr(VI) was ascribed to cooperative electron transfer of partial oxygen-containing functional groups, intramolecular pyridine/pyrrole N, protonated amino and Fe2+ on the adsorbent, while oxygen-containing and amino functional groups from N-doping biochar and PEI synergistically complexed Cr(III) via providing lone pair electrons to form coordinate bonds. Furthermore, the stable precipitation was formed between Fe3+ and Cr(III). Additionally, the Cr(VI) elimination efficiency could maintain 95.83% even after four adsorption-desorption cycles, suggesting PEIMW@MNBCBM as a high-performance adsorbent for Cr(VI) contaminated water remediation.

Fe-C-based materials: synthesis modulation for the remediation of environmental pollutants-a review.

Presently, the rapid pace in the discovery of emerging aquatic pollutants is increasing the demand for the remediation and treatment of our natural resources. Regarding this, nanotechnology is being considered the potential solution for contaminated water remediation with techniques such as filtration, adsorption, catalysis, and desalination. For this purpose, zerovalent iron (ZVI) is being widely used in the remediation of environmental pollutants due to its large specific surface area and high reactivity. However, ZVI is easy to agglomerate and oxidize, limiting its application in the real environment. Therefore, the present study was designed to discuss the preparation and characterization methods of ZVI composite materials, factors affecting adsorption, the removal effect, and adsorption mechanism of different pollutants by Fe-C materials because the optimization and modification of nano-zero-valent iron is a hot research topic nowadays in this field. Moreover, this paper does also analyze the possibility of the practical application prospects of the team's technology for preparing iron-carbon materials. Thus, this information will be helpful for the development and application of Fe-C-based technologies for water and soil remediation and the prediction of the future research direction of Fe-C composite materials.

Nanoscale zero-valent iron/silver@activated carbon-reduced graphene oxide: Efficient removal of trihalomethanes from drinking water

AC-supported nanoscale zero-valent iron composites (nZVI/AC) exhibit significant environmental implications for trihalomethanes (THMs)-contaminated water remediation. To improve the adsorption and degradation capability of AC, herein, a composite (nZVI/Ag@AC-RGO) consisting of AC, reduced graphene oxide (RGO), nanoscale zero-valent iron (nZVI), and silver (Ag) was synthesized and characterized using several techniques, such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption-desorption isotherms, and X-ray photoelectron spectroscopy (XPS). The analysis of textural and morphological structures showed that a tightly-attached RGO film, amorphous iron, and weak crystal silver nanoparticles with a size of 20–30 nm were evenly immobilized on the support. Specific surface area increased by 19.12% after supporting RGO, while it decreased after supporting nZVI and Ag due to the partial blockage of micropores. The Fe surface was concurrently coated by iron oxides (Fe2O3, FeOOH) and Ag. THMs were eliminated through multilayer reaction processes. The values of the adsorption constant (KF) of chloroform (CHCl3), dichlorobromoethane (CHBrCl2), dibromochloroethane (CHBr2Cl), and tribromomethane (CHBr3) adsorbed by nZVI/Ag@AC-RGO increased by 34.4, 33.7, 81.6, and 67.3%, respectively, compared to pristine AC. THMs with more Br atoms exhibited better removal efficiency and adsorption capacity, along with a higher oxidation degree of the Fe surface. CHBrCl2 and CHBr2Cl mainly decomposed into chloromethane (CH3Cl) and dichloromethane (CH2Cl2), and CHBr3 and CHCl3 primarily degraded into dibromomethane (CH2Br2) and CH2Cl2, respectively, along with generating Cl− and Br−. Conclusively, THMs-contaminated water could be remediated by coupling AC pre-enrichment and the reactivity of nZVI/Ag.

On the Versatile Role of Electrospun Polymer Nanofibers as Photocatalytic Hybrid Materials Applied to Contaminated Water Remediation: A Brief Review.

A wide variety of materials, strategies, and methods have been proposed to face the challenge of wastewater pollution. The most innovative and promising approaches include the hybrid materials made of polymeric nanofibers and photocatalytic nanoparticles. Electrospun nanofibers with unique properties, such as nanosized diameter, large specific surface area, and high aspect ratio, represent promising materials to support and stabilize photocatalytic nanosized semiconductors. Additionally, the role performed by polymer nanofibers can be extended even further since they can act as an active medium for the in situ synthesis of photocatalytic metal nanoparticles or contribute to pollutant adsorption, facilitating their approach to the photocatalytic sites and their subsequent photodegradation. In this paper, we review the state of the art of electrospun polymer/semiconductor hybrid nanofibers possessing photocatalytic activity and used for the remediation of polluted water by light-driven processes (i.e., based on photocatalytic activity). The crucial role of polymer nanofibers and their versatility in these types of procedures are emphasized.

Synthesis and characterization of poly(styrene-co-divinylbenzene) and nanomagnetite structures

The use of iron oxide nanoparticles for the synthesis of adsorbents materials with application in contaminated water remediation is based on both their magnetic and adsorption properties. Poly(styrene-co-divinylbenzene) - Poly(Sty-co-DVB)microparticles are widely known for this use and the addition of magnetite comes to add magnetic properties, however it should not limit the functionalization processes for formation of cationic and/or anionic resins. Thus, there is a concern about the stability of magnetite in acidic environments, as required by the sulfonation process, for example. Furthermore, the synthesis of composites with magnetic nanoparticles is a challenge due to the strong magnetic dipole interactions between particles resulting from the high specific surface area, making them susceptible to aggregation. As well as oxidation during the synthesis process can compromise the structure of the initial magnetic material. In this sense, the present work validated processes for the synthesis of Poly(Sty-co-DVB)/magnetite microparticles that sought, as a final result, the incorporation of magnetite aiming to preserve its initial structural conformation. Thus, started from original synthesis method aimed at the production of Poly(Sty-co-DVB) microparticles without magnetite, to methods in which magnetite nanoparticles is added through two distinct processes, different regarding the use or not of oleic acid in its preparation.In this method article we show:•Combination of methods to preserve the structure of magnetite in the Poly(Sty-co-DVB)/magnetite composite.•Simple method of adding magnetite to the Poly(Sty-co-DVB)/magnetite composite synthesis process.•Magnetite treatment method with oleic acid in Poly(Sty-co-DVB)/magnetite composite synthesis.The samples were characterized using Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Mössbauer spectroscopy to evaluate the chemical modifications that were introduced in the original synthesis method.

Investigations on amidoxime grafted sepiolite based chitosan organic–inorganic nanohybrid composite beads towards wastewater detoxification

This work explores the fabrication of organic–inorganic nanohybrid based biopolymer composite systems for the cleaning of different contaminants from wastewater. This system involves the simultaneous radiation grafting techniques for sepiolite (SP) modification and the simple mixing of modified-SP with biopolymer matrix, chitosan (CS). The SP beads were chemically modified with amidoxime prior to its use in composite systems. The synthesized composite beads were characterized using scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), nitrogen physical adsorption (BET) investigations, Fourier transform infrared (FT-IR), atomic absorption and UV–visible spectroscopy. Hydrolytic stability of beads was also investigated in aqueous media, beads showed excellent stability in aqueous medium and in acidic environment. Here, the sorption profile of copper over amidoxime grafted SP-nanohybrid (MSP) incorporating CS-beads is reported. Furthermore, the key adsorptive variables, i.e. contact time, adsorbent dose, and concentration of adsorbate are discussed. Different isothermal (Langmuir and Freundlich) and kinetics model were also elaborated. Langmuir isotherm and pseudo-second-order models are proved to be the best fit models for Cu (II) removal in aqueous system. To explore the efficacy of the material towards organic pollutants, methylene blue (MB) was selected as model compound and adsorbed on nanohybrid beads. The results revealed that organic–inorganic nanohybrid incorporating CS beads are quite effective for contaminated water remediation, owing to their better adsorptive performance, high stability and easy application.

Porous g-C3N4 and α-FeOOH bridged by carbon dots as synergetic visible-light-driven photo-fenton catalysts for contaminated water remediation

Merging photocatalysis with Fenton-like reaction provides a promising synergetic advanced oxidation technology for water treatment, whereas the rational design of efficient cooperative photo-Fenton system still remains a great challenge. In this study, a ternary α-FeOOH/carbon dots/porous g-C3N4 (α-FeOOH/CDs/p-GCN) composite is developed as visible-light-driven heterogeneous photo-Fenton catalyst for contaminated water remediation. α-FeOOH nanorods are in-situ grown on porous g-C3N4 substrates, among which CDs are intercalated as high-speed electron transmission bridges, simultaneously preventing the photogenerated electron-hole recombination and accelerating the Fe3+/Fe2+ redox cycle. The distinctive heterostructure and synergetic catalytic effect endow α-FeOOH/CDs/p-GCN with superior efficiency, reusability, and universality for recalcitrant pollutant elimination, the reaction rate of which is nearly 13.6, 7.3, 3.4, 1.4, and 5.1 times higher than that of α-FeOOH, bulk g-C3N4 (b-GCN), p-GCN, α-FeOOH/p-GCN, and α-FeOOH/CDs/b-GCN, respectively. The FeOOH/CDs/p-GCN also demonstrates excellent tolerance to realistic environmental matrices including deionized water, sea water, river water, wastewater, and underground water. HO• and •O2− radicals are proved to be the predominant contributors in the photo-Fenton system. This work provides an efficient synergetic visible-light-driven photo-Fenton catalyst possessing great potential for practical contaminated water remediation.

Assessment of the phytoremediation capabilities of bracken fern (Pteridium aquilinum) for the remediation of heavy metals (Pb, Ni and Cd) contaminated water

This study was carried out to investigate the potential uptake of heavy metals (Pb, Ni, and Cd) by Pteridium aquilinum plant from aqueous solutions. The whole plant strands were cultured in 36 experimental pots containing 5, 10 and 15 (mg/L) of Pb2+, Ni2+ and Cd2+ aqueous solutions. The plants were harvested after 24, 48, 72 and 96 hours of exposure and segmented into leaves, stem and root, respectively. The heavy metals content in the plant parts were analyzed using Atomic Absorption Spectrophotometer version VGP 210. The highest actual accumulations for Pb, Ni and Cd were recorded in the root at 15 mg/L of the aqueous solution after 96 hours of exposure with mean values of 4.29±0.04, 4.06±0.01 and 0.65±0.00 mg/kg, respectively. The highest total actual accumulations recorded in the plant were 9.19±0.14, 10.80±0.03, and 1.23±0.04 mg/kg for Pb, Ni and Cd, respectively. The accumulation of the heavy metals in the plant parts was in this order; root > stem > leaves. The results reveal that, the accumulation of heavy metals in the plant increases with increase in the concentration of the aqueous solutions and the duration of exposure to the aqueous solutions. The uptake of heavy metals by the plant is in this order; Ni > Pb > Cd. The translocation factor (TF) recorded for Pb, Ni and Cd in the plant were all greater than 1 (>1) except for Cd at exposure duration of 96 h in the 15 mg/L Cd2+ aqueous solutions, with the highest TF values of 2.500, 1.886 and 1.601, respectively. This indicates that more of the heavy metals were stored in the shoot. P. aquilinum is therefore described as a good accumulator plant, which could be used for phytoextraction of Pb, Ni and Cd in aqueous solutions of the metals. Key words: Phytoremediation, Pteridium aquilinum, heavy metals, contamination, translocation factor.

Hierarchically porous covalent organic framework for adsorption and removal of triphenylmethane dyes

Triphenylmethane (TPM) dyes as one of common organic pollutants have been severely criticized while it comes to their negative effects on the environment and human beings. In this study, using 1,3,5-triformylbenzene (Tb) and benzidine (Bd) as building blocks, we fabricated a hierarchically porous covalent organic framework foam (TbBd-foam) via a simple yet accomplished gas-foaming technique to adsorb and remove two typical TPM dyes malachite green (MG) and crystal violet (CV) from aqueous solution. Attributed to the use of baking soda, CO2 effervesced continuously during the crystallization of TbBd-foam, and thereby creating disordered porous system which can quicken the diffusion of MG and CV through the pore network in TbBd-foam. Benefit from this merit, the adsorption equilibrium of MG and CV can reach only with 30 min, and the maximum adsorption capacity of TbBd-foam for MG and CV was calculated to be 172.4 mg g−1 and 149.3 mg g−1, respectively. More fascinatingly, TbBd-foam can be facilely recycled upon the treatment with ethanol solution containing HCl (0.1%). Taken together, TbBd-foam might be a potential adsorbent for high-performance contaminated water remediation.

Remediation of nitrate contamination by membrane hydrogenotrophic denitrifying biofilm integrated in microbial electrolysis cell

Complete biological denitrification is usually restricted in electron donor lacking waters. Hydrogenotrophic denitrification attracts attention for its clean and cost-efficiency advantages. Therein, the hydrogen could be effectively generated by microbial electrolysis cells (MECs) from organic wastes. In this study, a gas diffusion membrane (GDM) integrated MEC (MMEC) was constructed and provided a novel non-polluting approach for nitrate contaminated water remediation, in which the hydrogen was recovered from substrate degradation in anode and diffused across GDM as electron donor for denitrification. The high overall nitrogen removal of 91 ± 0.1%–95 ± 1.9% and 90 ± 1.6%–94 ± 2.2% were respectively achieved in Ti-MMEC and SS-MMEC with titanium and stainless-steel mesh as cathode at all applied voltages (0.4–0.8 V). Decreasing applied voltage from 0.8 to 0.4 V significantly improved the electron utilization efficiency for denitrification from 26 ± 3.6% to 73 ± 0.1% in Ti-MMEC. Integrating MEC with GDM greatly improved TN removal by 40% under applied voltage of 0.8 V. The hydrogenotrophic denitrifiers of Rhodocyclaceae, Paracoccus, and Dethiobacter, dominated in MMECs facilitating TN removal. Functional denitrification related genes including napAB, nirKS, norBC and nosZ predicted by PICRUSt2 based on 16S rRNA gene data demonstrated higher abundance in MMECs.

Perspectives regarding metal/mineral-incorporating materials for water purification: with special focus on Cr(vi) removal

Metal/mineral-incorporating materials for toxic Cr(vi) removal.

Surface-bound radical control rapid organic contaminant degradation through peroxymonosulfate activation by reduced Fe-bearing smectite clays

Heterogeneously activated peroxymonosulfate (PMS)-based advanced oxidation technologies (AOTs) have received increasing attention in contaminated water remediation. However, PMS activation by reduced clay minerals (e.g., reduced Fe-bearing smectite clays) has rarely been explored. Herein, PMS decomposition by reduced Fe-bearing smectite clays was investigated, and the hydroxyl radical (OH) and sulfate radical (SO4−) formation mechanisms were elucidated. Reduced nontronite NAu-2 (R-NAu-2) activated PMS efficiently to induce rapid degradation of diethyl phthalate (DEP) within 30 s. Mössbauer spectroscopy, FTIR and XPS analyses substantiated that distorted trans-coordinated Fe(II)Fe(II)Fe(II)OH entities were mainly responsible for rapid electron transfer to regenerate clay surface Fe(II) for PMS activation. Chemical probe, radical quenching, and electron paramagnetic resonance (EPR) results confirmed that OH and SO4− were mainly bound to the clay surface rather than in bulk solution, which resulted in the rapid degradation of organic compounds such as DEP, sulfamethoxazole, phenol, chlortetracycline and benzoic acid. Anions such as Cl− and NO3− had a limited effect on DEP degradation, while HCO3− inhibited the DEP degradation due to the increase of reaction pH. This study provides a new PMS activation strategy using reduced Fe-bearing smectite clays that will contribute to rapid degradation of organic contaminants using PMS-based AOTs.

Polyaniline coated nickel oxide nanoparticles for the removal of phenolic compounds: Equilibrium, kinetics and thermodynamic studies

Nanocomposites of transition metal oxides with polymeric fabrication have gained much interest as adsorbents for contaminated water remediation. Here, nickel oxide-polyaniline (NiO-PANI) nanocomposite was synthesized and has been employed as adsorbent for organic pollutants like p-nitrophenol and resorcinol in water. The structural, surface and thermal properties of the prepared adsorbents has been studied by using Fourier-transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD), thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). Batch adsorption experiments were performed to study the effect of contact time, initial adsorbate concentration, adsorbent amount, solution pH and temperature on the adsorption of resorcinol and p-nitrophenol. The adsorption process follows pseudo-second order kinetics suggesting chemical interaction between the adsorbent and the adsorbate. Equilibrium studies showed that the adsorption process is best fitted with Temkin isotherm model for resorcinol while for p-nitrophenol Freundlich isotherm model gives the best fit. The maximum Langmuir adsorption capacity for resorcinol and p-nitrophenol has been found to be 19.53 mg/g and 29.78 mg/g respectively at 303 K. Thermodynamic studies showed the adsorption process to be endothermic, spontaneous and entropically driven. The reusability study of the adsorbent has been performed upto four cycles which shows that the adsorbent can be regenerated and reused. The results of this work show that the polyaniline (PANI) fabricated nickel oxide (NiO) nanoparticles effectively adsorbs resorcinol and p-nitrophenol from aqueous medium. This paves the way for its use in environmental remediation.

Facile assembled biochar-based nanocomposite with improved graphitization for efficient photocatalytic activity driven by visible light

The preparation processes of efficient photocatalyst containing defect regulation and heterostructure construction are usually complicated and difficult to control at present, besides, the catalyst agglomeration in solution further limits their application. There is an urgent need for designing a potentially cheap, efficient, sustainable and easy-prepared nanocomposite to improve photocatalytic performance. In present study, the facile synthesized porous graphitic carbon with microtubular structure, high graphitization degree and abundant porosity demonstrates an outstanding advantage of excellent conductivity and facilitated mass transport. Such porous graphite biochar (PGBC) self-assembled with g-MoS2 nanosheets is observed by the optimized band gap, enhanced visible light harvesting, accelerated charge transfer and efficient photo-generated carrier’s separation. Considering the favorable specific surface area and pore distribution of PGBC for avoiding nanosheet agglomeration, the as-prepared composites display quite high efficiency for tetracycline hydrochloride (TC) removal based on the synergistic action of the desirable absorption and photocatalytic capability. Mechanism exploration indicates that surface adsorption is mainly dominated by electrostatic interaction, hydrogen bonding, π-π stacking and pore-filling, and hole (h+) and hydroxyl radical (·OH) are the predominant active species responsible for TC degradation. Furthermore, the nanocomposites possess advisable stability performance for TC removal in contaminated river water, further providing an underlying insight for establishing high-efficient and easy-prepared photocatalysts in practical contaminated water remediation.

Hydrocarbon contaminated water remediation using a locally constructed multi-stage bioreactor incorporated with media filtration

The present study investigated the coupling effect of biodegradation and media filtration in treating hydrocarbon contaminated water. The study recorded reductions in total petroleum hydrocarbon, total dissolved solids, turbidity and microbial load. The study was essentially a simulated pump and treat process that involved the pumping of hydrocarbon contaminated water for treatment in a locally designed multi-stage bioreactor incorporated with media filtration. A mixed consortium of hydrocarbon-eating microbes was applied in the study. Hydrocarbon-eating microbes were isolated from hydrocarbon contaminated soils obtained from selected mechanic workshops. Bamboo chips and coconut husk chips were applied as support media for microbial attachment within the bioreactor compartment of the treatment setup. Applied support media were approximately 2-4 cm in size. Media filters applied comprised three locally manufactured candle filters two of which were respectively impregnated with granular activated charcoal and sand. The coupling effect of biodegradation and media filtration recorded over 99 % (> 8.7 mg/L) total petroleum hydrocarbon removal. Microbial load reduction ranged from 3.57±0.11E+20 to 7.45±0.26E+20 Colony forming unit/mL, total dissolved solids reduction from 30.00±5.66 to 131.00±0.00 mg/L and turbidity reduction from 39.00±1.41 to 123.50±0.71 nephelometric turbidity units. Biodegradation accounted for 69.70±0.63 and 90.72±2.36 % total petroleum hydrocarbon removal respectively for bamboo chips and coconut husk chips.