At present, heavy metal pollution is a major environmental concern and the adsorption technique is a potent method for removal of these heavy metals from wastewater. Activated carbon is one of the best adsorbents for metal ionsremoval but it is sometimes restricted due to high cost and problems with regeneration hamper large scale application. Low cost adsorbent is alternatively being introduced to replace activated carbon since it is available in large quantity, renewable and inexpensive. Hence, Pennisetum purpureum(elephant grass) was investigated for its potential in cadmium ions removal. The adsorbent was characterized by Fourier Transforms Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) analyses.The effects of pH (1 to 5), initial metal ion concentration (5 to 25 mg/L), contact time (10 to 60 minutes) and adsorbent dosage (0.2 to 1.0 g) on cadmium ions removal were conducted by batch adsorption experiments. In this study, the FT-IR results demonstrated that the functional groups for untreated and nitric acid-treated P. purpureum mainly consisted of carbonyl, carboxyl, hydroxyl and amine groups which are able to bind with positively charged cadmium ions. SEM micrographs have proven that nitric acid modification would remove the surface impurities of P. purpureum, which increased the surface roughness, produced deep, open pores and better pore size distribution. From the BET and BJH analyses, the treated P. purpureum was mesoporous, had larger surface area and pore volume compared to untreated P. purpureum. The best pH, adsorbent dosage and contact time were pH 4, 0.6 g and 30 minutes, respectively. The highest removal percentage of cadmium ions for both untreated and treated P. purpureum were 92% and 98% correspondingly. The results shown strengthened the fact that both biosorbents have great potential in cadmium ions removal.
Wastewater is water that has already been contaminated by domestic, industrial and commercial activity that needs to be treated before it could be discharged into some other water bodies to avoid even more groundwater contamination supplies. It consists of various contaminants like heavy metals, organic pollutants, inorganic pollutants and Emerging contaminants. Research has been doing on all types of contaminates more than a decade, but this emerging contaminants is the contaminants which arises mostly from pharmaceuticals, personal care products, hormones and fertilizer industries. The majority of emerging contaminants did not have standardized guidelines, but may have adverse effects on human and marine organisms, even at smaller concentrations. Typically, extremely low doses of emerging contaminants are found in the marine environment and cause a potential risk to the aquatic animals living there. When contaminants emerge in the marine world, they are potentially toxic and pose many risks to the health of both man and livestock. The aim of this article is to review the Emerging contaminate sources, detection methods and treatment methods. The purpose of this study is to consider the adsorption as a beneficial treatment of emerging contaminants also advanced and cost effective emerging contaminates treatment methods.
Thriving oil palm agroindustry comes at a price of voluminous waste generation, with palm oil mill effluent (POME) as the most cumbersome waste due to its liquid state, high strength, and great discharge volume. In view of incompetent conventional ponding treatment, a voluminous number of publications on non-conventional POME treatments is filed in the Scopus database, mainly working on alternative or polishing POME treatments. In dearth of such comprehensive review, all the non-conventional POME treatments are rigorously reviewed in a conceptual and comparative manner. Herein, non-conventional POME treatments are sorted into the five major routes, viz. biological (bioconversions - aerobic/anaerobic biodegradation), physical (flotation & membrane filtration), chemical (Fenton oxidation), physicochemical (photooxidation, steam reforming, coagulation-flocculation, adsorption, & ultrasonication), and bioelectrochemical (microbial fuel cell) pathways. For aforementioned treatments, the constraints, pros, and cons are qualitatively and quantitatively (with compiled performance data) detailed to indicate their process maturity. Authors recommended (i) bioconversions, adsorption, and steam reforming as primary treatments, (ii) flotation and ultrasonication as pretreatments, (iii) Fenton oxidation, photooxidation, and membrane filtration as polishing treatments, and (iv) microbial fuel cell and coagulation-flocculation as pretreatment or polishing treatment. Life cycle assessments are required to evaluate the environmental, economic, and energy aspects of each process.
In recent times, research interest into the development of biodegradable, cost-effective and environmental friendly adsorbents with favourable properties for adsorption of pollutants is a challenge. Modification of chitosan via different physical and chemical methods have gained attention as a promising approach for removing organic (such as dyes and pharmaceuticals) and inorganic (such as metal/metal ions) pollutants from aqueous medium. In this regard, researchers have reported grafting and cross-linking approach among others as a potentially useful method for chitosan's modification for improved adsorption efficiency with respect to pollutant uptake. This article reviews the trend in chitosan modification, with regards to the summary of some recently published works on modification of chitosan and their adsorption application in pollutants (metal ion, dyes and pharmaceuticals) removal from aqueous medium. The review uniquely highlights some common cross-linkers and grafting procedures for chitosan modification, their influence on structure and adsorption capacity of modified-chitosan with respect to pollutants removal. Findings revealed that the performance of modified chitosan for adsorption of pollutants depends largely on the modification method adopted, materials used for the modification and adsorption experimental conditions. Cross-linking is commonly utilized for improving the chemical and mechanical stabilities of chitosan but usually decreases adsorption capacity of chitosan/modified-chitosan for adsorption of pollutants. However, literature survey revealed that adsorption capacity of cross-linked chitosan based materials have been enhanced in recently published works either by grafting, incorporation of solid adsorbents (e.g metals, clays and activated carbon) or combination of both prior to cross-linking.
Industrial effluents contain several organic and inorganic contaminants. Among others, dyes and heavy metals introduce a serious threat to drinking waterbodies. These pollutants can be noxious or carcinogenic in nature, and harmful to humans and different aquatic species. Therefore, it is of high importance to remove heavy metals and dyes to reduce their environmental toxicity. This has led to an extensive research for the development of novel materials and techniques for the removal of heavy metals and dyes. One route to the removal of these pollutants is the utilization of magnetic carbon nanotubes (CNT) as adsorbents. Magnetic carbon nanotubes hold remarkable properties such as surface-volume ratio, higher surface area, convenient separation methods, etc. The suitable characteristics of magnetic carbon nanotubes have led them to an extensive search for their utilization in water purification. Along with magnetic carbon nanotubes, the buckypaper (BP) membranes are also favorable due to their unique strength, high porosity, and adsorption capability. However, BP membranes are mostly used for salt removal from the aqueous phase and limited literature shows their applications for removal of heavy metals and dyes. This study focuses on the existence of heavy metal ions and dyes in the aquatic environment, and methods for their removal. Various fabrication approaches for the development of magnetic-CNTs and CNT-based BP membranes are also discussed. With the remarkable separation performance and ultra-high-water flux, magnetic-CNTs, and CNT-based BP membranes have a great potential to be the leading technologies for water treatment in future.
In this study, a series of copper-ion-doped titanium dioxide (Cu-ion-doped TiO₂) nanotubes (NTs) were synthesized via a hydrothermal method by the concentration variation of doped Cu ions (0.00, 0.50, 1.00, 2.50, and 5.00 mmol). In addition, the samples were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), nitrogen gas adsorption measurements, and ultraviolet-visible (UV-Vis) diffuse-reflectance spectroscopy. The photocatalytic activity of the Cu-iondoped TiO₂ NTs was investigated for the degradation of methyl orange (MO) under sunlight. The results obtained from the structural and morphological studies revealed that, at low concentrations of Cu-doped TiO₂ NTs, Cu is incorporated into the interstitial positions of the TiO₂ lattice, affording a new phase of TiO₂ (hexagonal) instead of the anatase TiO₂ (tetragonal) observed for undoped TiO₂ NTs. EDX analysis confirmed the presence of Cu in the TiO₂-based photocatalyst. All of the investigated samples exhibited a hollow fibrous-like structure, indicative of an NT morphology. The inner and outer diameters of the NTs were 4 nm and 10 nm, respectively. The photocatalysts exhibited a large surface area due to the NT morphology and a type IV isotherm and H3 hysteresis, corresponding to the mesopores and slit-shaped pores. The Cu-ion-doped TiO₂ NTs were excited by sunlight because of their low bandgap energy; and after the incorporation of Cu ions into the interstitial positions of the TiO₂ lattice, the NTs exhibited high visible-light activity owing to the low bandgap.
Ion-imprinting polymers (IIPs) materials draw the great recognition because of the powerful selectivity to the desired metal ions. Therefore, the ion-imprinting polymer (Ce-IIP) was prepared by using cerium metal with amidoxime ligand as the complexing agent, in addition ethylene glycol dimethacrylate (EGDMA) and 2,2-azobisisobutyronitrile (AIBN) are crosslinking agent and free radical initiator, respectively. Aqueous HCl was applied to leach the cerium ions from the imprinted polymer for the creation of cavities of template, which is utilized for further cerium ions adsorption with high selectivity. The Ce-IIP was characterized by using ICP-MS, FE-SEM and also solid state analysis by UV-vis NIR spectroscopy. FT-IR study confirmed the complexation of the Ce-IIP was successful. The optimum pH was found to be 6 and the highest adsorption capacity was estimated about 145 mg g-1. Thus, the prepared Ce-IIP gave very good selectivity to cerium ions in the presence of lanthanide ions and also Ce-IIP can be reused 10 times without a substantial loss in adsorption capacity.
The present work highlights the facile synthesis of hydrophobic palm fatty acid functionalized Fe3O4 nanoparticles (MNP-FA) for the efficient removal of oils from the surface of water. An intense hydrophobic layer was introduced on the surface of Fe3O4 nanoparticles functionalized by the palm fatty acid obtained from the hydrolysis of palm olein. Scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), Energy dispersive X-ray spectroscopy (EDX) and water contact angle analysis (WCA) measurements were used to characterize the newly fabricated palm fatty acid adorned magnetic Fe3O4 nanoparticles (MNP-FA). The obtained results confirmed the successful synthesis of palm fatty acid-functionalized magnetic nanoparticles. Oil removal tests performed with MNP-FA revealed that this newly prepared material could selectively adsorb lubricating oil up to 3.5 times of the particles' weight while completely repelling water. The main parameters affecting the adsorption of oil i.e., sorption time, mass of sorbent and pH of water were optimized.
Recently, the graphite based materials have gained interest as excellent platforms to remove aqueous pollutants via adsorption routes. This is given that such materials possess large specific surface area and low density. In the present work, a comparative study of two facile and effective approaches is conventional thermal heating and microwave irradiation methods to fabricate expanded graphite from available flake graphite sources of Vietnam for oil-contaminated water purification. The as-prepared expanded graphite was characterized by using FT-IR, SEM, XRD and BET analysis. The results exhibited that expanded graphite has multilevel pore structures and the surface area of expanded graphite obtained from microwave irradiation and conventional heating was 147.5 (m²/g) and 100.97 (m²/g) under optimal processing conditions. The as-synthesized expanded graphite from the microwave irradiation method was found to have higher adsorption capacities for diesel oil, crude oil, and fuel oil compared to conventional heating method.
The adsorption of residue oil from palm oil mill effluent (POME) using chitosan powder and flake has been investigated. POME contains about 2g/l of residue oil, which has to be treated efficiently before it can be discharged. Experiments were carried out as a function of different initial concentrations of residue oil, weight dosage, contact time and pH of chitosan in powder and flake form to obtain the optimum conditions for the adsorption of residue oil from POME. The powder form of chitosan exhibited a greater rate compared to the flake type. The results obtained showed that chitosan powder, at a dosage of 0.5g/l, 15min of contact time and a pH value of 5.0, presented the most suitable conditions for the adsorption of residue oil from POME. The adsorption process performed almost 99% of residue oil removal from POME. Equilibrium studies have been carried out to determine the capacity of chitosan for the adsorption of residue oil from POME using the optimum conditions from the flocculation at different initial concentrations of residue oil. Langmuir and Freundlich adsorption models were applied to describe the experimental isotherms and isotherm constants. Equilibrium data fitted very well with the Freundlich model. The pseudo first- and second-order kinetic models and intraparticle diffusion model were used to describe the kinetic data and the rate constants were evaluated. The experimental data fitted well with the second-order kinetic model, which indicates that the chemical sorption is the rate-limiting step, i.e. chemisorption between residue oil and chitosan. The significant uptake of residue oil on chitosan was further proved by BET surface area analysis and SEM micrographs.
The presence of heavy metal and radionuclides in water bodies has been a long-lasting environmental problem which results in many undesirable consequences. In this framework, the biosorption process, which uses inexpensive and naturally produced material such as alginate, is an alternative technology in the environmental remediation. This review provides relevant and recent literature regarding the application of alginate and its derivatives on removal of various heavy metal ions and radionuclides. The effects of process variables such as solution pH, adsorbent dosage, metal ion concentration, contact time, temperature and co-existing ions used in batch studies in addition to kinetic, isothermal models as well as thermodynamic that fit the adsorption experimental data are critically discussed. This review also includes mechanisms involved during adsorption process. Furthermore, future research needs for the removal of contaminants by alginate-based materials with the aims of improving their adsorption performance and their practical applications are commented.
In this study, we evaluated and characterized microbial cellulose produced from Kombucha after eighth day of fermentation by employing SEM, FTIR, X-ray diffractometry, adsorption isotherm, and by measuring the swelling properties. Results on SEM revealed microbial cellulose layer to be composed of a compact cellulose ultrafine network like structure. FTIR spectra showed the presence of a characteristic region of anomeric carbons (960 – 730 cm-1), wherein a band at 891.59 cm-1 confirmed the presence of β, 1-4 linkages. Results of FTIR spectra also showed microbial cellulose to be free from contaminants such as lignin or hemicellulose, which are often present in plant cellulose. X-ray diffraction studies exhibited the overall degree of crystallinity index for MCC to be slightly lower than that of microbial cellulose. Results on swelling properties indicated microbial cellulose to possess higher fiber liquid retention values (10-160%) compared to commercial MCC (5-70%). The adsorption isotherm curves showed similarities between microbial cellulose with that of pure crystalline substance. Overall, results obtained in this study were comparable with the commercial microcrystalline cellulose, indicating that the process developed by us can be explored industrially on a pilot scale.
In this study, chitosan/polyvinyl alcohol (PVA)/zeolite nanofibrous composite membrane was fabricated via electrospinning. First, crude chitosan was hydrolyzed with NaOH for 24h. Afterward, hydrolyzed chitosan solution was blended with aqueous PVA solution in different weight ratios. Morphological analysis of chitosan/PVA electrospun nanofiber showed a defect-free nanofiber material with 50:50 weight ratio of chitosan/PVA. Subsequently, 1wt.% of zeolite was added to this blended solution of 50:50 chitosan/PVA. The resulting nanofiber was characterized with field emission scanning electron microscopy, X-Ray diffraction, Fourier transform infrared spectroscopy, swelling test, and adsorption test. Fine, bead-free nanofiber with homogeneous nanofiber was electrospun. The resulting membrane was stable in distilled water, acidic, and basic media in 20 days. Moreover, the adsorption ability of nanofibrous membrane was studied over Cr (VI), Fe (III), and Ni (II) ions using Langmuir isotherm. Kinetic parameters were estimated using the Lagergren first-order, pseudo-second-order, and intraparticle diffusion kinetic models. Kinetic study showed that adsorption rate was high. However, the resulting nanofiber membrane showed less adsorption capacity at high concentration. The adsorption capacity of nanofiber was unaltered after five recycling runs, which indicated the reusability of chitosan/PVA/zeolite nanofibrous membrane. Therefore, chitosan/PVA/zeolite nanofiber can be a useful material for water treatment at moderate concentration of heavy metals.
Multiwall carbon nanotubes (MWCNTs) were synthesized using a tubular microwave chemical vapor deposition technique, using acetylene and hydrogen as the precursor gases and ferrocene as catalyst. The novel MWCNT samples were tested for their performance in terms of Pb(II) binding. The synthesized MWCNT samples were characterized using Fourier Transform Infrared (FT-IR), Brunauer, Emmett and Teller (BET), Field Emission Scanning Electron Microscopy (FESEM) analysis, and the adsorption of Pb(II) was studied as a function of pH, initial Pb(II) concentration, MWCNT dosage, agitation speed, and adsorption time, and process parameters were optimized. The adsorption data followed both Freundlich and Langmuir isotherms. On the basis of the Langmuir model, Qmax was calculated to be 104.2mg/g for the microwave-synthesized MWCNTs. In order to investigate the dynamic behavior of MWCNTs as an adsorbent, the kinetic data were modeled using pseudo first-order and pseudo second-order equations. Different thermodynamic parameters, viz., ∆H(0), ∆S(0) and ∆G(0) were evaluated and it was found that the adsorption was feasible, spontaneous and endothermic in nature. The statistical analysis revealed that the optimum conditions for the highest removal (99.9%) of Pb(II) are at pH5, MWCNT dosage 0.1g, agitation speed 160r/min and time of 22.5min with the initial concentration of 10mg/L. Our results proved that microwave-synthesized MWCNTs can be used as an effective Pb(II) adsorbent due to their high adsorption capacity as well as the short adsorption time needed to achieve equilibrium.
The application of magnetized graphene (G) layers synthesized on the carbon nanofibers (CNFs) (m-G/CNF) was investigated as novel adsorbent for the magnetic solid-phase extraction (MSPE) of polycyclic aromatic hydrocarbons (PAHs) in water samples followed by gas chromatography-flame ionization detector (GC-FID). Six important parameters, affecting the extraction efficiency of PAHs, including: amount of adsorbent, adsorption and desorption times, type and volume of the eluent solvent and salt content of the sample were evaluated. The optimum extraction conditions were obtained as: 5min for extraction time, 20mg for sorbent amount, dichloromethane as desorption solvent, 1mL for desorption solvent volume, 5min for desorption time and 15% (w/v) for NaCl concentration. Good performance data were obtained at the optimized conditions. The calibration curves were linear over the concentration ranges from 0.012 to 100ngmL(-1) with correlation coefficients (r) between 0.9950 and 0.9967 for all the analytes. The limits of detection (LODs, S/N=3) of the proposed method for the studied PAHs were 0.004-0.03ngmL(-1). The relative standard deviations (RSDs) for five replicates at two concentration levels (0.1 and 50ngmL(-1)) of PAHs were ranged from 3.4 to 5.7%. Appropriate relative recovery values, in the range of 95.5-99.9%, were also obtained for the real water sample analysis.
A radiotracer study was conducted to investigate the removal characteristics of cadmium (109Cd) from aqueous solution by polypyrrole/ sawdust composite. Several factors such as solution pH, sorbent dosage, initial concentration, contact time, temperature and interfering metal ions were found to have influence on the adsorption process. The kinetics of adsorption was relatively fast, reaching equilibrium within 3 hours. A lowering of the solution pH reduced the removal efficiency from 99.3 to ~ 46.7% and an ambient temperature of 25°C was found to be optimum for maximum adsorption. The presence of sodium and potassium ions inhibited 109Cd removal from its aqueous solution. The experimental data for 109Cd adsorption showed a very good agreement with the Langmuir isotherm and a pseudo-first order kinetic model. The surface condition of the adsorbent before and after cadmium loading was investigated using BET, FESEM and FTIR. Considering the low cost of the precursor's materials and the toxicity of 109Cd radioactive metal, polypyrrole synthesized on the sawdust of Dryobalanops aromatic could be used as an efficient adsorbent for the removal of 109Cd radioisotope from radionuclide-containing effluents.
The feasibility for the removal of Acid Blue25 (AB25) by Bengal gram fruit shell (BGFS), an agricultural by-product, has been investigated as an alternative for high-cost adsorbents. The impact of various experimental parameters such as dose, different dye concentration, solution pH, and temperature on the removal of Acid Blue25 (AB25) has been studied under the batch mode of operation. pH is a significant impact on the sorption of AB25 onto BGFS. The maximum removal of AB25 was achieved at a pH of 2 (83.84%). The optimum dose of biosorbent was selected as 200 mg for the removal of AB25 onto BGFS. Kinetic studies reveal that equilibrium reached within 180 minutes. Biosorption kinetics has been described by Lagergren equation and biosorption isotherms by classical Langmuir and Freundlich models. Equilibrium data were found to fit well with the Langmuir and Freundlich models, and the maximum monolayer biosorption capacity was 29.41 mg g(-1) of AB25 onto BGFS. The kinetic studies indicated that the pseudo-second-order (PSO) model fitted the experimental data well. In addition, thermodynamic parameters have been calculated. The biosorption process was spontaneous and exothermic in nature with negative values of ΔG° (-1.6031 to -0.1089 kJ mol(-1)) and ΔH° (-16.7920 kJ mol(-1)). The negative ΔG° indicates the feasibility of physical biosorption process. The results indicate that BGFS could be used as an eco-friendly and cost-effective biosorbent for the removal of AB25 from aqueous solution.
The presence of Cs(I) ions in nuclear wastewater becomes an important issue for the reason of its high toxicity. The development of adsorbent embedded metal-based catalysts that has sufficient adsorption capacity is expected for the removal of Cs(I) ions from contaminated water. This study tested the use of maghemite, titania and combined maghemite-titania polyvinyl alcohol (PVA)-alginate beads as an adsorbent to remove Cs(I) ions from aqueous solution with the variables of pH and initial concentration using batch experiments under sunlight. The results showed that the use of combined maghemite-titania PVA-alginate beads can have an efficiency of 93.1% better than the use of either maghemite PVA-alginate beads with an efficiency of 91.8% or titania PVA-alginate beads with an efficiency of 90.1%. The experimental data for adsorption of Cs(I) ions from aqueous solution with the initial concentrations of 50, 100 and 200 mg L(-1) on the surface of combined maghemite-titania PVA-alginate beads were well fit by the pseudo-second-order and Langmuir models. The optimal adsorption of Cs(I) ions from aqueous solution by combined maghemite-titania PVA-alginate beads under sunlight occurs at pH 8 with an initial Cs(I) ion concentration of 50 mg L(-1). The combined maghemite-titania PVA-alginate beads can be recycled at least five times with a slight loss of their original properties.
In vitro Lead (Pb(2+)) binding capacity of two probiotic bacteria strains, namely Bifidobacterium longumBB79 and Lactobacillus pentosusITA23, was assessed following incubation with the intestinal contents (IC) of laying hens. Results of this study demonstrated that IC treatment significantly enhanced (P<0.01) Pb(2+) binding capacity of both bacterial strains. Fourier transform infrared analysis indicated that several functional groups (O-H or N-H, C-H, C˭O, C-O, and C-O-C) on the bacteria cell wall involved in metal ion binding were altered after IC incubation, and new groups appeared between the 3700cm(-1) and 4000cm(-1)bands. Transmission electron microscopy demonstrated that after incubation with IC, unidentified IC components created new binding sites on the bacterial cell surface. These particles also changed the mechanism of Pb(2+) binding of the two strains from intracellular accumulation to extracellular adsorption.
Layered double hydroxide (LDH) with Mg/Al molar ratio of 4/1 (MAN-4) was synthesized by co-precipitation and followed by hydrothermal method. The compound was allowed to undergo ion exchange with K2HPO4 for 48 hours to produce MgAlHPO4 (MAHP-4). The solid produced was characterized using X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR). Adsorption of copper solution by MAHP-4 was carried out using batch experiment by mixing the copper solution and the sorbent MAHP-4. The effects of
various parameters such as contact time, pH, adsorbent dosage and initial concentration were investigated. The optimum pH for copper removal was found to be 4 and the optimum time of copper removal was found at 4 hours. The isotherm data was analysed using model isotherm Langmuir with the correlation coefficient of 0.999 was recorded. The maximum adsorption capacity, Qo (mg/g) of 142.8 mg/g was also recorded from the Langmuir isotherm. The remaining copper solution was determined by using EDXRF (Energy Dispersive XRay Fluorescence spectrometry) model MiniPal 4 (PAN analytical). The results in this study indicate that MAHP-4 has potential as an effective adsorbent for removing copper from aqueous solution.