Low-cost and efficient adsorbent derived from pyrolysis of Jatropha curcas seeds for the removal of Cu2+ from aqueous solutions

Biochar, is a low-cost material that can be used as an alternative adsorbent for the removal of heavy metals. In this study, a low-cost and efficient adsorbent synthesised from Jatropha curcas seeds was used for the uptake of Cu²⁺ from aqueous solutions. The as-prepared adsorbent was characterised by scanning electron microscopy and Brunauer–Emmett–Teller analysis post calcination at 500 °C, its BET surface area and total pore volume were 39.62?m²?g^?1 and 0.049?m³?g^?1, respectively. Subsequently, the effects of initial pH of the solution, contact time, and adsorbent material dosage on the adsorption of Cu²⁺ by the prepared adsorbent were investigated. The as-prepared adsorbent exhibited a high performance, with a maximum adsorption amount of 32.895?mg?g^?1 for Cu²⁺ at pH 5.0 and 25 °C, owing to the presence of ?OH, C=O, C–O, Si-O-Si, and O-Si-O on its surface. The predominant Cu²⁺ adsorption mechanism was assumed to be ion exchange. Notably, the Cu²⁺ adsorption could attain equilibrium within 90?min. In addition, the fact that the Langmuir model was a better fit than the Freundlich model for the isotherm data of Cu²⁺ adsorption by the as-prepared adsorbent suggested that the adsorption of Cu²⁺ was a monolayer adsorption process.     

Magnetic chitosan/sodium alginate gel bead as a novel composite adsorbent for Cu(II) removal from aqueous solution

Environmental Geochemistry and Health - Using sodium alginate hydrogel as skeleton, in combination with chitosan and magnetic Fe3O4, a new type of magnetic chitosan/sodium alginate gel bead (MCSB)...     

1,3,5-triazine-triethylenetetramine polymer: an efficient adsorbent for removal of Cr(VI) ions from aqueous solution

The synthesis of 1,3,5-triazine-triethylenetetramine (TATETA), its characterization by infrared spectroscopy and elemental analysis, and its application for removal of Cr(VI) ions from aqueous solution is reported. The effects of pH, contact time, initial concentration of Cr(VI), sorbent dose, and temperature on adsorption were investigated and optimized by batch adsorption experiments. Adsorption was highest at acidic conditions with an equilibration time of 25 min. The adsorption followed a Langmuir model, with an adsorption capacity of 303 mg g^?1, was second order in its kinetics, and exothermic and thus spontaneous.     

Glutathione-functionalized melamine sponge,a mimic of a natural antidote,as a quick responsive adsorbent for efficient removal of Hg(II) from aqueous solutions

Minamata disease is caused by methylmercury, which is produced by microorganisms from inorganic mercury ions, Hg(II), in the aquatic environment. Adsorption is a feasible method to remove Hg(II) from waters, but there are some drawbacks when using conventional adsorbents, for example, tedious solid–liquid separation, slow response, and excessive residual levels of mercury. In this work, a novel spongy adsorbent has been developed for Hg(II) removal via surface functionalization of melamine formaldehyde sponge by glutathione. This material mimics a natural antidote that removes trace heavy metals in the human body. Results show that the functionalized sponge displays a 99.99% removal efficiency for low concentrations of Hg(II) of 10 mg/L. As a consequence, the residual Hg concentration is lower than 0.005 mg/L, which is slightly below the standard for total mercury in drinking water, of 0.006 mg/L, formulated by the World Health Organization, and much lower that the discharge regulation standard, of 0.01 mg/L, set by the ministry of environmental protection of China. Adsorption kinetic studies indicate that the functionalized sponge has a fast response. Indeed, the adsorption equilibrium can be reached within 10 min, and about 80% of total adsorption capacities are reached in 1 min. Moreover, the maximum adsorption capacity of the glutathione-functionalized sponge is as high as 240.02 mg/g, as shown by adsorption isotherm. Overall our findings disclose the great potential of the developed sponge adsorbent for rapid and efficient removal of Hg(II) from water.     

Effective removal of Cobalt(II) ions from aqueous solutions and nuclear industry wastewater using sulfhydryl and carboxyl functionalised magnetite nanocellulose composite: batch adsorption studies

A new adsorbent sulfhydryl and carboxyl functionalized magnetite nanocellulose composite [(MB-IA)-g-MNCC] was synthesized by graft co-polymerization of itaconic acid onto magnetite nanocellulose (MNCC) using EGDMA as cross linking agent and K₂S₂O₈ as free radical initiator. The adsorption occurs maximum in the pH 6.5. The best fitted kinetic model was found to be pseudo-second-order kinetics. Therefore the mechanism of Co(II) adsorption onto (MB-IA)-g-MNCC follows ion exchange followed by complexation. The Langmuir model was the best fitted isotherm model for the adsorption of Co(II) onto the (MB-IA)-g-MNCC. Simulated nuclear power plant coolant water samples were also treated with (MB-IA)-g-MNCC to demonstrate its efficiency for the removal of Co(II) from aqueous solutions in the presence of other metal ions. To recover the adsorbed Co(II) ions and also to regenerate the adsorbent to its original state 0.1?M HCl was used as suitable desorbing agent. Six cycles of adsorption-desorption experiments were conducted and was found that adsorption capacity of (MB-IA)-g-MNCC has been decreased from 97.5% in the first cycle to 84.7% in the sixth cycle. Recovery of Co(II) using 0.1?M HCl decreased from 93.2% in the first cycle to 79.3% in the sixth cycle.

Abbreviations: T: absolute temperature; q_e: amount adsorbed at equilibrium; q_t: amount adsorbed at time t; CELL: cellulose; Co: cobalt; C_e: concentration at equilibrium; C_HCl: concentration of HCl; C_NaOH: concentration of NaOH; C_A: concentrations of acid; C_B: concentrations of base; W_g: dry weight of composite; W_i: dry weight of MNCC; DS: energy dispersive spectra; EGDMA: ethylene glycol dimethacrylate; Ce: equilibrium concentration; K_L: equilibrium constant; F: Faradays constant; FTIR: Fourier transform infrared spectra; ΔG^o: free energy change; K_F: Freundlich adsorption capacity; 1/n: Freundlich constant; R: gas constant; D: grafting density; EC_o: initial concentration; IA: itaconic acid; IA-g-MNCC: itaconic acid-grafted-magnetite nanocellulose composite; b: Langmuir constant; MNCC: magnetite nanocellulose composite; Q⁰: Maximum adsorption capacity; (MB-IA)-g-MNCC: 2-mercaptobenzamide modified itaconic acid-grafted-magnetite nanocellulose composite; NC: nanocellulose; pH_pzc: Point of zero charge; K₂S₂O₈: potassium peroxy sulphate; k₁: pseudo-first-order rate constant; k₂: pseudo-second-order rate constant; SEM: scanning Electron Microscope; b_s: Sips adsorption capacity; Q_s: Sips maximum adsorption capacity; ΔH°: standard enthalpy change; ΔS°: standard entropy change; A: surface area; σ₀: surface charge density; 1/n_s: surface heterogeneity factor; VSM: vibrating sample magnetometer; V: volume of solution; W: weight of (MB-IA)-g-MNCC; M_composite: weight of the composite; XRD: X-ray diffraction     

Application of Zr(IV) tungstate for removal of metal ions from aqueous solutions

A heteropolyacid Zr(IV) tungstate-based cation exchanger has been synthesized. An amorphous sample, prepared at pH 1.2 and having a Na⁺ ion exchange capacity of 0.92?meq?g^?1, was selected for further studies. Its physicochemical properties were determined using Fourier transform infrared spectrometer, X-ray diffraction, thermogravimetric, and scanning electron studies. To understand the cation exchange behavior of the material, distribution coefficients (K _d) for metal ions in various solvent systems were determined. Some important binary separations of metal ions, namely Mg²⁺–Bi³⁺, Cd²⁺–Bi³⁺, Fe³⁺–Bi³⁺, Th⁴⁺–Bi³⁺, and Fe³⁺–Zn²⁺, were achieved on such columns. The practical utility of these separations was demonstrated by separating Fe³⁺ and Zn²⁺ ions quantitatively in commercial pharmaceutical formulation. The cation exchanger has been successfully applied also for the treatment of industrial wastewater and a synthetic mixture. All the results suggests that Zr(IV) tungstate has excellent potential for the removal of metals from aqueous systems using packed columns of this material.     

Novel approach to control adsorbent aggregation: iron fixed bentonite-fly ash for Lead (Pb) and Cadmium (Cd) removal from aqueous media

In the present study, a novel approach was used to control zero valent iron aggregation and separation problems by fixing zero valent iron (ZVI) on bentonite-fly ash pellets. For this purpose, porous low cost bentonite-fly ash (BFA) pellets with size of 2.00 cm in length and 0.35 cm in diameter were prepared and fixed with ZVI to manufacture zero valent iron bentonite-fly ash (ZVI-BFA) pellets. Importantly, unlike powdered adsorbents, ZVI-BFA can easily be separated from final effluents when exhausted without any disintegration. The performance of the developed novel adsorbent was investigated for the removal of Pb²⁺ and Cd²⁺ from aqueous media. At 100 mg·L^–1 and 1 g adsorbent, a maximum of 89.5% of Cd²⁺ and 95.6% of Pb²⁺ was removed by ZVI-BFA as compared to 56% and 95% removal by BFA. At 200 mg·L^–1, Cd²⁺ and Pb²⁺ removal by ZVI-BFA was 56% and 99.8% respectively as compared to only 28% and 96% by BFA. Further, the removal kinetics was best fitted for pseudo-second order model. The study provides the basis for improving the removal capacity of porous materials by iron fixation while taking separation ability into consideration.

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Adsorptive removal of Drimarine Red HF-3D dye from aqueous solution using low-cost agricultural waste: batch and column study

This study involves the utilisation of peanut husk for the removal of Drimarine Red HF-3D dye from aqueous solutions. Batch study experiments were conducted with native, HNO₃-treated and Na-alginate-immobilised peanut husk biomass. Maximum dye removal (95.24 mg/g) was obtained with HNO₃-treated biomass. The experimental data were successfully explained with a pseudo-second-order kinetic model for all types of biosorbents. The equilibrium data fitted well to the Freundlich adsorption isotherm model. A thermodynamic study was also carried out to check the nature of the adsorption process. A fixed-bed column study for Drimarine Red HF-3D was carried out to optimise the effect of bed height, flow rate and initial dye concentration using peanut husk biomass. The column study showed that biosorption capacity increased with the increase in initial dye concentration and bed height, but decreased with increased flow rate. Data for Drimarine Red HF-3D were in very good agreement with the bed depth service time model. Fourier transform infrared analysis demonstrated the involvement of different functional groups in dye biosorption. These results showed that peanut husk biomass possessed good potential for the removal of Drimarine Red HF-3D from aqueous solution.     

Preparation of magnetic nanocomposite beads and optimizing the conditions for effective removal of U(VI) from aqueous solutions

Magnetic ion-imprinted polymers (IIPs) were prepared by precipitate polymerization and leached with HCl to remove uranium. Their ability to remove hexavalent uranium from wastewater effluents was studied. Batch adsorption studies to determine the optimum conditions of U(VI) removal were conducted at different levels of sample pH, sorbent amount, agitation time, and initial uranium concentration. It was observed that, under optimum conditions (i.e. pH 4, adsorbent amount of 50 mg, 45 min agitation time, and initial U(VI) concentration of 2 mg L^?1), the maximum removal of U(VI) cations was >98% and 80% for the magnetic IIP and the corresponding magnetic non-imprinted polymers (NIP), respectively. Langmuir and Freundlich isotherms were used to describe the adsorption of U(VI) onto magnetic IIP and NIP. The adsorption capacity of U(VI) was determined to be 1.06 and 0.85 mg g^?1 for the two isotherms, respectively. The order of selectivity was found to be U(VI) > Fe(III) > Pb(II). For six cycles of regeneration and reuse, the magnetic polymers maintained their stabilities with only a 4% loss in the extraction efficiency. The average extraction efficiencies of the magnetic polymers for the spiked acid mine drainage and sewage wastewater effluents were 71% and 58% for the magnetic IIP and NIP, respectively. From powder X-ray diffraction analysis, application of the Scherrer equation yielded magnetic nanoparticles of an average mean diameter of 11.9 nm. Thermo-gravimetric analysis revealed that the HCl-leached magnetic polymers had a magnetite residual weight of 5%.     

Trichoderma harzianum: a green sorbent for Pb(II) uptake from aqueous solutions

This investigation describes the use of specially cultivated, nonliving biomass of Trichoderma harzianum as a biosorbent for the batch removal of Pb(II) from a stirred system under different experimental conditions. The metal removal depended upon pH, sorbent particle size, initial Pb(II) concentration, shaking speed, and sorption time. The optimal experimental conditions for the removal of Pb(II) by T. harzianum with an initial metal concentration of 100 mg L^?1 were obtained at a particle size of 53 μm, a pH of 4.5, a shaking speed of 200 rpm, and a contact time of 720 min. The results were analyzed in terms of adsorption isotherms and kinetic models. The Freundlich isotherm model and pseudo second-order model fitted well in the data. T. harzianum proved to be a good biomaterial for accumulating Pb(II) from aqueous solutions (q = 460 mg g^?1).     

Evaluation of micro- and nano-carbon-based adsorbents for the removal of phenol from aqueous solutions

This work reports on the adsorption efficiency of two classes of adsorbents: nano-adsorbents including carbon nanotubes (CNTs) and carbon nanofibers (CNFs); and micro-adsorbents including activated carbon (AC) and fly ash (FA). The materials were characterized by thermogravimetric analysis, transmission electron microscopy, Brunauer–Emmett–Teller (BET) specific surface area, zeta potential, field emission scanning electron microscopy, and UV spectroscopy. The adsorption experimental conditions such as pH of the solution, agitation speed, contact time, initial concentration of phenol, and adsorbent dosage were optimized for their influence on the phenol. The removal efficiency of the studied adsorbents has the following order: AC > CNTs > FA > CNFs. The capacity obtained from Langmuir isotherm was found to be 1.348, 1.098, 1.007, and 0.842 mg/g of AC, CNTs, FA, and CNFs, respectively, at 2 hours of contact time, pH 7, an adsorbent dosage of 50 mg, and a speed of 150 rpm. The higher adsorption of phenol on AC can be attributed to its high surface area and its dispersion in water. The optimum values of these variables for maximum removal of phenol were also determined. The experimental data were fitted well to Langmuir than Freundlich isotherm models.     

Hydrogels for the removal of the methylene blue dye from wastewater: a review

Environmental Chemistry Letters - Water pollution is a major environmental issue with the rapid development of industry. Therefore, advanced technologies and materials are needed to remove...     

Preparation and characterization of calcium alginate-based composite adsorbents for the removal of Cd,Hg, and Pb ions from aqueous solution

Composite adsorbent materials containing calcium alginate, clinoptilolite, and coal-derived humic acid were prepared. Humic acid (HA), clinoptilolite (CL), alginate (AL), alginate-entrapped humic acid (AL/HA), clinoptilolite (AL/CL), and humic acid/clinoptilolite (AL/HA/CL) samples were characterized. The effectiveness of the samples as adsorbents for the removal of cadmium (Cd), mercury (Hg), and lead (Pb) were studied in a series of batch-adsorption experiments. For the AL, AL/HA, AL/CL, and AL/HA/CL adsorbents, uptake versus time data were evaluated using two kinetic models, a linear and a non-linear pseudo-first-order and a pseudo-second-order model. The data for each metal ion on all adsorbents showed good correspondence with the pseudo-second-order kinetic model. The equilibrium data were fitted to Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin isotherm models. The results show that a non-linear method seems more appropriate for obtaining isotherm parameters. The non-linear Freundlich and Langmuir models for Pb and Hg produced a best fit with high R ² value (0.99). For HA adsorbent, the equilibrium data for Cd removal better fit to the non-linear Dubinin–Radushkevich isotherm.     

Water quality in the Red Sea coastal waters (Egypt): Analysis of spatial and temporal variability

In order to provide a background picture of the water quality of the Egyptian Red Sea a number of hydrological and chemical parameters have been measured bimonthly in 2000. Few data are available on this area, which is apparently subjected to an increasing human impact due to recreational (swimming and diving), industrial (mainly phosphate shipping and industry) and fishing/harbor activities. The results of the present study indicate that changes in the salinity and pH were not significant with highly oxygenated seawaters. The levels of suspended solids (as total suspended matter, TSM) and chlorophyll-a (Chl-a) were generally low and showed an homogeneous distribution in the study region. The ratio of chlorophyll-a to total suspended matter concentrations increased between November and March and decreased from May to September. Chlorophyll-a was significantly correlated with transparency and total suspended matter concentrations in July, September and November. Nitrogen, phosphorus and reactive silicate concentrations were generally low, and allowed classifying the Egyptian Red Sea coastal water as oligotrophic to mesotrophic. The middle region of the study area, which was located between Safaga and Qusair displayed relatively high phosphate contents when compared with other coastal areas. The high values of N:P ratios indicate that PO 4 -P is the limiting factor for phytoplankton growth in the Red Sea coastal waters, with the possible exception of the middle region. Significant relationships were found between chlorophyll-a concentrations and nutrient levels in different sampling periods. Spatial distribution patterns of the studied variables revealed that productivity of the Red Sea coastal waters is mostly controlled by phosphate concentrations, salinity, temperature and dissolved oxygen.     

Removal of Mo(VI) from aqueous solutions using sulfuric acid-modified cinder: kinetic and thermodynamic studies

Removal of Mo(VI) from aqueous solutions was investigated using cinder modified by sulfuric acid. Various parameters such as pH, agitation time, Mo(VI) concentration, and temperature have been studied. The maximum adsorption of Mo(VI) occurred at pH between 4.0 and 6.0. Kinetic studies showed that the adsorption generally obeyed a pseudo second-order model. The activation energy was 31.4?kJ?mol^?1, indicating that the adsorption process was governed mainly by interactions of physical nature. Furthermore, application of Langmuir and Freundlich isotherm models to the adsorption equilibrium data showed that the adsorption behavior obeyed the Langmuir model. The adsorption capacity was found to be 10.8?g Mo(VI)?kg^?1 adsorbent. Finally, thermodynamic parameters such as ΔH ⁰, ΔS ⁰, and ΔG ⁰ were also evaluated, which showed that the adsorption of Mo(VI) on the treated cinder was endothermic, entropy increasing, and spontaneous. In conclusion, the sulfuric acid-modified cinder was shown to be an inexpensive, effective, and simple adsorbent for the removal of Mo(VI) from water.     

Suitability of various chemically prepared activated carbons for the removal of copper(II) ions

Studies on the suitability of various chemically prepared activated carbons (CPACs) like straw carbon (SC), sawdust carbon (SDC), dates nut carbon (DNC) and commercial activated carbon (CAC) for the removal of copper(II) ions by adsorption from simulated wastewater have been carried out under batch mode at 30?±?1°C and the results are compared. The percentage removal of Cu(II) ions increased with a decrease in initial concentration, particle size and added electrolytes (ionic strength) and increased with an increase in contact time, dose of adsorbent and initial pH of the solution. The adsorption data were fitted with the Langmuir isotherm. The applicability of the first order kinetic equation viz. Lagergren equation was tested by correlation analysis. The adsorption process is concluded to be a spontaneous, first order reaction, occurring with increased randomness at the solid–liquid interface. Studies on the desorption of Cu²⁺-loaded activated carbons (ACs) were carried out with nitric acid (0.2–1?N). The possibility of reuse of the regenerated ACs in cycle (in cue-one after another) was tested. SC was found to be a suitable adsorbent alternative to CAC among CPACs for the removal of metal ions, in general, and Cu²⁺ ions, in particular.     

In situ synthesis of FeS/Carbon fibers for the effective removal of Cr(VI) in aqueous solution

• FeS/carbon fibers were in situ synthesized with Fe-carrageenan hydrogel fiber. • The double helix structure of carrageenan is used to load and disperse Fe. • Pyrolyzing sulfate groups enriched carrageenan-Fe could easily generate FeS. • The adsorption mechanisms include reduction and complexation reaction. Iron sulfide (FeS) nanoparticles (termed FSNs) have attracted much attention for the removal of pollutants due to their high efficiency and low cost, and because they are environmentally friendly. However, issues of agglomeration, transformation, and the loss of active components limit their application. Therefore, this study investigates in situ synthesized FeS/carbon fibers with an Fe-carrageenan biomass as a precursor and nontoxic sulfur source to ascertain the removal efficiency of the fibers. The enrichment of sulfate groups as well as the double-helix structure in ι-carrageenan-Fe could effectively avoid the aggregation and loss of FSNs in practical applications. The obtained FeS/carbon fibers were used to control a Cr(VI) polluted solution, and exhibited a relatively high removal capacity (81.62 mg/g). The main mechanisms included the reduction of FeS, electrostatic adsorption of carbon fibers, and Cr(III)-Fe(III) complexation reaction. The pseudo-second-order kinetic model and Langmuir adsorption model both provided a good fit of the reaction process; hence, the removal process was mainly controlled by chemical adsorption, specifically monolayer adsorption on a uniform surface. Furthermore, co-existing anions, column, and regeneration experiments indicated that the FeS/carbon fibers are a promising remediation material for practical application.     

Ecological role for pteroenone,a novel antifeedant from the conspicuous antarctic pteropod Clione antarctica (Gymnosomata: Gastropoda)

Dense populations of the antarctic pteropod Clione antarctica (Smith) offer a rich source of potential nutrients and energy to planktivorous predators. Nonetheless, antarctic fish do not prey on C. antarctica. Employing flash and high-pressure liquid chromatographic techniques, a linear -hydroxyketone, pteroenone (C₁₄H₂₄O₂) was isolated from whole tissues of C. antarctica. When embedded in alginate food pellets at ecologically relevant concentrations, pteroenone caused significant feeding deterrence in Pagothenia borchgrevinki and Pseudotrematomas bernacchii, two antarctic fish known to feed on planktonic organisms. Concentrations of pteroenone were variable between pteropods (0.056 to 4.5 mg ml^-1 tissue), but even those individuals with the lowest natural concentration contained levels five-fold greater than the lowest effective feeding-deterrent concentration (0.012 mg ml^-1 alginate). Chemical analysis indicated that the primary dietary item of the carnivorous C. antarctica, the shelled pteropod Limacina helicina, does not contain pteroenone. This suggests that C. antarctica does not derive this defensive compound from its diet. This is the first example of a defensive secondary metabolite in a pelagic gastropod.     

Acute toxicity and histopathology study of a galactose-specific lectin from the seeds of Tetracarpidium conophorum (African walnut) (Hutch and Dalz)

A lactose-binding lectin (TCL) was purified from the seeds of African walnut, Tetracarpidium conophorum, and acute toxicity studies of the lectin were carried out with Swiss albino male mice. Animals were administered doses of TCL from 500 to 2500?mg?kg^?1 body weight (b.wt.) orally while intraperitoneally the dose ranged from 10 to 600?mg?kg^?1 b.wt. Animals were then assessed for organ and body weight changes, mortality, and histopathology. TCL did not cause any observable toxicity via the oral route; however, when administered intraperitoneally, TCL elicited toxicity with an LD₅₀ of 50?mg?kg^?1 b.wt. Death from intoxication was preceded by convulsion, hypoactivity, salivation, ataxia, and weakness. The animals given lethal doses of the lectin showed profound respiratory depression which was judged to be the primary cause of death. Histopathological analysis indicated that the lungs, liver, and spleen were adversely affected while the kidney and other organs were essentially normal. In all the affected organs, the severity of toxicity was dose-dependent as the effect of the lectin became more pronounced with increase of the dose administered.