Rapid preparation of biosorbents with high ion exchange capacity from rice straw and bagasse for removal of heavy metals.
ABSTRACT: This work describes the preparation of the cellulose phosphate with high ion exchange capacity from rice straw and bagasse for removal of heavy metals. In this study, rice straw and bagasse were modified by the reaction with phosphoric acid in the presence of urea. The introduced phosphoric group is an ion exchangeable site for heavy metal ions. The reaction by microwave heating yielded modified rice straw and modified bagasse with greater ion exchange capacities (∼3.62 meq/g) and shorter reaction time (1.5-5.0 min) than the phosphorylation by oil bath heating. Adsorption experiments towards Pb²⁺, Cd²⁺, and Cr³⁺ ions of the modified rice straw and the modified bagasse were performed at room temperature (heavy metal concentration 40 ppm, adsorbent 2.0 g/L). The kinetics of adsorption agreed with the pseudo-second-order model. It was shown that the modified rice straw and the modified bagasse could adsorb heavy metal ions faster than the commercial ion exchange resin (Dowax). As a result of Pb²⁺ sorption test, the modified rice straw (RH-NaOH 450W) removed Pb²⁺ much faster in the initial step and reached 92% removal after 20 min, while Dowax (commercial ion exchange resin) took 90 min for the same removal efficiency.
Project description:Hydroxyapatite (HAP) was modified with 1-hydroxyethane-1,1-diphosphonic acid (HEDP), and its effect on divalent metal ion binding was determined. HAP was synthesized from calcium hydroxide and phosphoric acid. After calcination, it was modified with HEDP, and the influence of time and temperature on the modification was investigated. HEDP incorporation increased as its initial solution concentration increased from 0.01 to 0.50 M. Unmodified and modified HAP were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and specific surface area analysis. Ca/P ratios, acid capacities, and phosphorus elemental analyses gave the effect of modification on composition and surface characteristics. A high reaction temperature produced new phosphonate bands at 993, 1082, and 1144 cm(-1) that indicated the presence of HEDP. HAP modification at a high temperature-long reaction time had the highest HEDP loading and gave the sharpest XRD peaks. The emergence of new HAP-HEDP strands was observed in SEM images for treated samples while EDS showed high phosphorus contents in these strands. Modified HAP had a high acid capacity from the additional P-OH groups in HEDP. The P(O)OH groups maintain their ability to bind metal ions within the HAP matrix: contacting the modified HAP with 10(-4) N nitrate solutions of five transition metal ions gives an affinity sequence of Pb(II) > Cd(II) > Zn(II) > Ni(II) > Cu(II). This result is comparable to that of commercially available di(2-ethylhexyl)phosphoric acid, a common solvent extractant, and the trend is consistent with the Misono softness parameter of metal ion polarizabilities.
Project description:Reduced graphene oxide (rGO) hybridized with magnetite and/or elemental silver (rGO/magnetite, rGO/silver, and rGO/magnetite/silver) nanoparticles were evaluated as potential adsorbents for toxic heavy metal ions (Cd (II), Ni(II), Zn(II), Co(II), Pb(II), and Cu(II)). Although the deposition of iron oxide and silver nanoparticles on the rGO nanosheets played an inhibitory role in metal ion adsorption, the metal adsorption efficiency by the nanohybrids (NHs) was still higher than that reported for many other sorbents (e.g., activated biochar, commercial resins, and nanosized hydrated Zr(IV) oxide particles). X-ray photoelectron spectroscopy analyses revealed that complexation with deprotonated adsorbents and cation exchange was an important mechanism for Cd(II) ion removal by the rGO and NHs. Competitive adsorption tests using multi metals showed that the adsorption affinity of metal ions on the rGO and its NHs follows the order (Cu(II), Zn(II)) > Ni(II) > Co(II) > (Pb(II), Cd(II)), which is similar to the order observed for single-metal adsorption experiments. These results can be explained by the destabilization abilities of the rGO and NHs, as well as the ionic radii of the considered metal ions. Our findings demonstrate the feasibility of using rGO-based NHs as highly efficient adsorbents for heavy metal removal from water.
Project description:In this study, graphene Th(IV) phosphate was prepared by sol-gel precipitation method. The ion-exchange behavior of this cation-exchanger was studied by investigating properties like ion-exchange capacity for various metal ions, the effect of eluent concentration, elution behavior, and thermal effect on ion-exchange capacity (IEC). Several physicochemical properties as Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) study, thermal studies, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies were also carried out. The material possessed an IEC of 1.56 meq·dry·g-1 of the exchanger and was found to be nano-composite. The selectivity studies showed that the material is selective towards Pb(II) ions. The selectivity of this cation-exchanger was demonstrated in the binary separation of Pb(II) ions from mixture with other metal ions. The recovery was found to be both quantitative and reproducible.
Project description:Lead (Pb) is a ubiquitous pollutant which poses serious threats to plants, animals and humans once entered into the food chain via contaminated industrial effluents on their discharge into the surface of water bodies and/or geological materials. This study aimed to examine and compare the biosorption potential of natural sugarcane bagasse (NB), pyrolysed sugarcane bagasse (PB) and acid assisted pyrolysed sugarcane bagasse (APB) for the removal of Pb from contaminated water. To explore this objective, a series of batch experiments were conducted at various adsorbent mass (0.25, 0.5, 0.75, 1.0 g per 100 ml contaminated water), initial Pb concentration (7, 15, 30, 60 and 120 ppm), and contact time (7, 15, 30, 60 and 120 min). Results revealed that all the tested bio-sorbents have potential to adsorb and remove Pb ions from the contaminated water. In this regard, APB proved more effective since it removed 98% of Pb from aqueous solution at initial Pb concentration of 7 ppm and mass of 0.25 g per 100 ml of aqueous solution. The respective values in case of NB and PB were 90 and 95%. For a given adsorbent type, Pb adsorption decreased by increasing the mass from 0.25 to 1.0 g per 100 ml of aqueous solution. However, the greatest Pb removal occurred at adsorbent mass of 1.0 g per 100 ml of aqueous solution. Initial Pb concentration had a great impact on Pb adsorption and removal by adsorbent. The former increased and the latter decreased with the increase in initial Pb concentration from seven to 120 ppm. At seven ppm Pb concentration, maximum Pb removal took place irrespective to the adsorbent type. Out of the total Pb adsorption and removal, maximum contribution occurred within 15 min of contact time between the adsorbate and adsorbent, which slightly increased till 30 min, thereafter, it reached to equilibrium. Application of equilibrium isotherm models revealed that our results were better fitted with Freundlich adsorption isotherm model. Overall, and for the reasons detailed above, it is concluded that sugarcane bagasse has capabilities to adsorb and remove Pb ions from contaminated water. Its bio-sorption potential was considerably increased after pyrolysis and acid treatment.
Project description:This study aimed to determine effects of rice straw biochar on Pb sequestration in a soil-rice system. Pot experiments were conducted with rice plants in Pb-contaminated paddy soils that had been amended with 0, 2.5, and 5% (w/w) biochar. Compared to the control treatment, amendment with 5% biochar resulted in 54 and 94% decreases in the acid soluble and CaCl2-extractable Pb, respectively, in soils containing rice plants at the maturity stage. The amount of Fe-plaque on root surfaces and the Pb concentrations of the Fe-plaque were also reduced in biochar amended soils. Furthermore, lead species in rice roots were determined using Pb L3-edge X-ray absorption near edge structure (XANES), and although Pb-ferrihydrite complexes dominated Pb inventories, increasing amounts of organic complexes like Pb-pectins and Pb-cysteine were found in roots from the 5% biochar treatments. Such organic complexes might impede Pb translocation from root to shoot and subsequently reduce Pb accumulation in rice with biochar amendment.
Project description:In this study, novel adsorbent ceria nanoparticles (CeNPs) entrapped in tamarind powder (Tm@CeNPs) were efficiently utilized for the simultaneous adsorption of aqueous mercury [Hg(II)] and aqueous lead [Pb(II)]. Surface interactions between the adsorbent and heavy metal ions play an important role in the adsorption process, and the surface morphology can significantly improve the adsorption capacity of the adsorbent. The Langmuir adsorption capacity of Tm@CeNPs for Hg(II) and Pb(II) was found to be 200 and 142.85 mg/g, respectively. The surface area of utilized adsorbent was found to be very high, that is, 412 m2/g. The adsorption kinetics of Tm@CeNPs for both ions follow pseudo-second-order, and the adsorption process is also thermodynamically feasible. Column study favors multilayer adsorption of the heavy metal ion. The spectral analysis of the adsorbent revealed that hydroxyl, carboxylic, and ester groups, as well as CeNPs, are responsible for Hg(II) and Pb(II) adsorption. The cost-benefit analysis confirms the economic viability of the synthesized Tm@CeNPs composite for heavy metal removal. The adsorbent is best suited for Hg(II) adsorption as compared to Pb(II). This is a novel study on the utilization of tamarind leaf powder with CeNPs for heavy metal ion adsorption and its adsorption mechanism, which has not been reported to date.
Project description:In this work, batch adsorption experiments were carried out to investigate the suitability of prepared acid activated carbons in removing heavy metal ions such as nickel(II), lead(II) and chromium(VI). Acid activated carbons were obtained from oil palm and coconut shells using phosphoric acid under similar activation process while the differences lie either in impregnation condition or in both pretreatment and impregnation conditions. Prepared activated carbons were modified by dispersing hydrated iron oxide. The adsorption equilibrium data for nickel(II) and lead(II) were obtained from adsorption by the prepared and commercial activated carbons. Langmuir and Freundlich models fit the data well. Prepared activated carbons showed higher adsorption capacity for nickel(II) and lead(II). The removal of chromium(VI) was studied by the prepared acid activated, modified and commercial activated carbons at different pH. The isotherms studies reveal that the prepared activated carbon performs better in low concentration region while the commercial ones in the high concentration region. Thus, a complete adsorption is expected in low concentration by the prepared activated carbon. The kinetics data for Ni(II), Pb(II) and Cr(VI) by the best selected activated carbon fitted very well to the pseudo-second-order kinetic model.
Project description:In this study, we investigate the adsorption capability of molybdenum sulfide (MoS2)/thiol-functionalized multiwalled carbon nanotube (SH-MWCNT) nanocomposite for rapid and efficient removal of heavy metals [Pb(II) and Cd(II)] from industrial mine water. The MoS2/SH-MWCNT nanocomposite was synthesized by acid treatment and sulfurization of MWCNTs followed by a facile hydrothermal reaction technique using sodium molybdate and diethyldithiocarbamate as MoS2 precursors. Morphological and chemical features of the nanocomposite material were studied using various characterization techniques. Furthermore, the effects of adsorbent (MoS2/SH-MWCNT nanocomposite) concentration, contact time, initial concentration of heavy-metal ions, and reaction temperature were examined to determine the efficiency of the adsorption process in batch adsorption experiments. Kinetics and isotherm studies showed that the adsorption process followed pseudo-second-order and Freundlich adsorption isotherm models, respectively. Thermodynamic parameters calculated using van't Hoff plots show the spontaneity and endothermic nature of adsorption. MoS2/SH-MWCNT nanocomposite demonstrates a high adsorption capacity for Pb(II) (90.0 mg g-1) and Cd(II) (66.6 mg g-1) following ion-exchange and electrostatic interactions. Metal-sulfur complex formation was identified as the key contributor for adsorption of heavy-metal ions followed by electrostatic interactions for multilayer adsorption. Transformation of adsorbent into PbMoO4-x S x and CdMoO4-x S x complex because of the adsorption process was confirmed by X-ray diffraction and scanning electron microscopy-energy-dispersive spectrometry. The spent adsorbent can further be used for photocatalytic and electrochemical applications; therefore, the generated secondary byproducts can also be employed for other purposes.
Project description:In the context of avoiding the use of non-renewable energy sources, employing lignocellulosic biomass for ethanol production remains a challenge. Cellulases play an important role in this scenario: they are some of the most important industrial enzymes that can hydrolyze lignocellulose. This study aims to improve on the characterization of a thermostable Aspergillus fumigatus endo-1,4-β-glucanase GH7 (Af-EGL7). To this end, Af-EGL7 was successfully expressed in Pichia pastoris X-33. The kinetic parameters Km and Vmax were estimated and suggested a robust enzyme. The recombinant protein was highly stable within an extreme pH range (3.0-8.0) and was highly thermostable at 55 °C for 72 h. Low Cu2+ concentrations (0.1-1.0 mM) stimulated Af-EGL7 activity up to 117%. Af-EGL7 was tolerant to inhibition by products, such as glucose and cellobiose. Glucose at 50 mM did not inhibit Af-EGL7 activity, whereas 50 mM cellobiose inhibited Af-EGL7 activity by just 35%. Additionally, the Celluclast® 1.5L cocktail supplemented with Af-EGL7 provided improved hydrolysis of sugarcane bagasse "in natura", sugarcane exploded bagasse (SEB), corncob, rice straw, and bean straw. In conclusion, the novel characterization of Af-EGL7 conducted in this study highlights the extraordinary properties that make Af-EGL7 a promising candidate for industrial applications.
Project description:For further the understanding of the adsorption mechanism of heavy metal ions on the surface of protein-inorganic hybrid nanoflowers, a novel protein-derived hybrid nanoflower was prepared to investigate the adsorption behavior and reveal the function of organic and inorganic parts on the surface of nanoflowers in the adsorption process in this study. Silk fibroin (SF)-derived and copper-based protein-inorganic hybrid nanoflowers of SF@Cu-NFs were prepared through self-assembly. The product was characterized and applied to adsorption of heavy metal ion of Pb(II). With Chinese peony flower-like morphology, the prepared SF@Cu-NFs showed ordered three-dimensional structure and exhibited excellent efficiency for Pb(II) removal. On one hand, the adsorption performance of SF@Cu-HNFs for Pb(II) removal was evaluated through systematical thermodynamic and adsorption kinetics investigation. The good fittings of Langmuir and pseudo-second-order models indicated the monolayer adsorption and high capacity of about 2000 mg g-1 of Pb(II) on SF@Cu-NFs. Meanwhile, the negative values of ? r G m ( T ) ? and ? r H m ? proved the spontaneous and exothermic process of Pb(II) adsorption. On the other hand, the adsorption mechanism of SF@Cu-HNFs for Pb(II) removal was revealed with respect to its individual organic and inorganic component. Organic SF protein was designated as responsible 'stamen' adsorption site for fast adsorption of Pb(II), which was originated from multiple coordinative interaction by numerous amide groups; inorganic Cu3(PO4)2 crystal was designated as responsible 'petal' adsorption site for slow adsorption of Pb(II), which was restricted from weak coordinative interaction by strong ion bond of Cu(II). With only about 10% weight content, SF protein was proven to play a key factor for SF@Cu-HNFs formation and have a significant effect on Pb(II) treatment. By fabricating SF@Cu-HNFs hybrid nanoflowers derived from SF protein, this work not only successfully provides insights on its adsorption performance and interaction mechanism for Pb(II) removal, but also provides a new idea for the preparation of adsorption materials for heavy metal ions in environmental sewage in the future.