Influence of ultrasonication on preparation of novel material for heavy metal removal from wastewater

Dulong People's Traditional Knowledge of Caryota obtusa (Arecaceae): a Potential Starch Plant with Emphasis on Its Starch Properties and Distribution Prediction

The greatest global challenge is to ensure that all people have access to adequate and nutritious food. Wild edible plants, particularly those that provide substitutes for staple foods, can play a key role in enhancing food security and maintaining a balanced diet in rural communities. We used ethnobotanical methods to investigate traditional knowledge on Caryota obtusa, a substitute staple food plant of the Dulong people in Northwest Yunnan, China. The chemical composition, morphological properties, functional, and pasting properties of C. obtusa starch were evaluated. We used MaxEnt modeling to predict the potential geographical distribution of C. obtusa in Asia. Results revealed that C. obtusa is a vital starch species with cultural significance in the Dulong community. There are large areas suitable for C. obtusa in southern China, northern Myanmar, southwestern India, eastern Vietnam, and other places. As a potential starch crop, C. obtusa could substantially contribute to local food security and bring economic benefit. In the future, it is necessary to study the breeding and cultivation of C. obtusa, as well as the processing and development of starch, to solve long-term and hidden hunger in rural areas.

Deposition kinetics of bacteriophage MS2 on Microcystis aeruginosa and kaolin surface

Waterborne virus contamination might easily adsorb on the organic or inorganic surface in the complex aquatic environment. A quartz crystal microbalance coupled with dissipation monitoring was used to investigate the effects of the ionic strength of monovalent cation and divalent cation and pH on the deposition kinetics of bacteriophage MS2 on silica surface coated with Microcystis aeruginosa or kaolin, which represents organic or inorganic particle, respectively. Derjaguin-Landau-Verwey-Overbeek theory was used to illustrate the deposition mechanisms of MS2. The increased concentration of Na⁺ significantly enhanced the deposition rates of MS2 on both coated silica surfaces due to the reduction of repulsive electrostatic interactions. However, the MS2 deposition rates decreased at higher ionic strength of Ca²⁺, which accounted for the steric and hydrophobic interactions. And the higher MS2 deposition rates on both surfaces occurred at pH 3. In addition, the deposition rates of MS2 on kaolin-coated silica surfaces were higher than on the Microcystis-coated surface under all studied conditions. Furthermore, the Derjaguin-Landau-Verwey-Overbeek theory could elucidate the deposition mechanism in Na⁺ solution, whereas the steric and hydrophobic interactions should be considered for the presence of high concentration of Ca²⁺.

A comprehensive review on sources, analysis and toxicity of environmental pollutants and its removal methods from water environment

Natural and human anthropogenic activities increase the concentration of the toxic pollutant in the water environment; they could cause harmful effects even in their lower concentration. In humans, toxic pollutants damage the structural and functional properties of essential organs including the heart, liver, kidneys, reproductive systems and pancreas. To avoid the toxicity of the pollutant, they should be removed from the water environment. Since various conventional water/wastewater treatment technologies including precipitation, ion exchange, flocculation, filtration, electrodialysis and membrane separation are employed to reduce the concentration of the pollutant, they have various difficulties in implementation, efficiency and ecological perspective. Therefore, several researchers are now focusing on alternative and eco-friendly approach called biosorption to remove toxic contaminants from the water environment. The biosorption innovation is one of the acclaimed systems for water treatment. The noteworthy endeavours have been made throughout the years to grow profoundly particular and effective biosorbent materials that are more effective, abundantly available, and cost-effective. Biosorption is effectively executed by utilizing both living and dead biomasses of bacteria, fungi and algae. Moreover, agro-waste materials are also utilized as biosorbents due to their excellent surface properties, abundant availability and cost-effectiveness. A variety of physical and chemical treatments enhances the biosorption capabilities of biosorbents via modifying their surface properties. In this review, biosorption mechanism, influencing parameters and application of biosorbent materials towards the removal of toxic pollutants are discussed. The future research opportunities for sustainable wastewater treatment were also explained.

Simultaneous removal of Cu(II) and reactive green 6 dye from wastewater using immobilized mixed fungal biomass and its recovery

Immobilized fungal biomass (Aspergillus niger and Aspergillus flavus) was prepared and analysed for the simultaneous removal of Cu(II) ion and Reactive Green 6 dye from aqueous phase. Different characterization analysis was utilized to exploit the adsorption characteristics of fungal biomass. Batch biosorption tests, performed to investigate the factors influencing biosorption process inferred optimal values of 25 mg/L of adsorbate with equilibrium time of 60 min, 2.5 g of immobilized fungal biomass, temperature of 303 K and pH of 5.0 for the maximal removal of pollutants. The obtained experimental data was utilized to evaluate the kinetic, thermodynamic and equilibrium models. Langmuir isotherm model has higher correlation coefficient [Cu(II) ion = 0.8625 and RG 6 dye = 0.8575] with small values of errors (RMSE = 3.746 and SSE = 56.12 for Cu(II) ion; RMSE = 4.872 and SSE = 11.87 for RG 6 dye). Kinetic studies performed to evaluate the adsorption rate mechanism of this present study indicated that pseudo-first order and pseudo-second order kinetics to be most fitting model for removal of Cu(II) ions and Reactive green dye respectively. Thermodynamic analysis inferred the spontaneous, random, and exothermic nature of the biosorption process based on ΔG^o, ΔH^o, and ΔS^o values respectively. The prepared biomass can be an alternative for the elimination of toxic pollutants from wastewater.

Ultrasonic assisted agro waste biomass for rapid removal of Cd(II) ions from aquatic environment: Mechanism and modelling analysis

In this research, dragon fruit peel, an agro-waste was used to prepare the new adsorbent for the removal of Cd(II) ions from the aquatic environment. The characterization techniques of SEM, FTIR and EDX for the prepared materials have been studied. The influential parameters for Cd(II) ions were experimented and identified the probable conditions for the maximum adsorption of Cd(II) ions. The investigations on isotherms, kinetics, and thermodynamics for Cd(II) ions removal were examined. Adsorption isotherm data was well discussed with Langmuir model based on the obtained good correlation coefficient and error values. Moreover, it follows the pseudo-first-order and exothermic process. The values of monolayer adsorption capacity of surface-modified dragon fruit peel (SMDFP) and ultrasonic-assisted dragon fruit peel (UADFP) was determined to be 7.469 and 24.76 mg/g at an equilibrium condition, respectively. This study exposed that ultrasonic-assisted dragon fruit peel can be a suitable adsorbent for Cd(II) ions removal from the water environment.

Batch study for Pb2+ removal by polyvinyl alcohol-biochar macroporous hydrogel bead

In this paper, a novel adsorbent which used polyvinyl alcohol, alginate and biochar was successfully made and been used to remove lead from aqueous solutions. Batch experiments were carried out to evaluate the adsorption capacities of Pb (II) on this bead. Experimental data were analysed by the model equations like Langmuir and Freundlich and adsorption kinetic constants were determined using pseudo-first-order (PFO) and pseudo-second-order (PSO). In this study, the adsorption characteristics of Pb (II) were well fitted by the Langmuir isotherm model and pseudo-second-order (PSO) kinetic model. The adsorption of Pb (II) onto PVA-biochar beads are spontaneous and exothermic at 303-333 K by the evidence of the changes in standard Gibbs free energy, standard enthalpy and standard entropy. The maximum adsorption capacity for Pb (II) was estimated to be 176.40 mg/g, which is comparable with other adsorbents. While the maximum adsorption increased varying the pH of initial solution from 2 to 6, the effect on the adsorption amount by the sodium ion concentration is not very large. The results of EDS spectra indicated that the existence of lead in polyvinyl alcohol (PVA)-biochar bead after adsorption, which proving the adsorption of lead. In XPS spectrum, the observed Pb elements also demonstrated that the lead was adsorbed by PVA-biochar bead.

Efficacy of Gamma-Irradiated Macroporous Microbial Biomat for Lead Removal: A Proposed Application to Aquacultures

Lead mobilization in aquaculture and its generated health hazards prompted the use of a cheap and reusable method for its removal within a short duration. A 3D macroporous microbial biomat formed of Trichoderma viride immobilized on luffah was used for Pb removal. The biomat was used to remove 79% of initial 400 mg/kg Pb in 24 h that increased to 87% under optimized conditions of pH, temperature, and contact time. In order to reduce the time needed for Pb bioremoval to 1 h, pretreated biomats were used, resulting in an increase in removal from 58% to 96% upon exposure to gamma radiation (0.01 kilogray [kGy]). The irradiated biomat was studied in terms of morphology, elemental analysis of surface biosorbed Pb and surface functional groups using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and Fourier transform infrared (FTIR) spectroscopy. The results show a difference in the adsorption pattern. The biomat was reused efficiently for 3 consecutive cycles and was also used in fixed bed column showing 89% removal for downward flow and in real aquaculture samples. Pretreated microbial biomats are very suitable for use in fixed bed reactors or as a biofilter and can be tested in recirculating aquaculture systems (RASs), thereby contributing to water conservation and aquaculture sustainability. Integr Environ Assess Manag 2020;16:508-516. © 2020 SETAC.

Electrochemical recovery of cobalt using nanoparticles film of copper hexacyanoferrates from aqueous solution

Nanoparticles film of copper metal hexacyanoferrates (CuHCF) was fabricated to electrochemically separate Co²⁺ in aqueous solutions under various conditions such as applied potential, solution pHs, initial concentrations, contact time and coexisting ions. Results showed that the removal efficiency conducted in reduction potential was obviously higher than that in oxidation potential. The optimal pH for Co²⁺ adsorption occurred at 8.0. Coexisting ions studies revealed that Co²⁺ could be removed from aqueous solutions containing Li⁺, Cu²⁺ and Al³⁺. Considering that cobalt and lithium are the main metallic elements in LiCoO₂, the effect of different ionic strengths (IS) of LiNO₃ (0.5, 1, 2, 5, 10) on adsorption was further investigated. Results showed that IS of LiNO₃ had little impact on the removal efficiency of Co²⁺, which indicated the potential of selective recovery of cobalt from LiCoO₂ in spent lithium-ion batteries. X-ray energy-dispersion spectroscopy (EDS) confirmed that the Co²⁺ could be adsorbed effectively onto CuHCF film. The adsorption was well described by Langmuir isotherm and the maximum sorption capacity is 218.82 mg/g. The kinetic rate of Co²⁺ adsorption was rapid initially and attained equilibrium within 60 min, and the data well fitted the Redlich-Peterson and the Elovich model, implying a chemisorption dominated process.

Enhanced interlayer trapping of Pb(II) ions within kaolinite layers: intercalation, characterization, and sorption studies

Lead (Pb(II)) pollution in water poses a serious threat to human health in many parts of the world. In the past decades, research has been aimed at developing efficient and cost-effective methods to address the problem. In this study, dimethyl sulfoxide (DMSO) and potassium acetate (K-Ac) intercalated kaolinite complexes were synthesized and subsequently utilized for Pb(II) removal from water. The intercalation of kaolinite with DMSO was found to be useful for expanding the interlayer space of the clay mineral from 0.72 to 1.12 nm. Kaolinite intercalation with K-Ac (KDK) increased the interlayer space from 1.12 to 1.43 nm. The surface area of KDK was found to be more than threefold higher as compared to natural kaolinite (NK). Batch experimental results revealed that the maximum Pb(II) uptake capacity of KDK was 46.45 mg g^-1 which was higher than the capacity of NK (15.52 mg g^-1). Reusability studies showed that KDK could be reused for 5 cycles without substantially losing its adsorption capacity. Furthermore, fixed-bed column tests confirmed the suitability of KDK in continuous mode for Pb(II) removal. Successful application of intercalated kaolinite for Pb(II) adsorption in batch and column modes suggests its application in water treatment (especially removal of divalent metals).

Porous Fe0/C ceramsites for removal of aqueous Pb(ii) ions: equilibrium, long-term performance and mechanism studies

This study reports the equilibrium, long-term performance and mechanisms in removing Pb(ii) ions by metallic iron/carbon (Fe0/C) ceramsites (FCC). The Pb(ii) removal equilibrium data was analyzed using the Langmuir, Freundlich and Dubinin-Radushkevich isotherms. At the FCC dosage of 1.14 g L-1, 95.97% of Pb(ii) ions were removed from 50 mg L-1 Pb(ii) solution at initial pH 6.0. The Langmuir isotherm could fit well with the data at initial pH 3.0 with a maximum monolayer adsorption capacity of 112.36 mg g-1 at 25 °C, while the data obtained at initial pH 6.0 could be described by the Freundlich model, indicating multilayer adsorption of Pb species on the FCC. Column tests demonstrated that FCC achieved the highest Pb(ii) removal of 65.86% after 12 days' run compared to 32.35% for Fe0/activated carbon couples and only 1.24% for activated carbon. The X-ray diffraction and X-ray photoelectron spectroscopy analysis revealed that the PbO (dominant Pb species), Pb0, asisite and plumbojarosite appeared after Pb(ii) removal. Scanning electron microscopy with energy dispersive X-ray spectroscopy showed that PbO particles with numerous structures were deposited on the FCC surface in a high amount. The decrease of the Fe/C mass ratio from 7.5 : 1 to 0.298 : 1 revealed that microscale Fe0 could been readily corroded by forming galvanic couples between Fe0 and carbon. The mechanisms of Pb(ii) removal by the FCC were proposed.