Removal of mercury(II) from wastewater using camel bone charcoal

Efficiency of chemically activated raw and calcined waste fish bone for adsorption of Cd (II) and Pb (II) from polluted water

Bone biochar is used as an adsorbent in water pollution control because of its high surface area and pore volumes. This study is attempting to prepare a low-cost adsorbent from waste fish bones by chemical activation and use it for the removal of Cd2+ and Pb2+ from polluted water. The preparation of fish bone adsorbents involved two methods. The first method includes the chemical activation of waste fish bone using different chemical activators (0.001 M HNO3, 0.1 M NaOH, 0.5% H2O2, and ethanol) (FB), while the second one includes the calcination of waste fish bone after the chemical activation at 873 K (FB-Hy). The synthesized fish bone adsorbent (FB) was characterized by electron microscopy (SEM), X-ray diffractometer (XRD), X-ray fluorescence (XRF), Brunauer–Emmett–Teller (BET) surface area, and Fourier transform infrared (FT-IR). The effectiveness of the prepared adsorbent (FB) in removing Pb and Cd was evaluated based on contact time, solution pH, solution temperature, initial metal concentration, and adsorbent dose. Metal concentrations were measured by atomic absorption spectroscopy. The results show that 0.1 M NaOH activation of bone waste (FB) is suitable for higher adsorption of Cd2+ and Pb2+ compared with other activators. The maximum adsorption of Pb and Cd with the FB adsorbent was 99.74 and 99.35%, respectively, at optimum conditions (pH 6.0, contact time 30 min, initial metal concentration 10 ppm, adsorbent dosage 0.1 g, and temperature at 328 K). The results of kinetic adsorption obeyed a pseudo-second-order model. Freundlich and Langmuir isotherms were applied, and the adsorption was found to fit well with the Langmuir model. This study ended with the success of preparing an eco-friendly and low-cost fish bone adsorbent from the waste fish bone and using it for the removal of Cd2+ and Pb2+ from polluted water.

Clam shell waste recycling and valorization for sustainable Hg remediation

Shellfish aquaculture world production is constantly growing due to the increase in demand for seafood and reached over 18 million tons in 2022. The suitable management of the shell waste is one of the main environmental challenging issues as most of this waste is sent to landfills with emanation of foul odors, pathogens proliferation and reduction of available space. However, the conversion of this biowaste to new value-added materials could provide significant environmental and economic benefits. Clam shell waste was the starting material for the synthesis of hydroxyapatite (CSHAP) applied as an adsorbent for Hg2+ removal from aqueous solutions. Adsorption experiments were performed in batch using simulated wastewaters prepared from HgCl2 to investigate the effects of contact time and initial Hg2+ concentration on the removal process. Mineralogical composition, morphological features and elemental composition of CSHAP before and after the experiments were investigated by XRPD, SEM-EDS and FTIR analysis. The concentrations of Hg2+ and Ca2+ in the solutions were analyzed by ICP-AES. The adsorption kinetics of Hg2+ was simulated with the pseudo-first-order rate model, the pseudo-second order model and the intraparticle diffusion model. The results of the kinetics study showed that the Hg2+ adsorption followed the pseudo-second-order kinetics model and reached equilibrium within 40 min. The Langmuir model fitted the experimental results better than the Freundlich, Temkin and Dubinin-Radushkevic isotherm models, with a maximum adsorption capacity of 65.8 mg/g which is generally higher than other waste-derived adsorbents used for the removal of Hg2+ ions from water. The removal mechanism includes rapid surface complexation on CSHAP grains, followed by a slow incorporation of the Hg2+ ions in the crystalline structure. The results of this study could contribute to delineate a new research direction for a more sustainable management of clam shell biowaste.

Adsorption characteristics and applications of andesite in removing some pollutants from wastewater

Andesite was employed to effectively extract mercury(II) in an aqueous solution. After evaluating its characteristics, andesite was characterized by applying modern techniques such as BET and TGA methods. The study employed SEM and TEM measurements to analyze the variation in the surface shape and crystallinity of the metal due to adsorption. Using the EDX process, the chemical composition, weight, and atomic percentage of each element of andesite were determined. FTIR techniques were also used to confirm the TEM-EDX findings. Zeta potential was estimated. Cycles of regeneration and desorption have been examined. 99.03% was the highest uptake percentage. Adsorbent quantity (0.0025-0.05) g/L, contact time (5-60) min, pH (2-10), temperature (25-60) °C, and dose (0.0027, 0.0044, 0.0125, 0.0155, and 0.0399) mg/L all affect the amount of removal that increases with the increase in contact time, pH, dose, and temperature but drops as the metal ion concentration rises. The ideal values for contact time, pH, metal ion concentration, dose, and temperature were found to be, respectively, 30 min, 0.0155 mg/l, 0.02 g/l, and 40 °C. The calculation of thermodynamic parameters, including ΔH, ΔG, and ΔS, was imperative in establishing that the mechanism of heavy metal adsorption on andesite was endothermic, exhibiting a physical nature that escalated with temperature rise. The Freundlich adsorption equation's linear form is matched by the adsorption of mercury(II) on andesite; constant n was 1.85, 1.06, 1.1, and 1.1, whereas the Langmuir constant qm was found to be 1.85, 2.41, 3.54, and 2.28 mg/g at 25-60 °C. Furthermore, adsorption follows a pseudo-second-order rate constant of (3.08, 3.24, 3.24, and 13) g/mg/min under identical temperature conditions, as opposed to a first-order rate constant of 4, 3, 2.6, and 2. Hg2+, NH4+, Cl-, Br-, NO3-, SO42-, Na+, K+, H2S, and CH3SH were all extracted from wastewater by this application.

Comprehensive assessment of carbon-, biomaterial- and inorganic-based adsorbents for the removal of the most hazardous heavy metal ions from wastewater

Owing to the high cost of recycling waste, underdeveloped countries discharge industrial, agricultural, and anthropogenic effluents without pretreatment. As a result, pollutant-loaded waste enters water bodies. Among the diverse toxic contaminants, heavy metal ions are the most detrimental because of their chronic toxicity, non-degradability, prevalence, and bioaccumulation. The growing shortage of water resources demands the removal of heavy metal ions from wastewater. Three SDGs of the sustainability agenda of the United Nations appeal for clean water to protect life beneath water and on land depending on the water sources. Therefore, efficient environmentally friendly approaches for wastewater treatment are urgently required. In this regard, several methods have been developed for the removal of heavy metal ions from wastewater, including adsorption as the most widely used method owing to its eco-friendly, cost-effective, and sustainable nature. The present review discusses the progress in the preparation and application of various adsorbents based on carbon, micro-organisms, agricultural waste and inorganic materials for the extraction of toxic metal ions such as Pb2+, Cr6+, As3+, As5+, Hg2+ and Cd2+. Herein, we provide information on the role of the homogeneity and heterogeneity of adsorbents, kinetics of the adsorption of an adsorbate on the surface of an adsorbent, insights into adsorption reaction pathways, the mechanism of the sorption process, and the uptake of solutes from solution. The present review will be useful for researchers working on environmental protection and clean environment.

The predictive machine learning model of a hydrated inverse vulcanized copolymer for effective mercury sequestration from wastewater

Inverse vulcanized polysulfides (IVP) are promising sulfur-enriched copolymers with unconventional properties irresistible for diverse applications like Hg2+ remediation. Nevertheless, due to their inherent hydrophobic nature, these copolymers still offer low Hg2+ uptake capacity. Herein, we reported the synthesis of IVP by reacting molten sulfur with 4-vinyl benzyl chloride, followed by their functionalization using N-methyl D-glucamine (NMDG) to increase the hydration of the developed IVP. The chemical composition and structure of the functionalized IVP were proposed based on FTIR and XPS analysis. The functionalized IVP demonstrated a high mercury adsorption capacity of 608 mg/g (compared to <26 mg/g for common IVP) because of rich sulfur and hydrophilic regions. NMDG functionalized IVP removed 100 % Hg2+ from a low feed concentration (10-50 mg/l). A predictive machine learning model was also developed to predict the amount of mercury removed (%) using GPR, ANN, Decision Tree, and SVM algorithms. Hyperparameter and loss function optimization was also carried out to reduce the prediction error. The optimized GPR algorithm demonstrated high R2 (0.99 (training) and 0.98 (unseen)) and low RMSE (2.74 (training) and 2.53 (unseen)) values indicating its goodness in predicting the amount of mercury removed. The produced functionalized IVP can be regenerated and reused with constant Hg2+ uptake capacity. Sulfur is the waste of the petrochemical industry and is abundantly available, making the functionalized IVP a sustainable and cheap adsorbent that can be produced for high-volume Hg2+ remediation. ENVIRONMENTAL IMPLICATION: This research effectively addresses the removal of the global top-priority neurotoxic pollutant mercury, which is toxic even at low concentrations. We attempted to remove the Hg2+ utilizing an inexpensive adsorbent developed by NMDG functionalized copolymer of molten sulfur and VBC. A predictive machine learning model was also formulated to predict the amount of mercury removal from wastewater with only a 0.05 % error which shows the goodness of the developed model. This work is critical in utilizing this low-cost adsorbent and demonstrates its potential for large-scale industrial application.

Efficiency of chemically activated raw and calcined waste fish bone for Adsorption of Cd(II) and Pb(II) from polluted water.. [DOI: 10.21203/rs.3.rs-3103669/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Bone biochare is used widely as an adsorbent in water pollution control; because of its high surface area and pore volumes . This study is attempting to prepare a low cost adsorbent from waste fish bone by chemical activation, and uses it for the removal of Pb and Cd from polluted water. Two methods were used for preparation of fish bone adsorbents. The first method includes the chemical activation of waste fish bone using different chemical activators ( 0.001 M HNO3, 0.1 M NaOH, 0.5 % H2O2, and ethanol), while the second one includes calcination of waste fish bone after the chemical activation at 600oC. The synthesized fish bone adsorbents were characterized by electron microscopy (SEM), X-ray diffractometer (XRD), X-ray fluorescence (XRF), BET surface area, and Fourier transform infrared (FT-IR). The efficiency of the prepared adsorbents for removal of Pb and Cd were investigated as a function of contact time, solution pH, solution temperature, initial metal concentration, and adsorbent dose. Metal concentrations were measured by atomic absorption spectroscopy . The results reveal that activation of the waste fish bone by 0.1 M NaOH is the suitable for the higher adsorption of Pb and Cd than with the other activators. The maximum adsorption of Pb and Cd on the chemically prepared adsorbent were 99.74 and 99.35 % , respectively at optimum conditions. The results of kinetic adsorption obeyed a pseudo-second-order model. Freundlich and Langmuir isotherms were applied , and the adsorption was found to be fitted well with the Langmuir model. This study ended with the success for preparing an ecofriendly and low cost fish bone adsorbent from the waste fish bone, and used it for the removal of Pb and Cd from polluted water

Characterization of Date Seed Powder Derived Porous Graphene Oxide and Its Application as an Environmental Functional Material to Remove Dye from Aqueous Solutions

This study aims to prepare graphene oxide (GO) from raw date seeds (RDSs), considered one of the available agricultural wastes in Saudi Arabia. The preparation method is done by the conversion of date seeds to lignin and then to graphite which is used in a modified Hummer's method to obtain GO. The adsorption of insoluble phenothiazine-derived dye (PTZS) over raw date Seeds (RDSs) as a low-cost adsorbent was investigated in this study. X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) were used to characterize (RDSs). According to the calculations, Freundlich isotherms and pseudo-second-order accurately predicted the kinetic rate of adsorption. The adsorption ability was 4.889 mg/g, and the removal rate was 93.98% GO-date Seeds mass, 11 mg/L starting dye concentration, at a temperature of 328 K, pH 9, and contact length of 30 min by boosting the PTZS solution's ionic strength. In addition, the computed free energies revealed that the adsorption process was physical. Thermodynamic calculations revealed that dye adsorption onto GO-date seeds was exothermic and spontaneous.

Value-added materials recovered from waste bone biomass: technologies and applications

As the world population increases, the generation of waste bones will multiply exponentially, increasing landfill usage and posing health risks. This review aims to shed light on technologies for recovering valuable materials (e.g., alkaline earth material oxide such as CaO, hydroxyapatite, beta tri-calcium phosphate, phosphate and bone char) from waste bones, and discuss their potential applications as an adsorbent, catalyst and catalyst support, hydroxyapatite for tissue engineering, electrodes for energy storage, and phosphate source for soil remediation. Waste bone derived hydroxyapatite and bone char have found applications as a catalyst or catalyst support in organic synthesis, selective oxidation, biodiesel production, hydrocracking of heavy oil, selective hydrogenation and synthesis of bioactive compounds. With the help of this study, researchers can gather comprehensive data on studies regarding the recycling of waste bones, which will help them identify material recovery technologies and their applications in a single document. Furthermore, this work identifies areas for further research and development as well as areas for scaling-up, which will lead to reduced manufacturing costs and environmental impact. The idea behind this is to promote a sustainable environment and a circular economy concept in which waste bones are used as raw materials to produce new materials or for energy recovery.

Superior removal of humic acid from aqueous stream using novel calf bones charcoal nanoadsorbent in a reversible process

While the potable water disinfection regimen has significantly reduced waterborne diseases, development of disinfection byproducts (DBP) during this process has brought a global threat to the environment and human health. The most notorious water pollutant, humic acid (HA), transforms into carcinogenic byproducts during the disinfection process (chlorination) of water treatment. HA removal methods are neither economic nor widely available. This study addresses the most urgent global issue of HA removal by developing an innovative and self-regenerative process based on a low-cost and self-regenerative calf bone char (CBC) that removed 92.1-100% of HA. CBC-based HA removal has not been described yet. The developed CBC, as a super adsorbent of HA, was initially characterized by a scanning electron microscope. Various parameters of adsorption/desorption and self-regeneration of CBC adsorbent were experimentally determined. Results show that prepared CBC with a 112 m²/g surface area exhibited adsorption of 38.08 mg/g (HA = 20 mg/L, pH = 4.0) which is several folds higher than the typical amount of HA present in water. The 30 m reaction time was enough to remove HA which is the shorter HA time in comparison to other similar studies. The increase of HA from 0.5 to 5 g/L, raises % HA removal (36.7-99.8%) while a pH decrease (10-4) increases adsorption (12.3-98.3%). The adsorption data fitted well with the pseudo-second-order model and the Langmuir isotherm which demonstrate that adsorption takes place by a monolayer formation. Thermodynamic constants supported the endothermic, spontaneous and reversible nature of adsorption which can attain 100% HA removal. 100% regeneration of exhausted CBC by NaOH further supports the sustainability of the process. CBC as a new adsorbent material thus provides an economical and sustainable water pre-treatment procedure. The present study provides technical guidance for building a cost-effective and scalable process capable of providing clean water.

Kanchan Arsenic Filters for Household Water Treatment: Unsuitable or Unsustainable?

This article critically evaluates the conventional Kanchan Arsenic Filter (KAF) in order to determine the main reasons for its reported poor performance. The KAF was introduced in 2004 in Nepal and makes use of non-galvanized nails as a Fe0 source for As removal. As early as 2009, the KAF was demonstrated to be ineffective for As removal in many cases. This was unambiguously attributed to the Fe0 layer which is placed on top of a sand filter instead of being incorporated into a sand matrix. Despite this conceptual mistake, the conventional KAF has been largely distributed in Asia, and recent articles have assessed its sustainability. This study reiterates that the suitability of the technology, rather than its sustainability, should be addressed. Evidence shows that the KAF has the following design limitations: (i) uses iron nails of unknown reactivity, and (ii) operates on the principle of a wet/dry cycle. The latter causes a decrease in the corrosion rate of the used nails, thereby limiting the availability of the iron corrosion products which act as contaminant scavengers. Taken together, these results confirm the unsuitability of the conventional KAF. Besides correcting the design mistakes, more attention should be paid to the intrinsic reactivity of the used iron nails, including using alternative Fe0 materials (e.g., iron filings, steel wool) for filters lasting for just 6 or 18 months. Specific design considerations to be addressed in the future are highlighted.

Enhancement of anaerobic fermentation with corn straw by pig bone-derived biochar

Different sources of biochar exhibit different effects on anaerobic fermentation. Here, the effects of activation temperature, activation time, impregnation ratio, and pickling times on the properties of pig bone-derived biochar additives were explored by orthogonal experiments. The pig bone-derived biochar with better performance was optimized to enhance the anaerobic fermentation. The results showed that when the preparation conditions of biochar were as follows: activation temperature of 700 °C, impregnation ratio of 2, activation time of 90 min, and pickling times of 2, the cumulative methane production of corn stalk by anaerobic fermentation exhibited the highest value of 164.54 mL/g VS, which was 68% higher than the control group. The correlation between the characteristics of biochar for promoting anaerobic fermentation and the performance of anaerobic fermentation was established. Interestingly, the pig bone-derived biochar can buffer pH value in straw anaerobic fermentation.

Kinetics, isotherm and chemical speciation analysis of Hg(Ⅱ) adsorption over oxygen-containing MXene adsorbent

A facile method was used to prepare two-dimensional MXene for the treatment of heavy metal ions in wastewater. The adsorbent has good selectivity for the adsorption of Hg (Ⅱ) in mixed divalent cationic metal solutions due to a large number of oxygen-containing functional groups on the surface of the material. The adsorption of mercury was tested using mercuric chloride and mercury nitrate solutions. The Langmuir maximum adsorption capacity of the adsorbent at a pH of 5.0 and a temperature of 30 °C is 1057.3 mg/g (mercuric nitrate) and 773.29 mg/g (mercuric chloride), respectively. The adsorbent also maintains a high adsorption capacity at low pH (pH = 2.0). The removal rate of mercury-containing wastewater within 100 mg/L is nearly 100%. The chemical species of Hg-containing ions at different pH and temperatures was studied. It was found that the adsorbent could maintain a high adsorption capacity for different forms of Hg-containing ions.

Comparative evaluation of bone chars derived from bovine parts: Physicochemical properties and copper sorption behavior

With the increasing demand for beef worldwide, a considerable amount of bovine bone is discharged as solid waste. Therefore, in this study, the physicochemical properties of chars from bovine bones (ribs, scapulae, vertebrae, and legs) and their copper sorption behavior in aqueous solutions were investigated. The bone chars were pyrolyzed at 500 °C and the ash contents were approximately 85.08%, although the leg bone char had significantly higher values. The rib bone char showed a larger specific surface area (172 m²/g), smaller average pore diameter (7.7 nm), and more basic functional groups than the other char types. The maximum sorption capacity varied from 72.53 to 83.71 g/kg, with the rib bone char exhibiting the best adsorption characteristics, followed by the scapulae, vertebrae, and legs. A correlation analysis demonstrated that the adsorption capacity of Cu(II) on bone char is closely related to surface pore characteristics. An adsorption kinetic analysis and physicochemical characterization of the chars indicate that the Cu(II) adsorption mechanism in bovine bone char is primarily surface chemisorption. Based on the different of physicochemical properties and sorption behavior, bone chars pyrolyzed from bovine ribs are most suitable for adsorption-related applications. The results of this study demonstrate the potential for classified utilization of animal bones, including the use of graded bone chars as low-cost adsorbents requiring no chemical pre-treatment.

Evaluation of hydroxyapatite/poly(acrylamide-acrylic acid) for sorptive removal of strontium ions from aqueous solution

A composite polymer, hydroxyapatite/poly(acrylamide-acrylic acid), was synthesized by gamma-induced polymerization. The factors affecting the sorption process were evaluated. The removal increased with time and achieved equilibrium after 1 h for all initial concentration ranges (10-50 mg/L). The highest removal of Sr(II) was achieved using 50 mg/L at pH 6. The sorption process was found to follow a pseudo-first-order mechanism. The equilibrium data are best described by the Langmuir model, with a monolayer capacity of 53.59 mg/g. The values of thermodynamic parameters indicate that the sorption process is endothermic (ΔH > 0), increases randomness (ΔS > 0) and is spontaneous (ΔG < 0). The results imply that the composite could be used as a promising low-cost material for the removal of radionuclides from radioactive waste.

Kinetics and Adsorption Studies of Mercury and Lead by Ceria Nanoparticles Entrapped in Tamarind Powder

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.

Adsorption of terpenic compounds onto organo-palygorskite

Essential oils from aromatic plants are currently mentioned as suitable tools for excellent protection of stored grains from insect pest attacks. The present work aimed to study the processes of the synthesis insecticidal formulation with clay. The active terpenic compounds of essential oil of Eucalyptus globulus (Eg) were fixed in the palygorskite by adsorption process. Two sample types of palygorskites were used: raw and organo-palygorskite. The palygorskite clays were characterized by different physicochemical techniques including X-ray diffraction (XRD), Fourier transform infrared (FTIR) analyses, thermogravimetric analysis (TG), differential thermal analysis (DTA), Brunauer-Emmet-Teller (BET), and scanning electron microscope (SEM). Results reveal that the raw clay has a fibrous structure with impurities essential calcite. These structures and physicochemical properties of raw palygorskite and organo-palygorskite give it the potential of material adsorbent. Results show that the adsorption capacity strongly depends on affinity between terpenic compounds and organic cations rather than on interlayer distance of organo-palygorskite. The highest adsorption capacity of terpenic compounds is acquired with palygorskite interlaced by didodecyldimethylammonium bromide (DDDMA). These results validated the potential utility of the Paly-DDDMA as adsorbent fibrous clay for the retention of terpenic compounds in application of environmental preservation.

Adsorption/reduction of Hg(II) and Pb(II) from aqueous solutions by using bone ash/nZVI composite: effects of aging time, Fe loading quantity and co-existing ions

In this research, a versatile and highly efficient method for the stabilization of nanoscale zerovalent iron particles (nZVI) on the surface of ostrich bone ash (OBA) was presented as a novel inorganic adsorbent (OBA/nZVI) for the removal of Hg(II) and Pb(II) ions from aqueous solutions, even after 1 year of storage under room conditions. The removal behavior of the OBA/nZVI was assessed as a function of the initial pH, contact time, initial pollutants concentration, temperature, amount of adsorbent, effect of competitive metal ions, and ionic strength. The synthesized adsorbent was characterized by several techniques including N₂ adsorption at - 196 °C, FT-IR spectroscopy, scanning electron microscopy, X-ray diffraction, and zeta potential. The results confirmed that the OBA is a good candidate as support of nZVI. The maxima adsorption capacity for Hg(II) and Pb(II) ions found from experimental results were 170 and 160 mg g^-1, when the loading quantities of Fe were 20%. The equilibrium sorption data obeyed a Langmuir-Freundlich isotherm type model. The kinetic data of the adsorption followed the mechanism of the pseudo-second-order model. The thermodynamic experiments indicated that the removal of metal ions were feasible, endothermic, and spontaneous. It can be found that fresh and aged OBA/nZVI maintained its usability even after five cycles in the order: fresh (OBA/nZVI)-Hg(II) > fresh (OBA/nZVI)-Pb(II) > aged (OBA/nZVI)-Hg(II) > aged (OBA/nZVI)-Pb(II), which indicate that OBA/nZVI can be regenerated as adsorbent. The existence of Fe in the OBA/nZVI was proved by SEM-EDX results and X-ray diffraction analysis also confirmed adsorption/reduction of some of the Hg(II) to Hg⁰ and Pb(II) to Pb⁰.

Adsorption of Hg(II) and Pb(II) ions by nanoscale zero valent iron supported on ostrich bone ash in a fixed-bed column system

In this research, ostrich bone ash (OBA) was modified with nanoscale zerovalent iron (nZVI) particles and applied as a novel composite adsorbent (OBA/nZVI) for dynamic adsorption/reduction of Hg(II) and Pb(II) ions in a fixed-bed column system. Entrapment of nZVI in OBA beads barricades the particles from oxidation and aggregation. The dynamic behavior of metal ions removal by OBA/nZVI was assessed as a function of inlet flow rates, bed height, initial pollutants concentration and pH. The synthesized OBA/nZVI composite was characterized by several physicochemical techniques. Increase in pH and bed height and decrease in flow rates and initial metal concentration resulted in delay of breakthrough time. OBA breakthrough profile is sharper than the OBA/nZVI breakthrough curve for both metal ions and the breakthrough times increase in the order OBA/nZVI-Hg(II) > OBA/nZVI-Pb(II) > OBA-Pb(II) > OBA-Hg(II). Based on the experiment results, redox reaction is expected to occur to a certain extent, as the standard reduction potentials of Hg(II) and Pb(II) are more than that of Fe(II). From a practical point of view, the OBA/nZVI could be applied as a material to remove Hg(II) and Pb(II) ions from natural surface and ground water with a pH value of 5-9.

Rational design, fabrication and characterization of a thiol-rich 3D-porous hypercrosslink polymer as a new engineered Hg2+ sorbent: enhanced selectivity and uptake

A new synergy between a porous matrix and active sites was developed to form a heterogeneous adsorbent for high efficiency and high selectivity mercury removal in drinking water.

Removal of mercury(II) ions in aqueous solution using the peel biomass of Pachira aquatica Aubl: kinetics and adsorption equilibrium studies

Mercury is a highly toxic substance that is a health hazard to humans. This study aims to investigate powders obtained from the peel of the fruit of Pachira aquatica Aubl, in its in natura and/or acidified form, as an adsorbent for the removal of mercury ions in aqueous solution. The materials were characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. The infrared spectra showed bands corresponding to the axial deformation of carbonyls from carboxylic acids, the most important functional group responsible for fixing the metal species to the adsorbent material. The thermograms displayed mass losses related to the decomposition of three major components, i.e., hemicellulose, cellulose, and lignin. The adsorption process was evaluated using cold-vapor atomic fluorescence spectrometry (CV AFS) and cold-vapor atomic absorption spectrometry (CV AAS). Three isotherm models were employed. The adsorption isotherm model, Langmuir-Freundlich, best represented the adsorption process, and the maximum adsorption capacity was predicted to be 0.71 and 0.58 mg g(-1) at 25 °C in nature and acidified, respectively. Adsorption efficiencies were further tested on real aqueous wastewater samples, and removal of Hg(II) was recorded as 69.6 % for biomass acidified and 76.3 % for biomass in nature. Results obtained from sorption experiments on real aqueous wastewater samples revealed that recovery of the target metal ions was very satisfactory. The pseudo-second-order model showed the best correlation to the experimental data. The current findings showed that the investigated materials are potential adsorbents for mercury(II) ion removal in aqueous solution, with acidified P. aquatica Aubl being the most efficient adsorbent.

Surfactant-free green synthesis of Fe3O4 nanoparticles capped with 3,4-dihydroxyphenethylcarbamodithioate: stable recyclable magnetic nanoparticles for the rapid and efficient removal of Hg(ii) ions from water

A 3,4-dihydroxyphenethylcarbamodithioate capped biogenic Fe₃O₄ magnetic nanocomposite has been synthesized using a watermelon rind extract for the removal of Hg(ii) ions with a facile recyclability.

Electroless nickel coated nano-clay for electrolytic removal of Hg(ii) ions

The footprint existence and accumulation of cataclysmic Hg(ii) ions in aqueous media poses a severe threat to biological ecosystems and necessitates immediate measures for its regulation.

Mercury removal using ground and calcined mussel shell

We determined mercury retention on calcined and ground mussel shell, in presence and absence of phosphate, using batch and stirred flow chamber experiments. In batch experiments the calcined shell exhibited higher Hg adsorption, with good fitting to Freundlich equation (R2: 0.925-0.978); the presence of phosphate increased Hg adsorption; mercury desorption was 13% or lower, diminishing up to 2% under the presence of phosphates. In stirred flow chamber experiments calcined shell retained more Hg than ground shells (6300 vs. 4000-5200 micromol/kg); Hg retention increased an additional 40% on calcined shell and up to an additional 70% on ground shells when phosphates were present; mercury desorption was quite similar in all shell types (20%-34%), increasing up to 49%-60% in ground shells when phosphates were present. The higher Hg adsorption on calcined shell would be related to its calcite and dolomite concentrations; mercury-phosphate interactions would cause the increase in Hg retention when phosphates are present. Data on Hg desorption suggest that Hg retention was not easily reversible after batch experiments, increasing in the stirred flow chamber due to convective flow. Calcined and ground mussel shells could be recycled removing Hg from water, with the presence of phosphates in solution improving efficacy.

Modeling Pb (II) adsorption from aqueous solution by ostrich bone ash using adaptive neural-based fuzzy inference system

To evaluate the performance of Adaptive Neural-Based Fuzzy Inference System (ANFIS) model in estimating the efficiency of Pb (II) ions removal from aqueous solution by ostrich bone ash, a batch experiment was conducted. Five operational parameters including adsorbent dosage (C(s)), initial concentration of Pb (II) ions (C(o)), initial pH, temperature (T) and contact time (t) were taken as the input data and the adsorption efficiency (AE) of bone ash as the output. Based on the 31 different structures, 5 ANFIS models were tested against the measured adsorption efficiency to assess the accuracy of each model. The results showed that ANFIS5, which used all input parameters, was the most accurate (RMSE = 2.65 and R(2) = 0.95) and ANFIS1, which used only the contact time input, was the worst (RMSE = 14.56 and R(2) = 0.46). In ranking the models, ANFIS4, ANFIS3 and ANFIS2 ranked second, third and fourth, respectively. The sensitivity analysis revealed that the estimated AE is more sensitive to the contact time, followed by pH, initial concentration of Pb (II) ions, adsorbent dosage, and temperature. The results showed that all ANFIS models overestimated the AE. In general, this study confirmed the capabilities of ANFIS model as an effective tool for estimation of AE.

Adsorption of Hg(II) from Aqueous Solution Using Adulsa (Justicia adhatoda) Leaves Powder: Kinetic and Equilibrium Studies

The ability of Adulsa leaves powder (ALP) to adsorb Hg(II) from aqueous solutions has been investigated through batch experiments. The ALP biomass was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The experimental parameters that were investigated in this study included pH, adsorbent dosage, and effect of contact time along with initial metal ion concentration. The adsorption process was relatively fast, and equilibrium was achieved after 40 min of contact time. The maximum removal of Hg(II), 97.5% was observed at pH 6. The adsorption data were correlated with Langmuir, Freundlich, and Temkin isotherms. Isotherms results were amply fitted by the Langmuir model determining a monolayer maximum adsorption capacity (qm) of ALP biomass equal to 107.5 mg g−1and suggesting a functional group-limited sorption process. The kinetic process of Hg(II) adsorption onto ALP biomass was tested by applying pseudofirst-order, pseudosecond-order, Elovich, and intraparticle-diffusion models to correlate the experimental data and to determine the kinetic parameters. It was found that the pseudosecond order kinetic model for Hg(II) adsorption fitted very well. The rate determining step is described by intraparticle diffusion model. These studies considered the possibility of using Adulsa plant leaves biomass as an inexpensive, efficient, and environmentally safe adsorbent for the treatment of Hg(II) contaminated wastewaters.

Fast and efficient removal of mercury from water samples using magnetic iron oxide nanoparticles modified with 2-mercaptobenzothiazole

Mercury in the lowest levels of concentrations is dangerous for human health due to its bioaccumulation in body and toxicity. This investigation shows the effective removal of mercury (II) ions from contaminated surface waters by modified magnetic iron oxide nanoparticles (M-MIONPs) with 2-mercaptobenzothiazole as an efficient adsorbent. The proposed method is fast, simple, cheap, effective and safe for treatment of mercury polluted waters. Preparation of adsorbent is easy and removal time is short. Non-modified magnetic iron oxide nanoparticles (MIONPs) can adsorb up to 43.47% of 50 ngmL(-1) of Hg (II) ions from polluted water, but modified magnetic ironoxide nanoparticles (M-MIONPs) improved the efficiency up to 98.6% for the same concentration. The required time for complete removal of mercury ions was 4 min. Variation of pH and high electrolyte concentration (NaCl) of the solution do not have considerable effect on the mercury removal efficiency. Loading capacity of adsorbent for Hg ions is obtained to be 590 μgg(-1).

Mercury adsorption on granular activated carbon in aqueous solutions containing nitrates and chlorides

Adsorption is an effective process to remove mercury from polluted waters. In spite of the great number of experiments on this subject, the assessment of the optimal working conditions for industrial processes is suffering the lack of reliable models to describe the main adsorption mechanisms. This paper presents a critical analysis of mercury adsorption on an activated carbon, based on the use of chemical speciation analysis to find out correlations between mercury adsorption and concentration of dissolved species. To support this analysis, a comprehensive experimental study on mercury adsorption at different mercury concentrations, temperatures and pH was carried out in model aqueous solutions. This study pointed out that mercury capture occurs mainly through adsorption of cationic species, the adsorption of anions being significant only for basic pH. Furthermore, it was shown that HgOH(+) and Hg(2+) are captured to a higher extent than HgCl(+), but their adsorption is more sensitive to solution pH. Tests on the effect of temperature in a range from 10 to 55 °C showed a peculiar non-monotonic trend for mercury solution containing chlorides. The chemical speciation and the assumption of adsorption exothermicity allow describing this experimental finding without considering the occurrence of different adsorption mechanisms at different temperature.

Removal of mercury(II) from aqueous solution using moss (Drepanocladus revolvens) biomass: equilibrium, thermodynamic and kinetic studies

The equilibrium, thermodynamics and kinetics of the biosorption of Hg(II) onto moss (Drepanocladus revolvens) biomass from aqueous solution were investigated. Optimum experimental parameters were determined to be pH 5.5, contact time 60min, biomass concentration 4 g L(-1) of solution, and temperature 20 degrees C. From the Langmuir model the maximum biosorption capacity of the moss biomass was found to be 94.4 mg g(-1). The mean free energy value (10.2 kJ mol(-1)) evaluated by using the Dubinin-Radushkevich (D-R) model indicated that the biosorption of mercury ions onto D. revolvens was taken place by chemical ion-exchange. The kinetic studies indicated that the biosorption process of mercury ions followed well pseudo-second-order model. The calculated thermodynamic parameters (DeltaG degrees , DeltaS degrees , DeltaH degrees ) showed the biosorption to be exothermic and spontaneous with decreased randomness at the solid-solution interface. The recovery of the Hg(II) from D. revolvens biomass was found to be 99% using 1M HCl. It was concluded that the D. revolvens biomass can be used as biosorbent for the treatment of wastewaters containing Hg(II) ions.

Biosorptive removal of mercury(II) from aqueous solution using lichen (Xanthoparmelia conspersa) biomass: kinetic and equilibrium studies

The potential use of the lichen biomass (Xanthoparmelia conspersa) to remove mercury(II) ions from aqueous solution by biosorption was evaluated using the batch method. Effects of pH, contact time, biomass concentration and temperature on the removal of Hg(II) ions were studied. The Langmuir isotherm models defined the equilibrium data precisely compared to Freundlich model and the maximum biosorption capacity obtained was 82.8 mg g(-1). From the D-R isotherm model, the mean free energy was calculated as 9.5 kJ mol(-1). It shows that the biosorption of Hg(II) ions onto X. conspersa biomass was taken place by chemical ion-exchange. Experimental data were also performed to the pseudo-first-order and pseudo-second-order kinetic models. The results indicated that the biosorption of Hg(II) on the lichen biomass followed well the second-order kinetics. Thermodynamic parameters, DeltaG(o), DeltaH(o) and DeltaS(o) indicated the Hg(II) sorption to be exothermic and spontaneous with decreased randomness at the solid-solution interface. Furthermore, the lichen biomass could be regenerated using 1M HCl, with up to 85% recovery, which allowed the reuse of the biomass in ten biosorption-desorption cycles without any considerable loss of biosorptive removal capacity.