Microwave-assisted preparation of carboxylic graphene oxide-chitosan composite for adsorption of uranium and heavy toxic metals in water samples

This study involved investigation and comparison of the capacity of garlic and ginger particles in adsorption of lead, cadmium and chromium ions from contaminated water. This was motivated by the perennial contamination of well water by crude oil, which carried alongside heavy metals from earth surface and other sources in contact with it while discharging from oil facilities to the subsurface region. Heavy metal analysis on the well water and crude oil from the polluted site showed high level of heavy contamination. Effect of initial concentration of heavy metals, adsorbents dosage and contact time on adsorption of the lead, cadmium and chromium ions in aqueous solution by garlic and ginger particles were studied. Garlic and ginger particles adsorption process was studied using Langmuir and Temkin isotherms. Also, to describe the kinetics of the adsorption process, the Pseudo first and second order kinetics as well as the intra-particle diffusion kinetics were used to study the experimental data. The analysis showed that the percentage of lead, cadmium and chromium ions adsorbed by garlic and ginger particles decreased as the initial concentration of metals in solution and contact time were increased. Similarly, the percentage of lead, cadmium or chromium ions adsorbed by the garlic and ginger particles at equilibrium increased as adsorbent dosages was increased due to increased effective surface area of the adsorbent. Equilibrium was attained at about 60 minutes with either garlic or ginger particles. However, garlic particles adsorbed the heavy metals more than the particles of ginger at all conditions. Also, it was observed that lead ion has more affinity to both garlic and ginger particles followed by cadmium ion. The adsorption of lead, cadmium and chromium ions were better explained by the Langmuir isotherm model than the Temkin’s isotherm model. The maximum adsorption capacity for lead, cadmium and chromium ions with garlic particles were 3.9308 mg/g, 3.3223 mg/g and 1.992 mg/g while that of ginger particles were 2.9011 mg/g, 2.3121 mg/g and 1.9543 mg/g respectively. The adsorption of lead, cadmium and chromium ions in the solution of both adsorbents revealed that diffusion and chemisorptions occurred in the adsorption process, which was best fitted in the Pseudo second order kinetics. Indicating that the Pseudo second order kinetics was the rate controlling step, and thus, will predict accurately the concentration of metal ions adsorbed. Conclusively, the garlic and ginger particles showed capacity for the removal of lead, cadmium and chromium in aqueous solution, and therefore are recommended for use in adsorption of heavy metals in wastewater. Keywords : Garlic, Ginger, Heavy metals, Adsorption Isotherm, Kinetics DOI : 10.7176/CPER/60-04 Publication date :March 31 st 2019

Heavy metals are the most dangerous inorganic pollutants Due to their bioaccumulation and their nonbiodegradability, for this, several studies have focused on the recovery of these metals from water using different techniques. In this context, our study consists of evaluating an efficient and eco-friendly pathway of competitive recovery of heavy metals (Cd, Cr and As) from aqueous solutions by adsorption using raw rock. This adsorbent was characterized before and after the adsorption process by several techniques. The multi-metals adsorption process in the batch mode was undertaken to evaluate the effect of adsorbent mass, contact time, pH, Temperature, and initial heavy metals concentration. The kinetic data were analyzed using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetic models. According to the modeling of the experimental results, the adsorption kinetics of heavy metals were adapted to the pseudo-second-order model. The adsorption isotherms were evaluated by the Langmuir and Freundlich isotherm models. The experimental isotherm data of heavy metals were better fitted with the Langmuir model rather than Freundlich isotherm models. The maximum experimental adsorption capacities (Qmax) predicted by the Langmuir model are 15.23 mg/g for Cd (II), 17.54 mg/g for Cr (VI) and 16.36 mg/g for As (III). The values of thermodynamic parameters revealed that the heavy metals adsorption was exothermic, favorable, and spontaneous in nature. The desorption process of heavy metals showed that this raw rock had excellent recycling capacity. Based on the results, these untreated clays can be used as inexpensive and environmentally friendly adsorbents to treat water contaminated by heavy metals.

Isotherm models for adsorption of heavy metals from water - A review

Investigation of the adsorption of heavy metals (Cu, Co, Ni and Pb) in treatment synthetic wastewater using natural clay as a potential adsorbent (Sale-Morocco)

The aim of this work is to detect the best operating conditions that effect on the removal of Cu2+, Zn2+, and Ni2+ ions from aqueous solution using date pits in the batch adsorption experiments. The results have shown that the Al-zahdi Iraqi date pits demonstrated more efficient at certain values of operating conditions of adsorbent doses of 0.12 g/ml of aqueous solution, adsorption time 72 h, pH solution 5.5 ±0.2, shaking speed 300 rpm, and smallest adsorbent particle size needed for removal of metals. At the same time the particle size of date pits has a little effect on the adsorption at low initial concentration of heavy metals. The adsorption of metals increases with increasing the initial of metal concentration while above the 85 ppm, the removal efficiency was decreased. The phenomenon of adsorption of heavy metals on to Al-Zahdi Iraqi Date pits is exothermic process. The maximum adsorption capacity according to the Langmuir equation was 0.21, 0.149, and 0.132 mmol/g for Cu2+, Zn2+, and Ni2+ respectively. The adsorption equilibrium was well described by the Freundlich model. The results of Freundlich constants indicated that the adsorption capacity and adsorption intensity of Copper is larger than the Zinc and Nickel. The intraparticle diffusion was involved is this process but it is not the controlling step. The results of this study may inspire to find the optimal operating conditions for adsorption and develop that with large-scale production to clean the polluted water with heavy metals.

Raw peat was modified with sulfuric acid, then mixed modified with resin to prepare the modified peat-resin particles. Using the batch experimental systems, the removal of heavy metals (copper and lead) on the modified peat-resin particles was investigated. The data of the adsorption isotherm could be fitted by the Langmuir equation well. The adsorption rate of heavy metals on modified peat-resin particles was very swift. The removal processes of heavy metals on modified peat-resin particles could be well described by pseudo-second order model. The adsorption rate of lead was affected by the initial heavy metal concentration, initial pH, particle size, agitation speed and particle mass. In the adsorption of heavy metals (lead and copper) on the modified peat-resin particles, ion exchange was the major reaction mechanism. Desorption data showed that the lead adsorbed by modified peat-resin particle could be desorbed by 0.5 N or 1.0 N HNO3. The desorption rate was swift. The experiments indicated that the modified peat-resin particles have great potential for the removal of heavy metals from wastewater.

Bioremediation of heavy metals from the aqueous environment using Artocarpus heterophyllus (jackfruit) seed as a novel biosorbent

The temperature- and pH-sensitive poly(N-isopropylacrylamide-co-acrylic acid) hydrogels, poly(NIPAM-co-AA), were synthesized by radical polymerization. The characterizations of hydrogels based on N-isopropylacrylamide (NIPAM) and acrylic acid (AA) before and after adsorption of heavy metal ions was performed by Fourier transform infrared spectroscopy and scanning electron microscopy. Heavy metal ions (Cr, Mn, Pb) adsorbed onto poly(NIPAM-co-AA) hydrogels were identified using the energy-dispersive X-ray spectroscopy. The mechanism of the water transport within the matrix of synthesized poly(NIPAM-co-AA) hydrogels at pH 4.5 is Super Case II diffusion, and at pH 6.8 corresponds to the non-Fickian diffusion mechanism. The effect of pH, temperature, contact time, and the initial concentration of heavy metals on the adsorption process of Cr(VI), Mn(II), and Pb(II) ions from aqueous solutions onto poly(NIPAM-co-AA) hydrogels were investigated. The kinetic and equilibrium data were best fitted by the pseudo-second-order model and Langmuir adsorption isotherm. Thermodynamic results indicate that the removal process of heavy metal ions from aqueous solutions by poly(NIPAM-co-AA) hydrogels was spontaneous and exothermic in nature. Maximum adsorption capacities of poly(NIPAM-co-AA) hydrogels for heavy metal ions decrease in the following order: Pb(II) > Cr(VI) > Mn(II).

Heavy metal contamination in the environment and food chain is one of the largest concerns of the twenty-first century and a plant derived adsorbent might provide a sustainable solution to this problem. Psyllium Husk (Isobgul) is already consumed as a natural remedy for the treatment of constipation and other health purposes. The objective of the present study was to modify the surface morphology of Psyllium Husk and its use for the adsorption of heavy metals from aqueous solutions. A binary grafted co-polymer of Psyllium mucilage was successfully synthesized by grafting Acrylic Acid and Acrylonitrile monomers onto the polysaccharide chain under microwave irradiation. FTIR spectroscopy confirmed the formation of different functional groups on the polysaccharide chain. SEM analysis showed increased roughness in surface morphology on modified Psyllium Husk. Batch adsorption tests were conducted using this grafted polymer to analyze its adsorption efficiency of Pb (II), Cr (III) and Cd (II) ion. Atomic Absorption Spectroscopy confirmed up to 79% removal of the Lead (II) ion, 42% removal of Cadmium (II) and 45% removal of Chromium (III) ion from aqueous solutions using 0.1 g of adsorbent in 50 ml solution. The adsorption mechanism was studied by fitting the batch adsorption data against various known isotherms and kinetic models. Results showed that experimental data had a better fit against the Langmuir isotherm for Cd adsorption and against the Freundlich isotherm for Pb and Cr adsorption. The time-dependent lead adsorption data were fitted against the pseudo-first order and pseudo second-order model. R2 values (0.7746 for pseudo first-order and 0.9979 for pseudo second-order) show that the adsorption mechanism closely followed the pseudo secondorder model. The results of this study indicate that the grafting capabilities of Psyllium Husk can be leveraged to create Psyllium Husk-based adsorbent in raw water treatment and may have further applications as dietary supplement that can effectively remove heavy metals from the human body provided that this product does not have any level of toxicity for oral consumption. Chemical Engineering Research Bulletin: 23 (Special): 17-23

Heavy metals in the environment cause adverse effects on living organisms. Agro-wastes have the potential to remove heavy metals from aqueous solutions. In this study, the orange peel cellulose (OPC) beads were utilized as adsorbents to remove metals from wastewater. The surface of the adsorbent was studied by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy coupled with energy dispersive x-ray spectroscopy (SEM-EDS). The concentrations of the metals before and after adsorption were measured using inductively coupled plasma mass spectrometry. The removal of the metal ions (i.e., Cr6+, Cd2+, and Pb2+) using the OPC was investigated by varying the pH, contact time, and adsorbent dosages parameters. The maximum removal efficiency obtained for the metal ions occurred at pHs 4–8. The use of the Langmuir isotherm and Freundlich isotherm models demonstrated the statistical significance of the heavy metal adsorption processes (R2 > 0.96). At a neutral pH, the OPC adsorption order was Pb2+ > Cd2+ > Cr6+ with % removal values of 98.33, 93.91, and 33.50, respectively. The adsorption equilibrium for Cr6+ was reached after 36 h. For Cd2+ and Pb2+, equilibrium was reached after 8 and 12 h, respectively. The FT-IR and SEM-EDS confirmed the presence of many functional groups and elements on the adsorbent. The adsorption of heavy metals using the OPC is a low-cost, eco-friendly, and innovative method for the removal of metals in aquatic environments. The findings of this study will be highly significant for the public in the affected areas worldwide that have credible health concerns due to water contamination with heavy metals.

Discharge of toxic metals such as cadmium (Cu), lead (Pb), and zinc (Zn) in the environment can impact the quality of air and water. High concentration of these toxic metals larger than the regulated concentration in the air and water can pose serious human health risks. The aim of this research was to investigate the removal of these heavy metals (Cd, Pb and Zn) from aqueous solutions by using a multi walled carbon nanotubes modified by chitosan as an absorbent agent. To perform the experimental study, nitrate salt of heavy metals solution prepared with distilled water was used. Factors examined for the removal efficiency of heavy metals in this study include pH, absorbent dose concentration, retention time, and the initial concentration of heavy metals. All analytical analyses were performed according to standard methods. Also, the infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) used for identification and modification of the absorbent. The results obtained from this study showed that an increase in pH, retention time and initial concentration of heavy metals, also increased the adsorption efficiency rate. The optimum heavy metals removal efficiency was about 75% and that occurred when pH =7, retention time =120 minutes and the initial concentration of heavy metals =20 mg/L. In addition, plot of Langmuir and Freundlich adsorption isotherms for heavy metals showed that the adsorption process mostly follows the Freundlich isotherm. The limited data obtained from this experimental sudy, it can be concluded that using carbon nanotubes modified with chitosan as an absorbant agent is an effective method for the removal of heavy metals (Cd, Pb, and Zn) from aqueous solutions.

Background: Today, through various industrial processes, toxic heavy metals are released into aquatic environments that are harmful to the ecosystem. In the present investigation, removal of such contaminants from industrial wastewater is necessary. The purpose was made to extend an ecofriendly technology by using a bio carbon generated from sunflower waste biomass. Methods: The impact of initial pH of solution (2–10), initial heavy metal concentration, and bio carbon dose on the adsorption processes was studied. The residual concentration of samples, Cr(III), Cd(II) and Pb(II) after adding adsorbent and then filteration was determined using atomic absorption spectroscopy. Results: The equilibrium data were found to be well described by the Langmuire model. The Langmuire isotherm feasibility was checked with the dimensionless separation factor (RL). Conclusions: The introduction of a new adsorbent represents a great challenge for both academia and industry, and among all of the methods for removal contamination, we choose adsorption processes. Overall, the work demonstrates the possible use of sunflower waste biomass, as an effective adsorbent for the removal of heavy metals from wastewater.

Microplastics (MPs) and heavy metals are two major types of pollutants that interact with each other, but they are poorly understood. Polystyrene (PS) is one type of MPs that is often detected in aquatic environments. In this study, we examined the adsorption capacity and release rate of heavy metals with respect to different particle sizes of PS, heavy metals, initial heavy metal concentrations, and salinities. Virgin (new) PS with diameters of 20, 50, 130, and 250 μm was used in this study, and four heavy metals (lead, cadmium, copper, and zinc) were used. The results showed that larger PS particle sizes adsorbed more heavy metals even though it took longer to achieve equilibrium adsorption. An increase in heavy metal concentration caused the adsorption capacity (μg g–1) of PS particles to also increase, but the adsorption rate (%) decreased. Increased salinity of the heavy metal solution resulted in a slower adsorption time and a lower adsorption capacity and release rate from the surface of PS particles. Different heavy metals also had different adsorption capacities. Pb was consistently more highly adsorbed by MPs, followed by Cu, Zn, and Cd. Larger PS sizes released heavy metals faster than smaller PS sizes, and the amounts of heavy metals released were higher. The heavy metal with the highest release rate was Cd, followed by Pb, Cu, and Zn. Finally, our findings highlight the interactions between PS and heavy metals and strongly support that PS particles can act as vectors for heavy metals in aquatic systems.

In this paper, the material types were preferentially selected for different kinds of heavy metals, the effect of calcination temperatures on metal adsorption was investigated, and the adsorption mechanism was explored and summarized. The results show that the pseudo-first-order kinetic was better to fit the adsorption of heavy metals. The biomass type and pyrolysis temperature had an effect on the rate at which heavy metals were absorbed. Based on their adsorbed capacity, 350 °C pyrolyzed corn stalk char, 550 °C pyrolyzed peanut shell char, 450 °C pyrolyzed peanut shell char, 450 °C pyrolyzed peanut shell char, and 500 °C pyrolyzed wheat stalk char were shown to be the best adsorbents for Cr2O72-, Cd2+, Cu2+, Zn2+ and Pb2+, respectively. The largest adsorption rate were in the order of Cr6+ (Cr2O72-, 0.5380 /min) > Pb2+ (0.2276 /min) > Cd2+ (0.1354 /min) > Cu2+ (0.1273 /min) > Zn2+ (0.1000 /min), which might be positively related to the ion radius. Meanwhile, the yield of biomass decreased from 43.9% to 29.0% with the increase of pyrolysis temperature from 350 °C to 550 °C. In addition, the specific surface area and functional groups of the biochar, as well as the ionic radius and initial concentration of heavy metals affect the adsorption rate.

Novel green chitosan-pectin gel beads for the removal of Cu(II), Cd(II), Hg(II) and Pb(II) from aqueous solution