Heavy Metal-contaminated Water Research Articles

Agricultural soils of the Animas River watershed after the Gold King Mine spill: An elemental spatiotemporal analysis via portable X-ray fluorescence spectroscopy.

In August 2015, 11.3 million L of heavy metal-contaminated water spilled into the Animas River from the Gold King Mine (Colorado, USA).National attention focused on water quality and agricultural production in areas affected by the spill. In response to local concerns, surface soil elemental concentrations were analyzed in three New Mexico agricultural fields to determine potential threats to agronomic production. Irrigated fields in the Animas watershed were scanned using portable X-ray fluorescence (PXRF) spectrometry to monitor the spatiotemporal variability of Pb, As, Cu, and Cr. A total of 175 locations were scanned using PXRF before and after the growing season for 3 yr. The geostatistical model with the lowest RMSE was chosen as the optimal model. The lowest RMSE for the elements ranged from to 0.10 to 0.44 m for As, from 0.50 to 0.98m for Cr, from 0.15 to 0.91m for Cu, and from 0.14 to 0.44m for Pb across the models selected. The spatial dependence between the measured values exhibited strong to moderate autocorrelation for all metals except for As, for which spatial dependence was strong to weak. Some areas in each field exceeded the New Mexico Environment Department soil screening limit of 7.07mg As kg-1 . All sampling locations were below the screening limit at last sampling time in 2019. Mixed models used for temporal analysis showed a significant decrease only in As below the screening value at the end of the study. Results indicate that the agricultural soils were below the soil screening guideline values.

Spatial Distribution of Heavy Metals and Pollution of Environmental Media Around a Used Lead-acid Battery Recycling Center in Ibadan, Nigeria.

Background.Heavy metals are usually present in trace amounts in various environmental media such as water, soil, and air, and many are poisonous to human health even at very low concentrations.Objectives.To assess the risk of heavy metal contamination of water, soil, and plants around a used lead acid battery (ULAB) recycling center in Ibadan, Nigeria.Methods.Environmental samples (water, soil, and plants) were collected using standard methods and concentrations of arsenic (As), cadmium (Cd), antimony (Sb), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), selenium (Se), and zinc (Zn) were determined using inductively coupled plasma-optical emission spectrometry at the International Institute of Tropical Agriculture, Ibadan, Nigeria.Results.The concentration of metals detected in water samples were higher than permissible limits at more than 50% of the sampling locations. In contrast, heavy metals in soil were within permissible limits. Most of the heavy metals except Pb were found to be present in the plant within permissible limits. Lead levels in water and plants from all locations exceeded the permissible limits. The contamination degree and pollution load index of water sources around the ULAB recycling center indicate a high degree of pollution of water sources with heavy metals, while soil samples were within the normal baseline levels. The transfer factor of Pb from soil to Amaranthus viridis was 1.92. This has implications for human health as the plant is often harvested and for sale in local markets as a source of food and medicine.Conclusions.The present study recommends improved technology for ULAB recycling and adequate treatment of effluent/runoff from recycling centers before discharge.Competing Interests.The authors declare no competing financial interests.

Heavy metal contamination in water of Indus River and its tributaries, Northern Pakistan: evaluation for potential risk and source apportionment

This study investigated the heavy metals (HM) contamination in the water of Indus River and its tributaries, northern Pakistan. Water samples (n=44) were collected along with the five geological units: Kohistan batholith, Chilas complex, Kamila amphibolites, Jijal complex, and Indian plate. Observed HM levels were within the WHO drinking water guidelines except for Ni (23.7 µg/L) in the Jijal complex and Pb (10.6 µg/L) at on the Indian plate. Hazard quotient (HQ) values were observed < 1, suggesting no health risk through water consumption. Statistical analyses revealed that bedrock geology plays a major role in the HM distribution in water of the study area.

Applications of Nanomaterials for Heavy Metal Removal from Water and Soil: A Review

Heavy metals are toxic and non-biodegradable environmental contaminants that seriously threaten human health. The remediation of heavy metal-contaminated water and soil is an urgent issue from both environmental and biological points of view. Recently, nanomaterials with excellent adsorption capacities, great chemical reactivity, active atomicity, and environmentally friendly performance have attracted widespread interest as potential adsorbents for heavy metal removal. This review first introduces the application of nanomaterials for removing heavy metal ions from the environment. Then, the environmental factors affecting the adsorption of nanomaterials, their toxicity, and environmental risks are discussed. Finally, the challenges and opportunities of applying nanomaterials in environmental remediation are discussed, which can provide perspectives for future in-depth studies and applications.

Efficient removal of selenate in water by cationic poly(allyltrimethylammonium) grafted chitosan and biochar composite

The discovery of cheap and eco-friendly functional materials for the removal of anionic heavy metal ions is still challenging in the treatment of heavy metal-contaminated water. Herein, a new poly(allyltrimethylammonium) grafted chitosan and biochar composite (PATMAC-CTS-BC) was introduced for the removal of selenate (SeO42−) in water. Results suggest that the PATMAC-CTS-BC showed a rapid removal of SeO42− with efficiency of >97% within 10 min and it followed a pseudo-second-order model. High capacity of SeO42− adsorption by the composite was achieved, with maximum value of 98.99 mg g−1 based on Langmuir model, considerably higher than most of reported adsorbents. The thermodynamic results reflected the spontaneous and exothermic nature of SeO42− adsorption onto the composite. The composite could be applied at a wide initial pH range (2–10) with high removal efficiency of SeO42− because of permanent positive charges of quaternary ammonium groups (=N+–). The removal mechanisms of SeO42− were mainly attributed to electrostatic interactions with =N+– and protonated –NH3+ groups, and redox-complexation interactions with –NH2, –NH–, and –OH groups. Besides SeO42−, the hexavalent chromium (Cr2O72−) was considered as example to further demonstrate the anion removal capability of cationic hydrogel-BC composite. The study outcomes open up new opportunities to efficiently remove anionic heavy metal ions (e.g., SeO42− and Cr2O72−) in water using these materials.

Assessment of heavy metal contamination in water, sediments, and Mangrove plant of Al-Budhai region, Red Sea Coast, Kingdom of Saudi Arabia

This study investigates the hydrographic parameters and contamination status of zinc (Zn), iron (Fe), copper (Cu), manganese (Mn), lead (Pb), cadmium (Cd), vanadium (V), and nickel (Ni), etc. in surface water, surficial sediments, and mangrove tree tissues (Avicennia marina). Samples were collected from nine sites in Al-Budhai area of Red Sea coast of Jeddah. The trend values of metal contamination factor were Ni (3.23) > Cd (2.99) > Pb (2.86) > Zn (2.69). Translocation factor (TF) of the metals showed Avicennia marina tissues have a dominant role in the phytoremediation process through toxic metal uptake.

Evaluation of alkaline-based activated carbon from Leucaena Leucocephala produced at different activation temperatures for cadmium adsorption

Heavy metal contamination in water is happening worldwide. Adsorption using activated carbon is a common choice for cleaning the wastewater. The drawback of activated carbon is the higher cost of production due to the need for high heat in the process. This work investigated on activated carbon produced from the abundantly available Leucaena leucocephala biomass in order to reduce the cost of raw material. The biomass was chemically activated at different activation temperatures. The produced activated carbon was characterized using SEM, FT-IR, surface analyzer, and TGA. Isothermic and thermodynamic studies were done to evaluate the adsorption properties of the activated carbon. It was found out that higher surface area can be obtained using the higher activation temperature. Higher NaOH to carbonized sample ratios also resulted in higher surface area for all activation temperatures, which are 662 m2g-1 for 700 °C activation temperature, 735 m2g-1 for 750 °C, and 776 m2g−1 for 800 °C. Isothermic studies showed that all of the activated carbon that is produced from Leucaena leucocephala biomass are fit to the Langmuir isotherm, regardless of any activation temperature. Lastly, the thermodynamic study found out the adsorption process is endothermic, reflected by the positive value of ΔHo. It can be concluded that Leucaena leucocephala is a promising alternative material for producing activated carbon.

A simple and rapid algal assay kit to assess toxicity of heavy metal-contaminated water.

This study presents a novel algal-based toxicity test suitable for simple and rapid assessment of heavy metal (Hg2+, Cr6+, Cd2+, Pb2+, or As3+)-contaminated water. A closed-system kit-type algal assay was developed using Chlorella vulgaris. Toxicity was assessed by oxygen evolution in the gaseous phase of the assay kits, which was measured via a needle-type oxygen sensor. Initial cell density, light intensity, and exposure time that enabled favorable test performance for the algal assay kits were 103cells/mL, 250μmolm-2s-1, and 18h, respectively. Results from the heavy metal toxicity tests demonstrate that Hg2+, Cr6+, Cd2+, and Pb2+ are more toxic in inhibiting algal photosynthetic activity than As3+. The 18h half-maximum effective concentrations (EC50) for Hg2+, Cr6+, Cd2+, Pb2+, and As3+ were determined to be 31.3±0.5, 179.6±7.5, 301.3±6.1, 476.1±10.5, and 2184.1±31.1μg/L, respectively. A strong correlation between oxygen concentrations in the headspace of the assay kits and chlorophyll a production indicates that oxygen evolution in the gaseous phase is able to represent algal photosynthetic activity and serve as the end-point in algal toxicity tests. High test sensitivity and reproducibility as well as an easy test protocol and rapid processing time make the algal assay kit a suitable tool for simple and rapid toxicity testing of heavy metal-contaminated water.

One-step synthesis of cake-like biosorbents from plant biomass for the effective removal and recovery heavy metals: Effect of plant species and roles of xanthation

The continuous production of plant wastes and heavy metal pollution of waters have become widespread unavoidable challenges. Reutilization of plant wastes to treat toxic metal-contaminated water is an eco-friendly way to simultaneously solve these problems. Herein, three cake-like biosorbents were synthesized from tea waste, trimmed lawn grass and Nephrolepis cordifolia leaves through a one-step xanthation modification method combined with lyophilization, respectively. The plant species affected the appearance, structure and mechanical strength of the biosorbents due to the different contents of hydrocarbons and inorganic substances, which influenced the gel-like degree and thus the ability of the particles to pack between water molecules. The maximum adsorption capacities of the modified materials for Pb(II), Cu(II) and Cd(II) were 247.20, 85.80 and 265.31 mg/g, respectively, far higher than those of the original wastes, and the adsorption was selective. These results were mainly attributed to newly introduced –(CS)–S–Na groups, which triggered ion exchange, complexation and microprecipitation between heavy metal ions and functional groups. As-prepared biosorbents owned an excellent regenerability, which contributed to recovery heavy metals. The physicochemical properties and adsorption performances of the modified materials indicated that xanthation is a universal modification method suited to different plant biomasses with great potential to purify heavy metal-contaminated water. These biosorbents with excellent separability and regenerability might be promising for continuous-flow sewage treatment.

Effect of Sublethal Concentrations of Cadmium on the Histo-pathological Changes of Muscles of Planiliza abu Juveniles (Heckel, 1843)

Water heavy metals contamination is an international issue due to its detrimental impact on the environment, aquatic organisms and impairment of the ecological balance systems. Cadmium is a heavy metal that is extremely toxic, even in low doses, thus it is a big concern to the ecosystem. Cd can cause several Patho-morphological changes in various organs in fish. This study was evaluated the effect of sublethal concentrations of Cd toxicity and effects on Histopathological of muscle tissues of Planiliza abu Juvenile. Series of Cd concentrations (0.5- 2) ppm were used and the 15d LC50 was 0.4 ppm. Several histopathological alterations were observed which increase gradually with increased concentration, included, marked thickening and hypertrophy of muscle bundle were will observed in lowest concentration (0.5 ppm). While in the highest concentration (2 ppm), atrophy, splitting, and separation with intracellular edema were marked in fish muscle bundle.

Facile synthesis of economical feasible fly ash–based zeolite–supported nano zerovalent iron and nickel bimetallic composite for the potential removal of heavy metals from industrial effluents

Heavy metals contamination of water is one of the environmental issue globally. Thus prepared fly ash–based zeolite (FZA)–supported nano zerovalent iron and nickel (nZVI/Ni@FZA) bimetallic composite from low-cost fly ash waste for the potential treatment of anion (Cr(VI) and cation Cu(II)) heavy metals from industrial effluents at pH 3 and 5, respectively in this study. The systematic interaction between FZA and nZVI/Ni and the adsorptive removal mechanism was studied. The mean surface area of the nZVI/Ni@FZA (154.11 m2/g) was much greater than that of the FZA (46.6 m2/g) and nZVI (4.76 m2/g) independently, as determined by BET-N2 measurements. The effect of influence factors on the removal of Cr(VI) and Cu(II) by nZVI/Ni@FZA, such as pH effect, initial concentration effect, time effect, temperature effect, coexisting metals, and ionic strength, and cumulative loading ability, were discussed. The maximum adsorption capacity of nZVI/Ni@FZA was 48.31 mg/g and 147.06 mg/g towards Cr(VI) and Cu(II), respectively. These were higher than those of nZVI@FZA and FZA. It demonstrated that Ni could play an important role in enhancing the reduction ability of nZVI. Furthermore, isothermal and kinetic results revealed that both heavy metal adsorption processes were rate limiting monolayer Langmuir adsorption on homogeneous surfaces. Thermodynamic results suggested that the adsorptive removal of metal ions was endothermic with spontaneity. The applicability of nZVI/Ni@FZA on real industrial wastewater treatment results demonstrate that the concentration of heavy metals were removed under the acceptable standard levels. Further the adsorption capacity of nZVI/Ni@FZA was higher than the nZVI@FZA and FZA. The overall results demonstrated that nZVI/Ni@FZA was a promising, efficient, and economically feasible sorbent for potential wastewater treatment. Moreover this is first report on the preparation nZVI/Ni@FZA bimetallic composite.

Heavy metal contamination in water and fish of the Hunza River and its tributaries in Gilgit–Baltistan: Evaluation of potential risks and provenance

This study focused on heavy metal (HM) in the water and fish of the Hunza River and its tributaries, located in Gilgit–Baltistan, Pakistan. Water and fish samples were collected and the concentrations of Cd, Ni, Co, Fe, Pb, Cr, Cu, and Zn were analyzed. The maximum HM concentration observed was 87.2 μ g/L for Fe in water at the Kohistan Block (downstream); the minimum HM value was found for Cd at 1.02 μ g/L from the Karakoram Block (midstream). Physicochemical parameters (basic parameters, anions, and HM) were observed to be within the drinking water guidelines set by the World Health Organization, except for Ni. Most physicochemical parameters showed an increasing trend from the Wakhan Block (upstream) to downstream. The concentration of HM in water and fish muscle was analyzed to evaluate potential health risks including chronic daily ingestion (CDI) and hazard quotient (HQ). Children showed the highest CDI of 53.2 μ g/kg-day of Fe through water intake and 48.1 μ g/kg-day of Ni via fish consumption. The HQ values of HM through water and fish consumption were <1. Provenance analyses of HM suggest that geogenic sources were the main source of water contamination.

Heavy metal contamination of water, soil and vegetables in urban streams in Machakos municipality, Kenya

Pollution of the environment by heavy metals emanating from rapid economic growth and improper waste and effluent disposal is a major concern. In this study, heavy metal concentrations (Cd, Cu, Pb, Zn and Cr) in vegetables, soil and water in two urban streams in Machakos municipality were analyzed. Physicochemical parameters; pH, temperature, total dissolved solids (TDS) and electrical conductivity (EC) were also measured on-site. One-way Analysis of variance (ANOVA) was used to test for the significant difference (p ≤ 0.05) of heavy metal concentrations in the vegetables, soil, and water across the different sampling sites. The relationship between the heavy metals in the soil, water and vegetables was investigated using Pearson correlation. Temperature (21.58 – 23.05 °C), pH (7.5 – 8.45) and TDS (577.5 – 865.83 mg/L) mean values were found to be within WHO acceptable limits for surface water while EC (864 – 1778.5 µS/cm) exceeded the set limits. Results showed that the mean concentrations (mg/kg) of Cd (BDL – 0.0011), Cu (0.0034 – 0.0055), Pb (0.0012 – 0.007), Zn (0.0232 - 0.1351), and Cr (0.0036 - 0.0292) in water and Cd (0.0058 - 0.0534), Cu (10.39 – 27.5), Pb (4.23 - 8.35), Zn (20.1 – 28.8) and Cr (8.17 – 10.03) in soil were within WHO permissible limits. Mean concentration values of (Zn (9.05 – 11.8), Pb (0.28 – 0.636), Cr (BDL – 1.002)) in spinach exceeded WHO permissible limits while Cd (BDL – 0.1285) and Cu (3.07 – 14.5) were within recommended levels. Cd (0.004 – 0.243), Cu (0.909 – 3.60) and Pb (BDL – 0.458) concentration levels in kale were within WHO safe limits for human consumption while Zn (12.06 – 18.8) and Cr (BDL – 1.62) exceeded WHO set limits. Presence of heavy metals (Zn, Pb, Cr) in the vegetables signifies a health risk hazard from consumption of these vegetables. Continuous monitoring of heavy metals in stream water, soil and vegetables is critical towards safeguarding public health.

Status of Heavy Metals Contamination in Water from Edagberi Creek, Engenni, Rivers State, South-South, Nigeria

The continuous monitoring of any aquatic medium is very important in the evaluation, management and legislative process for the renewal, restoration, safety and protection of the aquatic environment...

Heavy metal contamination in water, sediments and Planiliza subviridis tissue in the Donan River, Indonesia

Heavy metals like cadmium (Cd) and lead (Pb) are pollutants that are toxic, difficult to decompose and accumulate in biota. One of the biota that lives in the waters is mullet fish. This fish is demersal, has a relatively long life period, has a specific tolerance to the aquatic environment and highly consumable in Indonesia. Therefore need to know the metal content of Cd and Pb in water, sediments and mullet fish and their relationship in Indonesia. The study used a survey method with purposive random sampling at four stations, three replications. The study was conducted from June to November 2019. Analysis of data was descriptive, F-test and correlation. The results showed that the heavy metal content of Cd and Pb between stations in the water media, sediment and in mullet fish there was a significant difference. The highest Cd and Pb were showed in station III, coming from the oil industry, domestic waste and transportation activities. The heavy metal content of Cd and Pb in water, sediment and mullet fish (Planiliza subviridis) in the Donan River, Cilacap shows results exceeding the allowed threshold and danger to human health.

Improved toxicity analysis of heavy metal-contaminated water via a novel fermentative bacteria-based test kit

The objective of this study was development of a simple and reliable microbial toxicity test based on fermentative bacteria to assess heavy metal (Hg2+, Cu2+, Cr6+, Ni2+, As5+, or Pb2+)-contaminated water. The dominant species of test organisms used in this study was a spore-forming fermentative bacterium, Clostridium guangxiense. Toxicity of water was assessed based on inhibition of fermentative gas production of the test organisms, which was analyzed via a syringe method. Overall, the fermentative bacteria-based test kits satisfactorily identified increased toxicity of water as water was contaminated with high amounts of heavy metals; however, levels of inhibition were dissimilar depending on the species of metals. Inhibitory effects of Hg2+, Cu2+, Cr6+, and Ni2+ were considerably greater than those of As5+ and Pb2+. The 24 h half-maximum effective concentrations (EC50) for Hg2+, Cu2+, Cr6+, Ni2+, As5+, and Pb2+ were analyzed to be 0.10, 0.51, 1.09, 3.61, 101.33, and 243.45 mg/L, respectively, confirming that Hg2+, Cu2+, Cr6+, and Ni2+ are more toxic to fermentative gas production than As5+ and Pb2+. The fermentative bacteria-based toxicity test represents an improvement over other existing toxicity tests because of ease of end-point measurement, high reproducibility, and favorable on-site field applicability. These advantages make the fermentative bacteria-based test suitable for simple and reliable toxicity screening for heavy metal-contaminated water.

Ecofriendly Approach for Treatment of Heavy-Metal-Contaminated Water Using Activated Carbon of Kernel Shell of Oil Palm.

Heavy metal ion contamination in water poses a significant risk to human health as well as to the environment. Millions of tons of agricultural wastes are produced from oil palm plantations which are challenging to manage. In this study, we converted palm kernel shells (PKS) from a palm oil plantation into activated carbon (AC) having a surface area of 1099 m2/g using phosphoric acid as an activator. The prepared material was characterized using BET, XRD, Raman, FESEM and FTIR analyses. The AC was applied for the treatment of heavy-metal-contaminated water, and different parameters; the pH, adsorbent dosage, contact time and metal ion concentrations were varied to determine the optimal conditions for the metal ion adsorption. Different kinetic models; the zeroth, first-order and second-order, and Freundlich and Langmuir isotherm models were used to determine the mechanism of metal ion adsorption by the AC. Under the optimized conditions, Cr6+ and Pb2+ were removed completely, while Zn2+ and Cd2+ were more than 80% removed. This is a greener approach in which an agricultural waste, PKS is converted into a useful product, activated carbon and subsequently applied for the treatment of heavy metal-contaminated water.

Heavy metal contamination in water, sediments, and fauna of selected areas along the Kenyan coastline

Abstract. Mwatsahu SH, Wanjau R, Tole M, Munga D. 2020. Heavy metal contamination in water, sediments, and fauna of selected areas along the Kenyan coastline. Ocean Life 4: 37-47. Every year millions of tons of industrial waste and municipal sewage are dumped into the world’s oceans as rivers carrying agricultural wastes discharge their waters into the ocean. The Mombasa inshore (Kilindini and Portreiz) waters and Sabaki/Malindi bay, Kenyan coastline, complex are characterized by rapid urbanization and industrial activities, including shipping, agriculture, and tourism. As a result, the coastal fauna, sediments, and seawater are polluted with heavy metals, raw sewage, and organochlorine pesticides. Heavy metals such as Cadmium (Cd), Copper (Cu), Chromium (Cr), Lead (Pb), Iron (Fe), Manganese (Mn), Mercury (Hg), and Zinc (Zn) have threshold limits (USEPA) above which they are toxic. The aim of this study was to assess the levels of heavy metals Cd, Cu, Cr, Fe, Mn, Hg, and Zn in selected areas along the Kenyan Coastline. The analysis was done during the dry and wet seasons. The levels of the heavy metals were determined using Atomic Absorption spectro-photometry flameless Atomic Absorption Spectrophotometry (Mercury cold vapor), and Energy Dispersive X-ray fluorescence. The levels of the metals were as follows: In sediments, Hg: nd, Cr: nd, Cu: 9.912-40.412 µg/g, Fe: 3,195.667-35,435.981 µg/g, Mn: 135.467-228.780 µg/g, Zn: 54.700 -181.725 µg/g. Biota: Hg: nd, Cr: nd, Cu: 43.963-229843 µg/g, Mn: 29.770-486.611 µg/g, Fe: 379.853-35,277.752 µg/g, Zn: 99.476-872.852 µg/g, Cd: nd, Pb: 135.407-833.111 µg/g. Sea water: Cr: 0.015-0.026 µg/mL, Fe: 0.062-16.524 µg/mL, Cu: 0.010-0.033 µg/mL, Zn: 0.028-0.066 µg/mL, Pb: 0.006-0.010 µg/mL. Cd and Hg levels were not detected in seawater, sediments, and fauna. In contrast, Cr was not detected in sediments and fauna but had levels above USEPA guidelines at Kilindini, Malindi Bay, and Sabaki estuary sites. Cu had levels above USEPA guidelines at Sabaki in the water and sediments at most sites. Pb levels were above USEPA guidelines at most sites of the Kenyan Coastline, while Zn levels indicated moderate pollution in seawater, sediments, and fauna. These findings indicated that seawater sediments and fauna from the Kenyan Coastline are moderately polluted with Cu, Pb, and Zn according to USEPA guidelines. It is recommended that regular assessments of pollution levels be done and measures put in place to prevent increased pollution of the Kenyan Coastline.

Developing a highly selective method for preconcentration and determination of cobalt in water and nut samples using 1-(2-pyridylazo)-2-naphthol and UV-visible spectroscopy.

Heavy metal contamination in water and agricultural products is a major concern that causes risks for human health. This article describes a highly selective approach to preconcentrate cobalt(II) (Co(II)) ions based on the standard UV-visible measurement of Co(II)-1-(2-pyridylazo)-2-naphthol complex at λ = 628 nm in water and nut samples. In this method, magnetic silica (mSiO2 ) was utilized as a practical sorbent and 1-(2-pyridylazo)-2-naphthol was employed as a complexing agent in the elution step. The adsorbent was characterized via X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy. The effects of the main variables (pH, adsorption time, sorbent amount, pH of eluent, ligand volume, and desorption time) were investigated and established. The maximum recovery was achieved at pH 7 ± 0.3, adsorption time of 60 min, sorbent amount of 40 mg, eluent pH 8 ± 0.2, ligand volume of 2 mL (16.95 × 10-4 mol L-1 ) and desorption time of 30 min. The linearity of dynamic range (10-500 μg L-1 ), limit of detection (0.32 μg L-1 ), relative standard deviation (3.04%), and preconcentration factor (25) show the reliability of the method. The sorbent was reusable 12 times. Selectivity and the effect of interference ions were successfully examined. The adsorption process of Co(II) ions on mSiO2 was investigated based on Langmuir and Freundlich isotherms. The Freundlich model was fitted with the system and the maximum capacity adsorption of mSiO2 for Co(II) adsorption is 2.35 mg g-1 . Then, the kinetics study revealed that the adsorption process of Co(II) ions on the mSiO2 follows the pseudo-first-order model. The thermodynamics parameters ΔG, ΔS, and ΔH were calculated. The method was fruitfully applied to preconcentrate Co(II) ions in water and nut samples. This method offers high selectivity and precision for determining Co(II) ions. © 2020 Society of Chemical Industry.

Cadmium removal from aqueous medium by jute stick activated carbon using response surface methodology: factor optimisation, equilibrium, and regeneration

ABSTRACT Heavy metal contamination of water is a burning global issue, and enormous importance has been given on easily applicable watertreatment methods namely adsorption. However, search for an efficient and reusable adsorbent is ever-evolving. In this study, activated carbon from highly ligno-cellulosic jute stick (JS-AC), the agricultural by-product of jute (Corchorus olitorius), was evaluated as a new adsorbent for removing cadmium (Cd) from the aqueous medium. The direct and interaction effects of four independent adsorption factors namely, initial Cd(II) concentration (20–100 mg/L), adsorbent dose (0.5–1 g/L), solution pH (3–7), and time (30–180 min) were investigated by applying response surface methodology (RSM). A 24 Box-Behnken matrix model with 3 centre points indicated that the maximum % Cd(II) removal was achieved at the initial concentration, dose, pH and time of 60.87 mg/L, 0.5 g/L, 7, and 30 min, respectively. The adsorption equilibrium was investigated by applying Freundlich, Langmuir, Temkin, and Jovanoic isotherm models while Langmuir isotherm exhibited the best fit (R2 = 0.99). The maximum Cd(II) adsorption capacity value of JS-AC was 73.53 mg/g. Finally, JS-AC was regenerated with 0.1M HNO3 as the desorption medium and reused for five successive cycles. This study indicated that jute stick, the under-utilised agro-residue of a cash crop, could be converted into a valuable product like JS-AC which offers immense application potential as an efficient and reusable adsorbent to treat Cd(II) contaminated aqueous medium before releasing in the environment.