Heavy Metal Removal Capacity Research Articles

Ultrasound Activated Clay: Preliminary Study of PB And as Removal in Aqueous Media

Objective: The objective of this study was to evaluate the removal of Pb and As in aqueous media by activated clay (AC). Theoretical Framework: Heavy metals in water represent a risk to health and ecosystems, their removal through new materials is a challenge for the industry. Method: The methodology adopted for this research comprises in that natural clay (NC) was activated with sodium chloride and phosphoric acid followed by sonication. A synthetic solution of Pb and As was prepared at different pH. Results and Discussion: The zero charge point was found to be 7.10 for AC and 8.02 for NC, the ζ potential was found to be between - 41.15 and - 45.43 mV in the pH range of 4 to 12, with degree of crystallinity of 97.24% and crystal size of 2.85 nm determined by XRD. FTIR analysis allowed the identification of functional groups with chelating capacity. Was observed As removal of 75.51% (110.40 mg/g) and 23.23% (58.13 mg/g) and 97.75% (106.41 mg/g) and 100.0% (206.53 mg/g) for Pb with AC and NC respectively at pH 6 and 8. Research Implications: Los reaultadoe encontrados sugieren que la arcilla activada se convierte en un material alta capacidad de adsorción de metales pesados en sistemas multimetal. Esta cualidad se debe al incremtno de grupos funionales en su superficie y al tamaño nanométrico que incrementa el área de contacto. Originality/Value: Activation of the clay with sodium chloride and weak acid followed by sonication is an environmentally friendly process that produces a material with high heavy metal removal capacity in aqueous media.

Designing a biochar-based pretreatment method for distillery effluents entering constructed wetlands

Spent lees is an important distillation waste by-product created during whisky production, characterised by low pH and high dissolved copper (dissCu) content. Constructed wetland systems (CWs) are used in some Scotch whisky distilleries to treat spent lees prior to surface water discharge to prevent substantial environmental risks of spent lees in aquatic ecosystems, by buffering the acidic nature and decreasing the dissCu and organics content. However, as these wetland systems are biological communities (containing bacteria, fungi, plants, etc.), direct disposal of spent lees into CW ecosystems presents a challenge given its nature. This study investigates the efficacy of modified biochar (waste) sourced from whisky cask cooperage operations, as an effluent pretreatment method. The aim is to transform this raw biochar into NaOH-modified biochar, which will be capable of buffering the effluent pH and removing dissCu from spent lees before it enters CWs. To enhance raw biochar, NaOH modification and additional heat treatment were utilised which increased the alkalinity, heavy metal removal capacity and pH buffering potential. Experiments with 0.2% and 2% NaOH treated biochar demonstrated its treatment performance using a diverse range of spent lees samples with varying characteristics, including pH (4.1–4.4), dissCu concentrations (33.8–59.5 mg/L), and total organic carbon (685–754 mg/L). Column studies further supported the efficacy of the modified biochars, showing significant pH elevation and efficient dissCu removal (of 5.72 mg of Cu per g of biochar) when treating spent lees. This dissCu removal capacity compares favorably with other wood-derived biochars studied in the literature, which have reported between 2.75 and 7.44 mg/g. Surface characterisation techniques (EDX, XPS, FTIR, XRD) showed how the Cu ions microprecipitated on the modified biochar surface, validating its remediation potential. This study highlights the potential of biochar as a sustainable pretreatment solution for distillery effluents, paving the way for enhanced and more circular waste management practices within the Scotch whisky industry.

Effect of eco-friendly pervious concrete pavement with travertine waste and sand on the heavy metal removal and runoff reduction performance

To address the negative environmental and economic impact of the large amounts of solid waste generated during travertine mining and to reduce the dependence on natural aggregates and cement for pervious concrete pavement applications, travertine waste, as aggregate and powder, was used for the travertine powder pervious concrete (TPPC) to improve the utilization of solid waste and decrease CO2 emissions. The experimental results showed that using 25% travertine aggregate and 5% powder results in a compressive strength reduction of only 9.8% to 25.92 MPa but a significant improvement in water permeability of 57.1% from 3.89 to 6.11 mm/s. To improve the performance of TPPC, further research was done on the effect of sand addition rate (SAR) on TPPC's density, compressive strength, porosity, water permeability, freeze-thaw resistance and heavy metal removal capacity to obtain an optimal incorporation ratio. As SAR rises, the compressive strength of TPPC with sand (STPC) initially increases and then decreases, while permeability behaves inversely. At 3% SAR, the compressive strength reached a maximum of 26.51 MPa, primarily due to the sand added to fill in some of the pores and stabilize the gradation. After 25 cycles, the strength loss rate of STPC varies from 11.39 to 17.93% and the freeze-thaw resistance is most excellent when SAR is 3%. The removal rate of heavy metals using the immersion method was found to be significantly higher (83.4–100%) compared to the rapid method (11.7–28.1%). Therefore, the 3% SAR was recommended for the mixture design of STPC. A laboratory-scale version of the pavement was constructed to assess the efficacy of STPC pavement (STPCP) in reducing runoff and removing heavy metals. The results showed that STPCP could remove more than 94% of runoff with varying intensities after 1 h. The STPCP exhibited removal rates ranging from 42.0 to 99.4% for Cd2+ and 79.5–95.4% for Cu2+. STPCP also attained a removal rate above 98% for Pb2+ after 30 min, demonstrating its environmental friendliness.

Bioremedial Capacity of Indigenous Hydrophytes and Microalgae of Bangladesh: A Comparative Study on their Potential in Tannery Effluent Treatment

Aims: This study aimed to identify the bio-remedial potential of indigenous hydrophytes (Salvinia cucullata and Lemna minor) and microalgae (Spirulina platensis) of Bangladesh for treatment of tannery wastewater disposed in the open environment. Study Design: The capacity of improving the water quality of the tannery effluent by bioremediation was assessed. The quantitative determination included the comparison of physical characters (pH, TDS, EC, DO, COD) and heavy metal profile (Pb, Cr, Cu, Zn) of the tannery effluent before and after treatment. Effluent treatment was carried out by individual species separately and in combination with all for a total of 25 days. Place and Duration of Study: Major experiments were carried out at the Applied Botany Laboratory, Dhaka Laboratory, BCSIR, Dhaka, Bangladesh from January 2022 to February 2024. Quantitative estimations were carried out at Soil & Water Laboratory, Dhaka Laboratory, BCSIR, Dhaka, Bangladesh. Methodology: The tannery effluent was characterized by means of physiochemical parameters and heavy metal concentration prior to the experimental procedure. Four treatment plans were designed, three treatments (TSC, TLM, TSP) using individual species separately and one treatment (TC) using all three species in combination. The treatment continued for 25.0 days. The physiochemical parameters of the treated effluent were measured at 5.0-day intervals and heavy metal conc. Were measured on the 0th, 10th, and 25th days of the experiment. Comparative analysis of the data was utilized to determine useful species for further applied studies in future. Results: After treatments, a reduction at TDS level down to 3230 from 5150 mg/L, and an EC dropdown to 3290 from 10340 μS/cm was observed. Heavy metals removal capacity of the tested species was found as follows, S. cucullata: Zn > Cr >Pb> Cu, L. minor: Pb> Cr > Cu > Zn, S. platensis: Cu > Zn >Pb> Cr, and the combination treatment: Pb> Cu > Zn > Cr. The observation showed high efficiency of S. platensis in TDS reduction and Zn absorption, L. minor in COD reduction and Pb absorption, and S.cucullata in Zn absorption. Conclusion: The comparative data suggested the overall improvement of the effluent quality can be achieved by a combined treatment of L. minor and S. platensis, quickly and cost-efficiently. Further investigation is required for an in-depth understanding of their combined potential. Additionally, investigation will be carried out on their potential in Arsenic (As) removal and nano-particle production from post-treatment biomass.

Removing heavy metal ions from wastewater by Chlorella sorokiniana coupled to manganese-doped magnetic ferrite nanoparticles

In this study, we investigated the benefit of combining Chlorella sorokiniana with manganese-containing ferrite nanoparticles (NPs) for heavy metal removal and cell harvesting. Our results demonstrate that the combination of non-toxic nanoparticles significantly enhances the heavy metal removal capacity of C. sorokiniana without affecting its growth. The microalgae combined with NPs was able to sequester Cr6+, Co2+, and Ni2+ from aqueous solutions and could remove these metals at a higher adsorption capacity and within a relatively short time than their individual counterparts, indicating a synergistic effect between the algal cells and the nanomaterials, where bioadsorption and chemisorption were the main players. Both biosorption and chemisorption capacities were found to be the highest for single-metal systems and decreased when coexisting ions were present in the solution. The adsorption of the heavy metals evaluated was better described by the pseudo-second order model than the pseudo-first order model, indicating that chemisorption dominated over physisorption. These characteristics suggest that the combination of biosorbents with nanosorbents is a promising approach for the treatment of water contaminated with heavy metals making this process more efficient, economical, sustainable, and clean.

Heavy Metals Removal Using Nano‐Hydroxyapatite Extracted from Cattle Bones

AbstractLocal cattle (lamb and camel) bones were used as a starting material to obtain pure nano‐hydroxyapatite n‐HAp. Extraction of nano‐HAp is done at 700 °C and 900 °C calcination temperatures, followed by some characterization technics such as FTIR spectroscopy, UV‐visible spectroscopy, XRD diffraction pattern, SEM and EDX analyzes. All the technics used have confirmed that calcination at these temperatures leads to a material in which pure hydroxyapatite is the only crystallographic phase. The heavy metals removal capacity of n‐HAp applied to Cu2+ and Co2+ from aqueous solutions was exanimated and compared. The obtained results were interpreted and compared based on; (i) the calcination temperature, (ii) the nature of the adsorbed cation on the nano‐hydroxyapatite surface and (iii) the nature of the adsorbent.

Screening the heavy metal removal capacity of magnetically modified fungal biosorbent

Screening the heavy metal removal capacity of magnetically modified fungal biosorbent

Nano Modifications of Biochar to Enhance Heavy Metal Adsorption from Wastewaters: A Review.

Biochar (BC) is a carbon-rich material that can be obtained by thermal decomposition of agricultural solid waste under oxygen-limited conditions. It has received increasing attention as a cost-effective sorbent to treat metal-contaminated water due to attributes such as high porosity and the presence of various functional groups. The heavy metal (HM) sorption and removal capacity of BC can be enhanced by developing novel biochar nanohybrids (BNHs) that can be produced via surface modification of BC with nanomaterials. Loading of nanomaterials on the biochar surface can improve its physicochemical properties through alterations in the functional group profile, porosity, and availability of active sites on the BC surface which can enhance the HM adsorption ability. This manuscript provides information on preparation of nano-based biochar hybrids emanating from the type of modifying agent for the removal of different HM ions from wastewaters, and the underlying mechanisms have been discussed. Further, this compilation discusses published literature depicting the influence of different processes of preparation on the physicochemical properties and adsorption capacity of nanobiochar hybrids. The potential risks of BNHs have been reviewed to effectively avoid the possible harmful impacts on the environment, and future research directions have been proposed.

Enhanced removal of heavy metals by α-FeOOH incorporated carboxylated cellulose nanocrystal: synergistic effect and removal mechanism.

Simultaneous and highly efficient removal of heavy metal cations and oxyanions is significant for both water and soil remediation, but it remains a major challenge due to the complexity. In this work, a novel hybrid of α-FeOOH incorporated carboxylated cellulose nanocrystal (Fe/CNC) is synthesized via a hydrothermal process, which shows improved α-FeOOH dispersion and heavy metal removal capacity. In single adsorbate system, maximum adsorption capacities toward Pb(II), Cd(II), and As(V) by Fe/CNC reach 126.06, 53.07, and 15.80mgg-1, respectively, and the Fe leaching is much lower than that of α-FeOOH. In binary and ternary adsorption systems, simultaneous removal of Pb(II), Cd(II), and As(V) is proved, and the competition and synergy coexist among heavy metals. FTIR and XPS spectra have revealed the synergistic removal mechanism: Pb(II) and Cd(II) are mainly removed by surface complexation with oxygen-containing functional groups on C-CNC and α-FeOOH, and precipitation on the surface of α-FeOOH, while ligand exchange with Fe-OH is responsible for As(V) removal. The soil incubation experiments show that exchangeable and carbonate-bound Pb, Cd, and As are transformed into more stable forms in contaminated soil containing Fe/CNC composites. This work provides a novel composite material for remediation of heavy metal-contaminated environments.

Continuous Systems Bioremediation of Wastewaters Loaded with Heavy Metals Using Microorganisms

Heavy metal pollution is a serious concern of the modern era due to its widespread negative effects on human health and to the environment. Conventional technologies applied for the uptake of this category of persistent pollutants are complex, often expensive, and inefficient at low metal concentrations. In the last few years, non-conventional alternatives have been studied in search of better solutions in terms of costs and sustainability. Microbial adsorbents are one of the biomass-based sorbents that have extensively demonstrated excellent heavy metals removal capacity even at low concentrations. However, most of the carried-out research regarding their application in wastewater treatment has been performed in discontinuous systems. The use of microorganisms for the uptake of metal ions in continuous systems could be an important step for the upscale of the remediation processes since it facilitates a faster remediation of higher quantities of wastewaters loaded with heavy metals, in comparison with batch systems removal. Thus, the current research aims to analyze the available studies focusing on the removal of metal ions from wastewaters using microorganisms, in continuous systems, with a focus on obtained performances, optimized experimental conditions, and the sustainability of the bioremoval process. The present work found that microbial-based remediation processes have demonstrated very good performances in continuous systems. Further sustainability analyses are required in order to apply the bioremediation technology in an optimized environmentally friendly way in large-scale facilities.

Potential removal capacity and secondary pollution risk evaluation of heavy metals in Gracilaria lemaneiformis from a typical seaweed farming base

Seaweeds are significant primary producers in marine ecosystems and accumulate heavy metals from the environment during growth. However, seaweed litter is produced during the growth and harvest process and has become an important bottleneck that restricts the sustainable development of the seaweed cultivation industry. In this study, we investigated the risk assessment and potential removal of heavy metals in the Gracilaria lemaneiformis cultivation zone in a typical seaweed farming base and evaluated the secondary pollution risk of heavy metals in G. lemaneiformis litter. The results indicated that G. lemaneiformis was a good candidate for the removal and active absorption of heavy metals. A total of 60 thousand tons of harvestable G. lemaneiformis was estimated to remove 242.5 kg copper, 34.5 kg cadmium, 74 kg lead, and 2134.5 kg zinc from a typical seaweed farming base in 2018. Furthermore, the G. lemaneiformis did not pose a health risk to consumers. Variations in the heavy metal accumulation index between dead and fresh G. lemaneiformis litter differed significantly and provided evidence that metals could be either imported or exported from litter to the environment. It is suggested that G. lemaneiformis litter had a potential function in simultaneous heavy metal accumulation and release, and the function of metal accumulation was more effective during growth and decay. The results of this study contribute to the knowledge of heavy metal pollution status and risk assessment in the environment and in G. lemaneiformis, underscoring the strong capacity of heavy metal accumulation in G. lemaneiformis from the environment and the potential heavy metal removal by G. lemaneiformis cultivation and its utilization in a typical seaweed farming base.

Chitosan Functionalized with Carboxyl Groups as a Recyclable Biomaterial for the Adsorption of Cu (II) and Zn (II) Ions in Aqueous Media.

The modification of chitosan represents a challenging task in obtaining biopolymeric materials with enhanced removal capacity for heavy metals. In the present work, the adsorption characteristics of chitosan modified with carboxyl groups (CTS-CAA) towards copper (II) and zinc (II) ions have been tested. The efficacy of the synthesis of CTS-CAA has been evaluated by studying various properties of the modified chitosan. Specifically, the functionalized chitosan has been characterized by using several techniques, including thermal analyses (differential scanning calorimetry and thermogravimetry), spectroscopies (FT-IR, XRD), elemental analysis, and scanning electron microscopy. The kinetics and the adsorption isotherms of CTS-CAA towards both Cu (II) and Zn (II) have been determined in the aqueous solvent under variable pH. The obtained results have been analyzed by using different adsorption models. In addition, the experiments have been conducted at variable temperatures to explore the thermodynamics of the adsorption process. The regeneration of CTS-CAA has been investigated by studying the desorption process using different eluents. This paper reports an efficient protocol to synthesize chitosan-based material perspective as regenerative adsorbents for heavy metals.

Nano-Clay and Iron Impregnated Clay Nanocomposite for Cu2+ and Pb2+ Ions Removal from Aqueous Solutions

Several physicochemical techniques have been widely studied for heavy metals removal despite most of them are associated with challenges of higher cost, accessibility, and complex technical feasibility. In this study, nano-sorbent materials were developed from a naturally available clay matrices and its heavy metals (Cu2+ and Pb2+) removal capacity was tested at its pristine and iron impregnated form. Both top to down and borohydride reduction methods were used to produce the nano-sorbents. The nano-sorbents were characterized by XRD, XRF, SEM, FTIR, BET, and TGA/DGA. The sorption was studied in batch experiments. The surface area, pore-volume, and pore diameter of nano-clay were found 43.49 m2/g, 0.104 cm3/g, and 2.81 nm, respectively while iron impregnated nano-clay has shown a surface area (73.11 m2/g), pore-volume (0.153 m3/g), and pore diameter (3.83 nm). Both nanoparticles have shown a mesoporous nature. The highest Cu2+ and Pb2+ removal capacity of nano-clay was 99.2% (~11.9 mg/g) and 99.6% (~11.95 mg/g), respectively. Whereas, the iron impregnated nano-clay has achieved the highest Cu2+ and Pb2+ removal efficiency 99.8% (~11.97 mg/g) and 99.7% (11.96 mg/g), respectively. The highest Cu2+ adsorption efficiency of iron impregnated nanoclay was achieved at pH 5.0, adsorbent dose 0.83 g/L, contact time 150 minutes, and Cu2+ initial concentration 4 ppm while its highest Pb2+ adsorption activity was achieved at pH 5.0, contact time (90 minutes), Pb2+ initial concentration (6 ppm), and the adsorbent dose (0.67 g/L). Whereas, the Cu2+ adsorption using nano-clay was highest at pH 5.0, contact time (180 minutes), adsorbent dose (1.0 g/L), and Cu2+ initial concentration (2 ppm). While, pH 5.0, contact time (90 minutes), adsorbent dose (0.83 g/L), and Pb2+ initial concentration (4 ppm) was found to the conditions of highest Pb2+ removal. In all cases, the pseudo-second-order kinetics indicated the presence of chemisorption. Langmuir adsorption characteristics has been reflected on Pb2+ and Cu2+ removal activities of the nanoclay and iron impregnated nanoclay, respectively. Whereas, Freundlich isotherm model was better fitted for Cu2+ adsorption activity of the nanoclay. The −ΔG (<−20 KJ/mol), + ΔH°, and + ΔS° have shown a spontaneous and endothermic adsorption activity with a high level of adsorbents disorder. In general, the result of iron impregnated nano-clay has shown a promising result for the removal of Cu2+ and Pb2+ aqueous solution.

Application of the Biomass from the Shell of Pachyrhizus erosus in the Removal of Hexavalent Chromium from Contaminated Waters

Aims: Recently, the removal capacity of different heavy metals from sites contaminated by low-cost materials has been studied, with promising results. These adsorbents include dead microorganisms, clay minerals, agricultural waste, industrial waste, and other materials. The objective of this work was studying the removal capacity of Chromium (VI) by the biomass of the shell of Pachyrhizus erosus, by the Diphenylcarbazide colorimetric method.
 Place and Duration of Study: Sample: Faculty of Chemical Sciences. Autonomous University of San Luís Potosí, S.L.P., between July and November 2021.
 Methodology: The biomass was obtained from the shell of P. erosus, acquired in the Republic market of the city of San Luís Potosí, during the month of July 2021. For obtain the biomass, the shell was washed during 24 hours in EDTA at 10% (p/v), and 1 week with tridesionized water under constant stirring, with water changes every 12 hours, and we work with 100 mL of a 100 mg/L solution of Chromium (VI) obtained by diluting a 1 g/L standard solution prepared in tridesionized water from K2Cr2O7. The pH of the solution was adjusted with 1 M H2SO4 and/or 1 M NaOH, before adding it to the biomass.
 Results: The highest bioadsorption was at 7 hours, at pH 1.0 and 28°C. Regarding temperature, the highest removal was at 60°C and 1.5 hours, with a removal of 90.69%. At the metal concentrations analyzed, the natural biomass showed a good removal capacity, in addition too efficiently removal the metal in situ (93.6% of contaminated water), at 3 days of incubation, with 5 g of biomass, and 100% of removal from contaminated earth, at 52 hours of incubation, with 5 g of biomass).
 Conclusion: Therefore, this biomass can be used to remove it from industrial wastewater and contaminated earth.

The Use of the Biomass of a Macromycete Fungus for the Bioremediation of Chromium (VI) in Solution

Recently, the removal capacity of different heavy metals from sites contaminated by low-cost materials has been studied, with promising results. These adsorbents include dead microorganisms, clay minerals, agricultural waste, industrial waste, and other materials. The objective of this work was studying the removal capacity of Cr (VI) by a commercial mushroom, the macromycete Agaricus bisporus (white strain), by the Diphenylcarbazide colorimetric method It was found that the biomass removal 100 mg/L of the metal at 21 minutes, pH 1.0, 28oC, and 100 rpm. On the other hand, if the concentration of the metal is increased, the removal capacity for the analyzed biomass decreases at 28oC. 200 mg/L are removal at 60 minutes, while with 1 g/L of the metal, its removal 90.3%. If the concentration of the bioadsorbent is increased, the removal of the metal also increases, and the presence of other heavy metals does not influence in the removal of the metal, and this was desorbed 70.4%, with NaOH 0.5 N. Finally, it was observing that after 7 days of incubation, 76.2%, and 66.1%, of Cr (VI) present in naturally contaminated earth and water, were removal, respectively.

Effect of Pyrolysis Temperature on Copper Aqueous Removal Capability of Biochar Derived from the Kelp Macrocystis pyrifera

Seaweed biochar is an efficient alternative bioadsorbent for Cu2+ removal due to its low cost and heavy metal removal capacity. Using the slow pyrolysis process, we produced biochars from Macrocystis pyrifera at 300 (BC300), 450 (BC450), and 600 °C (BC600). The physicochemical and structural properties of the biochar samples improved with increasing pyrolysis temperature from 300 to 450 °C, whereas no significant differences were observed with further increases in temperature to 600 °C. The yield ranged between 49% and 62% and had a high ash content (57.5–71.1%). BC450 and BC600 presented the highest surface areas and higher porosities. The FTIR spectra indicated that an increase of temperature decreased the acidic functional groups due to depolymerization and the dehydration processes, increasing the aromatic structures and the presence of calcium carbonate. The fittings of the kinetic models were different for the BCs: for the BC450 and BC600 samples, the Cu2+ adsorption was well-represented by a pseudo-first-order model; for BC300, a better fit was obtained with the pseudo-second-order model. The rate-limiting step of Cu2+ adsorption on BCs was represented by both models, liquid film diffusion and intraparticle diffusion, with surface diffusion being more important in BC300 and BC600, and intraparticle diffusion in BC450, in agreement with the pore size of the biochar samples. The adsorption isotherms of all BCs showed Langmuir behavior, representative of a chemisorption process, which was corroborated by the energy adsorption values determined by the D–R model. The maximum monolayer Cu2+ adsorption capacities were 93.55 and 58.0 mg g−1 for BC600 and BC450, respectively, whereas BC450 presented the highest affinity. Other mechanisms involved in controlling heavy metal removal from aqueous suspensions using these seaweed biochars remain to be explored. We conclude that BC450 and BC600 from M. pyrifera are the most efficient adsorbents for Cu2+ aqueous removal and are thus an appropriate alternative for bioremediation.

Purification Performance of Filtration Process for Pig Slurry Using Marine Sands, Silty Loam Soils, Fly Ash and Zeolite

Filtration is a simple ecological process for the treatment of effluents. This research examined the physicochemical properties of micronutrients, macronutrients, and heavy metals (HM) removed after the slow filtration of pig slurry (PS) through multiple media: sands, silt loam soils, fly ash, and zeolite. The objective was to find a new layer that can be added to our constructed wetland (CW) to improve its efficiency and study how the slurry reacts to these natural materials. The filtration achieved an approximate removal rate of 99.99% for total suspended solids (TSS) and nitrogen and 61, 94, 72, and 97%, respectively, for electrical conductivity (EC), turbidity, chemical oxygen demand (COD), and five-day biological oxygen demand (BOD5). The two sands, soil 1, and zeolite, had a macronutrient reduction median of 60%, whereas soil 2, 3, 4, and fly ash released macronutrients such as Na, Ca, and Mg. All the media achieved nearly 99.99% micronutrient removal for Fe and Zn. The Cu removal rate was over 86% except for sand 1 and 2 and soil 1, which reduced it to only 46%; the overall Mn removal rate was more than 80% except for soil 3 and soil 4, where it was only 9%. Zeolite had a 99.99% removal capacity for HM as opposed to sand 2, soil 4, and fly ash, which released some HMs (Ni, Cu). This inexpensive and abundant media filtration process is sound technically and financially sound and seems to be an ideal cost-efficient treatment for pig slurry.

Synthesis, characterization, and assessment of novel sulfonated polynorbornene dicarboximides as adsorbents for the removal of heavy metals from water.

The occurrence of heavy metals in the natural aquatic systems arising from anthropogenic sources is an issue of global and environmental concern because of their extremely harmful effects to living beings even in rather low concentrations. The synthesis and ring-opening metathesis polymerization (ROMP) of novel norbornene dicarboximides bearing highly aromatic pendant groups, specifically, N-4-tritylphenyl-norbornene-5,6-dicarboximide (2a) and N-2,4,6-(triphenyl)phenyl-norbornene-5,6-dicarboximide (2b), their hydrogenation and further polymer sulfonation to render them adsorbents for the uptake of heavy metal ions from water is reported in this study. The macromolecules were characterized by means of FT-IR, 1H NMR, and thermal analysis, among others. A thoroughly kinetic and isothermal study of adsorption in single and ternary aqueous solutions of Pb2+, Cd2+, and Ni2+ was performed considering several experimental variables for instance initial metal concentration, contact time and solution pH. In general, the experimental data were adjusted more efficiently to the pseudo-second order kinetic model and to the Freundlich isotherm model, respectively. The maximum removal amounts were found to be 55.7 mg/g for Pb2+, 33.9 mg/g for Cd2+, and 10.2 mg/g for Ni2+ in the sulfonated trityl-bearing polymer 5a while those found for the sulfonated triphenyl-bearing polymer 5b were 31.5 mg/g for Pb2+, 26.6 mg/g for Cd2+, and 7.0 mg/g for Ni2+, respectively. The higher heavy metal removal capacity of polymer 5a was attributed to its also higher degree of sulfonation. The outcomes indicate that these novel sulfonic acid containing polymer-based adsorbents are effective for the uptake of heavy metallic elements from water.

Heavy metal ions removal from wastewater using various low-cost agricultural wastes as adsorbents: a survey

Toxic heavy metals have an important role in water pollution. Because of their toxicity and non-biodegradability which affects humans, animals, and also plants. Researchers in the field of environment used various heavy metal removal methods, such as ion exchange, precipitation, evaporation, membrane filtration and adsorption. Low cost, high efficiency and easy regeneration make the adsorption process as an effective technique in the heavy metal removal. The purpose of this review is to gather sufficient information about various agricultural waste adsorbents and their removal capacity for heavy metals.

HEAVY METAL ADSORPTION FROM A MULTIMETAL SOLUTION BY BENTONITE-KAOLIN-ZEOLITE PELLETS: LINEAR AND NONLINEAR REGRESSION, AND ERROR ANALYSIS

Background: Heavy metal pollution has significant impacts on health and ecosystems; remediation technologies can reduce the cost to solve these problems. Heavy metals present a severe problem in the environment, mainly for their tendency to persist, bioaccumulate and biomagnification in the trophic chain. Removing these toxic compounds from wastewater remains a challenging task. Aim: Heavy metal removal capacity was analyzed using adsorbent pellets made with natural bentonite, kaolin, and zeolite. This study describes the equilibrium adsorption and kinetics of metal removal by using linear and nonlinear regression analysis. Adsorption mechanisms were also analyzed. Methods: The goodness of fit of the adsorption equilibrium data was tested with the four linearized forms of the Langmuir equation, as well as the Freundlich, Temkin, and Dubinin-Radushkevich models. To choose the best-fit model with greater reliability, five error functions were used: R2, X2, SSE, ABS, and ARE. For adsorption kinetics the Pseudo First Order, Pseudo Second Order and Elovich models were studied with linear and nonlinear regression analysis. Results and Discussion: Type I linearization of the Langmuir isotherm showed the best fit for the three metals, with maximum adsorption capacities for lead, copper, and cadmium of 7.27, 1.45 and 0.28 mg/L, respectively. The results show that Pseudo Second Order with linear regression best fitted for lead and copper data and Pseudo First Order model with linear regression for cadmium. Conclusions: Nonlinear regression was found better to fit adsorption equilibrium models and linear regression to fit kinetics models. The main mechanisms responsible for adsorption in the system are thought to be ion exchange between functional groups and cations and surface charge attraction related to Van der Waals forces.