Single and competitive adsorption affinity of heavy metals toward peanut shell-derived biochar and its mechanisms in aqueous systems

Converting peanut shells into biochar by pyrolysis was considered an environmentally friendly and efficient method for agricultural solid waste disposal.The properties of peanut shell-derived biochar(PBC)under different temperature and its adsorption capacity of heavy metals were investigated.It was found that PBC400 exhibited the highest cumulative capability for heavy metals elimination in single solute because of its high specific surface area and rich functional groups.Furthermore,the competitive adsorption revealed that PBC had a substantial difference in adsorption affinity from diverse heavy metal ions,sorption capacity decreased as Pb2+>Cu2+>Cd2+>Ni2+>Zn2+,which was lower than in a single solute.The adsorption process using selected biochar was optimized with respect to p H,reaction time,adsorbent dose,and initial concentration of heavy metals.The kinetic data was well fitted with PSO model,and the Langmuir model was adopted for adsorption equilibrium data in both cases of single solutes and mixed solutes for all heavy metals,which indicated that the removal course was primarily explained by monolayer adsorption,and chemical adsorption occupied an important role.Therefore,peanut shells derived biochar could be a potential and green adsorbent for wastewater treatment.

Removal of heavy metals from artificial metals contaminated water samples based on micelle-templated silica modified with pyoverdin I

The micelle-templated silica （MTS） was firstly chemically modified with 3-glycidoxypropyl-trimethoxysilane （GPTMS） before immobilized with pyoverdin I. The characteristics of pyoverdin I-anchored onto the modified MTS were investigated using fluorescence, infrared spectra and scanning electron microscopy. The specific surface area of all materials was calculated by Branauer, Emmett and Teller （BET） method using nitrogen isotherm adsorption data. As the results, the surface area of commercial silica gel decreased from 609.2 to 405.4 m2/g, it indicated that the pyoverdin I could be immobilized onto the surface of silica solid support. This adsorbent was used for extraction of Fe（Ⅲ）, Cu（Ⅱ）, Zn（Ⅱ）, and Pb（Ⅱ） in artificial metals contaminated water. Experimental conditions for effective adsorption of trace levels of metal ions were optimized with respect to different experimental parameters using batch procedure. The optimum pH value for the removal of metal ions simultaneously on this adsorbent was 4.0. Complete desorption of the adsorbed metal ions from the adsorbent was carried out using 0.25 mol/L of EDTA. The effect of different cations and anions on the adsorption of these metals on adsorbent was studied and the results showed that the proposed adsorbent could be applied to the highly saline samples and the sample which contains some transition metals.

Kinetic Study for Adsorption of Heavy Metals on Zeolite

Heavy metals⁃polluted water has negative impact on the ecosystem.In Malaysia,minimum discharge limit for Cu^(2+)and Zn^(2+)are 1 mg/L and 2 mg/L,respectively.Zeolite is a highly porous adsorbent and its performance is affected by various factors,including contact time and pH.Thus,the objective of this study is to identify an ideal operating condition to treat Cu^(2+)and Zn^(2+)solutions up to the allowable discharge limit,by considering the pH and contact time factors.Six kinetic models were studied to identify the adsorption mechanism of the heavy metal removal process.Single solute batch adsorption experiment was conducted within pH 3-11 from 30 to 150 min.Results showed that hydration enthalpy(ΔHhyd)governed the selectivity of heavy metals,where a maximum of 90.87%Zn^(2+)(ΔH_(hyd)=-1955 kJ/mol)and 82.15%Cu^(2+)(ΔH_(hyd)=-2010 kJ/mol)removals were found at pH≥7.Without pH adjustment,selectivity towards Cu^(2+)was higher compared with Zn^(2+)due to the size of hydration radii,where Cu^(2+)is 0.11Åsmaller than Zn^(2+).By considering both pH and contact time factors,this study shows that by adjusting the pH of Zn^(2+)solutions to a minimum pH value of 7,the contact time required to achieve maximum Zn^(2+)removal rate was 90%,which can be achieved within 60 min.Meanwhile,zeolite performed better in Cu^(2+)removal without any pH adjustment where a maximum of 94%was achieved at 120 min.Final concentration of 0.523 mg/L Cu^(2+)and 0.981 mg/L Zn^(2+)were obtained in this study.Kinetic study showed that Ritchie’s equation predicted Cu^(2+)adsorption the best,while Zn^(2+)adsorption could be represented by Elovich model.This suggested that the adsorption on the activate site governed Cu^(2+)and Zn^(2+)removal process.Hence,future work should focus on modifying zeolite surface to improve the adsorptive performance.

Removal of Heavy Metals by Two Free Floating Aquatic Macrophytes

A concentration-dependent decrease in biomass, protein, RNA, DNA, and nutrient (NO3- and PO43-) uptake of Lemna minor and Azolla pinnata by Cr, Ni, and Zn was detected. Cr was found to exert maximum toxicity followed by Ni and Zn. Metal uptake was dependent on time and concentration of metal in the external rnedium. Both the macrophytes, however, showed preference for Zn followed by Ni and Cr. The uptake kinetics also revealed a low Vmax and high Km for Cr. L. minor was more effcient in accumulating Zn and Cr than A. pinnata in Ni. Compared to immobilized algae and bacterial capsules the test macrophytes showed a greater efficiency for metal removal

Fabrication of Poly（y-glutamic acid）-coated Fe3O4 Magnetic Nanoparticles and Their Application in Heavy Metal Removal

In this study, poly（y-glutamic acid）-coated Fe3O4 magnetic nanoparticles （y-PGA/Fe304 MNPs） were successfully fabricated using the co-precipitation method. Fe3O4 MNPs were also prepared for comparison. The av erage size and specific surface area results reveal that 7-PGA/Fe304 MNPs （52.4 nm, 88.41 m2.g-1） have smaller particle size and larger specific surface area_ than Fe3O4 MNPs （62.0 nm, 76.83 mLg-1）. The y-PGA/Fe3O4 MNPs

Enhancement of removal efficiency of heavy metal ions by polyaniline deposition on electrospun polyacrylonitrile membranes

This paper describes the preparation of a membrane of polyacrylonitrile(PAN)and its corresponding membrane coated with polyaniline(PANI)for the adsorption of heavy metal ions.Scanning electron microscopy micrographs revealed that all the membranes exhibited nanofibrous morphology.The prepared membranes were characterized by Fourier transform infrared spectroscopy(FTIR).The prepared membranes were used as an adsorbent for hazardous heavy metal ions Pb^(2+) and Cr_(2)O^(2-)_(7).The adsorption capacity and the removal efficiency of the membranes were examined as function of the initial adsorbate concentration and pH of the medium.Coated membranes with PANI showed better adsorption performance and their direct current(DC)conductivities were correlated to heavy metal ion concentrations.Adsorption isotherms were also performed,and the adsorption process was tested according to the Langmuir and Freundlich models.The regeneration and reuse of the prepared membranes to re-adsorb heavy metal ions were also investigated.The enhancement in adsorption performance and reusability of PANI-coated membranes in comparison with non-coated ones is fully discussed.The results show that the maximum adsorption capacities of lead and chromate ions on the PANI-coated membranes are 290.12 and 1202.53 mg/g,respectively.

Additive manufacturing of sodalite monolith for continuous heavy metal removal from water sources

Herein,we present a simple strategy for preparing monolithic sodalite adsorbents via sequential additive manufacturing and post-treatments.In detail,the method includes(i)3D printing of cylindrical monoliths using clay as the base material;(ii)thermal activation of the 3D-printed clay monoliths by calcination(to produce reactive alumina and silica species and enable mechanical stabilization);(iii)conversion of the activated clay monoliths to hierarchical porous sodalite monoliths via hydrothermal alkaline treatment.Parametric studies on the effect of calcination temperature,alkaline concentration and hydrothermal treatment time on the property of the resulting materials(such as phase composition and morphology)at different stages of preparation was conducted.Under the optimal conditions(i.e.,calcination temperature of 850℃,NaOH concentration of 3.3 mol·L^(-1),reaction temperature of 150℃,and reaction time of 6 h),a high-quality pure sodalite monolith was obtained,which possesses a relatively high BET surface area(58 m^(2)·g^(-1))and hierarchically micro-meso-macroporous structure.In the proposed application of continuous removal of heavy metals(chromium ion as the model)from wastewater,the developed 3D-printed sodalite monolith showed excellent Cr^(3+)removal performance and fast kinetics(~98%removal efficiency within 25 cycles),which outperformed the packed bed using sodalite pellets(made by extrusion).

Comparative evaluation of processes for heavy metal removal from municipal solid waste incineration fly ash

Hydrochloric acid leaching, chloride evaporation, acetic acid leaching, and biological leaching were evaluated and compared as processes of heavy metal removal for municipal solid waste incineration fly ash(MSWFA). Six factors, namely, energy consumption, process efficiency, process handling, process cost estimation, cost reduction potential, and study progress, were used in order to find out their advantages and disadvantages and to help develop a better recovery process of heavy metals from MSWFA in terms of treatment of the waste material. Hydrochloric acid leaching process was found to be most balanced among the evaluated processes. It showed superiority on energy consumption, process cost estimation, and study progress. On the other hand, despite of its excellency in process efficiency, chloride evaporation process was most unfavorable mainly due to heavy energy dependence. Biological process, with huge potential of cost reduction, was concluded to be the second best process.

Plants grown on sewage sludge in South China and its relevance to sludge stabilization and metal removal

The production of sewage sludge in China has been increasing sharply in order to treat 40% of the municipal sewage in 2005 as planned by central government. The main sludge disposal method is landfill owing to heavy metal contamination, but it presents an attractive potential for agricultural land application. Experiments were carried out to study the simultaneous metal removal and sludge stabilization by plants. The sludge samples were collected from Datansha Wastewater Treatment Plant of Guangzhou, it contained excessive Cu and Zn compared with the Chinese National Standard for Agricultural Use of Sewage Sludge. Plants growing on sludge beds were investigated to follow their growth and metal uptake. 30 sludge plants were identified during 1 year's observation. A Zn high accumulating and high growth rate plant (Alocasia macrorrhiza) was selected and grown on sludge beds in plots. The water, organic matter, heavy metals and nutrients contents, the E. coli number and the cress seed germination index were monitored for the sludge samples collected monthly. The plant growth parameters and its heavy metals contents were also determined. The sewage sludge treated by plants could be stabilized at about 5 months, the E. coli number was significantly decreased and the cress seed germination index attained 100%. Crop on sludge could ameliorate the sludge drying. The experiments are continuing to find out the appropriate plant combination for simultaneous sludge stabilization and metal removal for an acceptable period. Comparisons between the proposed processes and other methods for treating produced sludge such as composting, chemical and bacterial leaching were discussed.

Batch studies of adsorption of copper and lead on activated carbon from Eucalyptus camaldulensis Dehn. bark

Powdered activated carbon (PAC) prepared from Eucalyptus camaldulensis Dehn. bark was tested for its adsorption capacity for Cu(Ⅱ) and Pb(Ⅱ). The experiment was conducted to investigate the effects of pH, contact time, initial metal concentration, and temperature. The best adsorption of both Cu(Ⅱ) and Pb(Ⅱ) occurred at pH 5, where the adsorption reached equilibrium within 45 min for the whole range of initial heavy metal concentrations (0.1-10 mmol/L). The adsorption kinetics was found to follow the pseudo-...

The synthesis and application of zeolitic material from fly ash by one-pot method at low temperature

A new route to prepare zeolitic material was introduced in this work. Compared with traditional methods, the new route showed lower energy consume. The effect of pre-treatment conditions on structure and crystalline phase was investigated, revealing that the mullite crystalline phase in fly ash could be converted to amorphous phase by alkali at low temperature. The removal performance of heavy metal ions on designed material was also investigated, and we found that the intermediate product showed higher adsorption capacity on Ni^(2+) than zeolite A.

Kinetics and mechanism of adsorptive removal of copper from aqueous solution with poly(vinyl alcohol) hydrogel

Recently, a renewed interest in techniques for heavy metal removal of wastewater has been growing because of embarking opportunities for industrial applications. We investigated the adsorption capacity of the copper on the poly（vinyl alcohol） hydrogel from the aqueous solution. Chemical structure and water absorption of the hydrogel were studied using FTIR and water uptake measurement, respectively. The results showed that the poly（vinyl alcohol） was crosslinked with glutaraldehyde, and the hydrogel highly exhibited the equilibrium swelling ratio because of its hydrophilicity property. Additionally, it was found that the adsorption process followed the pseudo-second-order kinetics and the mechanism diffusion was controlled by particle and film diffusions.

A fully bio-sourced adsorbent of heavy metals in water fabricated by immobilization of quinine on cellulose paper

The fabrication of a fully bio-sourced adsorbent of Cd(Ⅱ)by covalent immobilization of quinine on cellulose paper is described.The double bond of commercially available quinine was converted to a terminal alkyne function which was reacted with cellulose paper,chemically modified with azide functions,through a 1,3-dipolar cycloaddition,leading to Cell-Quin.The adsorption efficiency of Cell-Quin was investigated to determine the optimal pH,contact time and dose of adsorbent,ultimately leading to high levels of removal.The mechanism of adsorption of Cell-Quin was deeply rationalized through kinetic experiments and isotherm modeling.We also showed that Cell-Quin could adsorb other heavy metals such as Cu(Ⅱ),Pb(Ⅱ),Ni(Ⅱ)and Zn(Ⅱ).

Removal of Cu(II),Pb(II),Mg(II),and Fe(II) by Adsorption onto Alginate/Nanocellulose Beads as Bio-Sorbent

Alginate blended with cellulose nanocrystals(CNC),cellulose nanofibers(CNF),and tri-carboxylate cellulose nanofibers(TPC-CNF)prepared and encapsulated in the form of microcapsules(bio-polymeric beads).The cellulosic nanomaterials that used in this study were investigated as nanomaterials for wastewater treatment applications.Batch experiments were performed to study the removal of copper,lead,magnesium,and iron from aqueous solutions by the prepared beads.The effects of the sorbent dosage and the modified polymers on the removing efficiency of the metal cations were examined.Atomic absorption was used to measure the metal ions concentrations.The modified bio-polymeric beads(Alg-CNF,Alg-CNC,and Alg-TPC-CNF)exhibited high-efficiency towards removing of the metal cations;Cu^(2+),Pb^(2+),Mg^(2+),and Fe^(2+).The Alg-TPC-CNF composite was exhibited excellent removing efficiency which around 95%for Pb,92%for Cu,43%for Fe and 54%for Mg.These outcomes affirm that the utilization of nanomaterials giving higher adsorption capacities contrasted with similar material in its micro or macrostructure form.

Batch and fixed-bed column studies of selenite removal from contaminated water by orange peel-based sorbent

Orange peel is a biomass derived from citrus processing with desirable properties for metal sorption.In recent years,orange peel has been used to remove various heavy metals and toxic oxyanions.Selenium(Se)is an essential trace element for mammals.However,when the concentration of selenium exceeds an umbral limit,it becomes toxic.In this study,orange peel was used to treat Se(IV)-contaminated water.A high sorption capacity of 32.5 mg/g was obtained at a temperature of 20℃and a pH of 2.0.Hydroxyl groups bound Se(IV)to the surface of the orange peel.The sorption process was spontaneous and endothermic.A chemical sorption mechanism was involved in the removal of Se(IV).The Thomas and modified dose-response models were used to simulate the experimental breakthrough curves.The bed depth service time model was used to calculate the critical bed depth(Z0),and the calculated Z0 value was 1.6 cm.This study reveals that orange peel is a useful sorbent for Se(IV),and can be used for the purification of Se(IV)-contaminated water.©2020 Hohai University.Production and hosting by Elsevier B.V.This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).

Treatment of mine drainage generated by lead-zinc concentration plant

The purification efficiency in the treatment of the mine drainage generated by the mineral processing industry in Mengzi,Yunnan Project, China, was investigated, and the influences of the treated drainage on the mineral electrodes' electrochemical behaviors were tested. Experiments with different doses of polyacrylamide(PAM) and polymeric ferric sulfate(PFS) at different pH values were carried out, and the advanced purification by activated carbon(AC) was conducted. Compared with PFS, the better coagulant for removal efficiency is PAM, under the optimal conditions, the removals of Pb2+, Zn2+, Cu2+ and COD reduction from solution were 94.8%, 79.9%, 87.6% and 85%, respectively. In the advanced purification, the particle size of activated carbon and agitation time played important roles in the removal efficiency. Each pollute concentration could meet the emission standard of pollutants for lead and zinc industry(GB25466—2010). The wastewater without treatment affected galena and sphalerite electrochemical behaviors greatly, after treatment by the technology, the effects disappeared, which proved the reliability of the technology for wastewater treatment.

Recovery and Upgrading of Phosphorus from Digested Sewage Sludge as MAP by Physical Separation Techniques

Physical separation apparatuses;a vibrating screen, a 4-inch hydrocyclone and a Multi-Gravity Separator (MGS) were used to recover phosphorus as MAP (magnesium ammonium phosphate, MgNH4PO4.6H2O) from anaerobic digested sludge of two sewage-treatment plants A and B. For plant A, the MAP grade increased from 0.08% to 88.9% with 90.4% recovery and for plant B, the grade increased from 0.11% to 73.8 with 93.2% recovery. The collected MAP products containing impurities such as organic materials and heavy metals were further upgraded through dry and wet magnetic separation tests at different magnetic flux densities. A dry magnetic separator was tested on both MAP products (MAP-A and MAP-B), while the wet magnetic separation process was exclusively experimented for the removal of impurities from MAP-B. Feed samples, as well as magnetic and nonmagnetic products were analyzed by absorption spectroscopy, XRD, ICP-AES, polarizing microscope observation, and SEM-EDX. The grade of MAP products could be improved by about 4% - 9% after magnetic separation (the most appropriate magnetic force being 15,000 Gauss). During both dry and wet magnetic separation processes, not only heavy metals have been removed, but also nonmagnetic constituents like Al, Ba, and Ca. This may be attributed to the attachment of fine magnetic particles on the nonmagnetic surfaces, rendering them magnetic properties.

聚多巴胺增强的高稳定性二维AgCrSe_(2)膜用于污水净化

传统二维纳米片膜在分子和离子分离领域具有巨大潜力,然而在实际污水处理中不可避免地会出现溶胀和易氧化的问题.本研究利用一种新型二维纳米片AgCrSe_(2),采用聚多巴胺(PDA)原位交联策略,成功构筑了高稳定性二维AgCrSe_(2)-PDA膜.该膜能够耐受酸性、碱性介质以及氧化性溶液(0.3 wt%过氧化氢),展现出优异的抗溶胀和抗氧化稳定性.此外,该膜对带负电的染料和乙二胺四乙酸(EDTA)络合的重金属离子的截留率接近100%,通量约为5.0 L m^(−2) h^(−1) bar^(−1).值得注意的是,经过140小时的错流过滤,尽管膜通量略有下降,但该膜对CuEDTA的截留率仍保持在90%左右.这种高稳定性的膜结构源自于PDA与AgCrSe_(2)纳米片之间的配位相互作用.本研究为开发高稳定性的二维膜提供了有效的策略,为工业污水净化提供了新型膜材料.

Fast removal of heavy metal ions and phytic acids from water using new modified chelating fiber

The graft copolymerization of acrylic acid（AA） onto polyethylene glycol terephthalate（PET） fiber initialed by benzoy peroxide （BPO） was carried out in heterogeneous media.Moreover,modification of the grafted PET fiber（PET-AA） was done by changing the carboxyl group into acylamino group through the reaction with dimethylamine.The modified chelating fiber（NDWJN1） was characterized using elementary analysis,SEM and FT-IR spectroscopy.Adsorption kinetic curves indicated that NDWJNl could fast remove heavy metal ions and phytic acids from water effectively.Furthermore,batch kinetic studies indicated that heavy metal ions adsorbed to NDWJNl could be filted well by both pseudo-first-order and pseudo-second-order adsorption equations,but the intra-particle diffusion played a dominant role in the adsorption of phytic acids.

Preparation of core-shell magnetic Fe_3O_4@SiO_2-dithiocarbamate nanoparticle and its application for the Ni^(2+), Cu^(2+) removal

A novel magnetic nanoparticles-based dithiocarbamate absorbent（Fe3O4@SiO2-DTC） with core-shell structure was synthesized under mild conditions and used in aqueous solution Ni2＋ and Cu2＋ ions treatment. The structure, morphology and magnetic properties of the adsorbent were characterized by Xray diffraction（XRD）, fourier transformed infrared spectroscopy（FTIR）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, and vibrating sample magnetometer（VSM）.Fe3O4@SiO2-DTC exhibited a typical superparamagnetic with a saturation magnetization value of52.7 emu/g, which could be rapidly separated from aqueous solution under external magnetic field. We investigated the effects of solution p H, adsorption time, and the initial concentration of heavy metal ions on the adsorption of Ni2＋ and Cu2＋. The adsorption equilibrium times of Ni2＋and Cu2＋ on Fe3 O4@SiO2-DTC were reached at 15 min and 90 min, respectively. The adsorption kinetic data were fitted to the pseudosecond-order model, and the adsorption data were consistent with the Frenudlich isotherm model. When the initial concentration of heavy metal ions was 250 mg/L, the maximum adsorption capacity of Ni2＋ and Cu2＋ at room temperature was 235.23 mg/g and 230.49 mg/g, respectively. In addition, we discussed the plausible adsorption mechanism. The results indicated that the adsorption was mainly dominated by chelation.