Removal Efficiency Of Ions Research Articles

Mechanistic insight and optimisation of hydrothermally pre-treated biowaste-derived biochar for saline water treatment

The valorisation of oil palm empty fruit bunch is challenging due to its poor surface functionalities, which require a comprehensive pre-treatment process. To ensure efficient valorisation of the agricultural waste, the biochar derived from empty fruit bunch is subjected to hydrothermal nitric acid pre-treatment to act as an adsorbent for sodium ions removal from the saline solution. For this newly developed adsorbent, the adsorption study provides important information on the adsorption behaviour of sodium ions and the optimum conditions for sodium ions removal, which is crucial for effective process design and operation control during practical applications. Physicochemical characterisation revealed the successful adsorption of sodium ions by Hydrothermal Nitric acid Pre-treated EFB Biochar (HNO3 EFB-BC. The highest sodium ions removal efficiency of HNO3 EFB-BC (92.04%) was achieved under the optimum reaction conditions: 0.39 M initial concentration of the saline solution, 4.96 g of HNO3 EFB-BC, contact time of 17.4 h and solution pH of 7.46. Upon process optimisation, the adsorption capacity of HNO3 EFB-BC towards sodium ions improved remarkably (p < 0.05) from 78.34 mg g-1 to 166.45 mg g-1. The adsorption isotherm and kinetic study are consistent with the Langmuir and pseudo-second-order models, implying a monolayer chemisorption-dominated adsorption process. The promising sodium ions adsorption capacity of HNO3 EFB-BC can be attributed to the enhanced surface functionalities of the adsorbent. The molecular modelling using the density functional theory approach has successfully identified the nitro group as the most favourable functional group in producing the charges sites for sodium ions adsorption, with the most stable reaction route between HNO3 EFB-BC and sodium ions being identified. This study highlighted the density functional theory approach as a tool for identifying the specific functional groups with enhanced adsorption capability for saline water treatment and provides a reference value for removing sodium ions in the presence of other cationic pollutants.

An advanced treatment process for 3-high wastewater discharged from crude oil storage tanks.

The wastewater discharged from crude oil storage tanks (WCOST) contains high concentrations of salt and metal iron ions, and high chemical oxygen demand (COD). It belongs to "3-high" wastewater, which is difficult for purification. In this study, WCOST treatments were comparatively investigated via an advanced pretreatment and the traditional coagulation-microfiltration (CMF) processes. After WCOST was purified through the conventional CMF process, fouling occurred in the microfiltration (MF) membrane, which is rather harmful to the following reverse osmosis (RO) membrane unit, and the effluent featured high COD and UV254 values. The analysis confirmed that the MF fouling was due to the oxidation of ferrous ions, and the high COD and UV254 values were mainly attributable to the organic compounds with small molecular sizes, including aromatic-like and fulvic-like compounds. After the pretreatment of the advanced process consisting of aeration, manganese sand filtration, and activated carbon adsorption in combination with CMF process, the removal efficiencies of organic matter and total iron ions reached 97.3% and 99.8%, respectively. All the water indexes of the effluent, after treatment by the advanced multi-unit process, meet well the corresponding standard. The advanced pretreatment process reported herein displayed a great potential for alleviating the MF membrane fouling and enhanced the lifetime of the RO membrane system in the 3-high WCOST treatment.

Boron and lithium recovery from aqueous solutions by ion-exchange resin stuffed electro-electrodialysis process with hydrogen production

A considerable amount of lithium is released in the wastes generated during the boron mineral enrichment process. Hence, there is a need to develop systems or processes to recover lithium and boron minerals from the waste of mining industries. In this context, electro-membrane processes have gained importance in literature recently. This study proposes a novel electro-membrane process to recover lithium and boron from an aqueous solution and simultaneous hydrogen production using an electro-electrodialysis stack composed of monovalent-anion and monovalent-cation-exchange membranes filled with ion-exchange resins. The effect of the operating parameters, such as current density, flow rate, pH type of ion-exchange resins, and initial conductivity value of the aqueous solution, on the system efficiencies are investigated. Finally, the proposed electrochemical stack's energy consumption and hydrogen production rates are calculated based on the measurements. The results reflect that maximum conductivity removal efficiency is achieved at 90% by the electro-electrodialysis process with ion-exchange resins. The highest removal efficiency of boron and lithium ions are achieved via electro-electrodialysis with ion-exchange resin as 95.1% and 99.5%, respectively. The hydrogen gas production rate is calculated as 13.55 mmol/h with the same configuration and adding ion-exchange resins to the electro-electrodialysis process improves hydrogen production by 8.6%. Finally, the net energy consumption is calculated as 6.1 kWh/m3 of synthetic wastewater. This study presents a promising method to produce hydrogen and recover valuable minerals of boron and lithium from the aqueous waste solutions.

Study of morphological aspects in the efficient adsorptive removal of heavy metal ions using graphene oxide-chitosan based magnetic nanocomposite (0.4Fe0x:6x@GCS)

A one pot approach is followed to achieve an optimized synthesis of a benign magnetic nano composite and its applicability is explored in alleviation of toxic heavy metal ions from contaminated water. Untreated industrial effluents are among one of the major contributors in escalating the levels of heavy metals in residual water and soil, hence posing a serious threat to the humankind and the environment. With the motive in mind to treat such effluents, we fabricated a magnetic ternary nano-composite (NC) Fe0x:x@GCS (x:x is the concentration of Fe(II): concentration of NaBH4) aiming to reduce the levels of heavy metal ions (Pd, Cd, Cu & Ni) in polluted water. The initial concentration of Fe (II) precursor salt and the dosage of the reducing agent (NaBH4) were tactically adjusted to get desirable morphological and structural features in ultimate magnetic Fe0x:x@GCS NC with profound effect in eliminating the heavy metals ions from waste water. The effects of varying these two factors on the overall removal efficiency of heavy metal ions of the Fe0x:x@GCS are studied and analyzed. XRD, SEM & EDS techniques are used for the study of morphological and structural aspects of the synthesized materials and their comparative analysis. The reaction kinetics of the removal process of Pb(II) ions by the Fe0x:x@GCS NC was found best fitted to pseudo second order kinetics and the reaction isotherm was found better explained by Langmuir isotherm. Mechanistic aspects of the removal process of Pb (II) ions could be explained by XRD analysis of NC before and after the treatment with polluted water. Furthermore, to simulate the real waste water conditions, a mixture containing Pb (II), Cd (II), Ni (II) and Cu (II) heavy metal ions was also treated with NC which exhibited the removal efficiency of >99% .

Recovery of Phosphate(V) Ions from Water and Wastewater Using Chitosan-Based Sorbents Modified-A Literature Review.

Over the past two decades, there has been increasing interest in the use of low-cost and effective sorbents in water treatment. Hybrid chitosan sorbents are potential materials for the adsorptive removal of phosphorus, which occurs in natural waters mainly in the form of orthophosphate(V). Even though there are numerous publications on this topic, the use of such sorbents in industrial water treatment and purification is limited and controversial. However, due to the explosive human population growth, the ever-increasing global demand for food has contributed to the consumption of phosphorus compounds and other biogenic elements (such as nitrogen, potassium, or sodium) in plant cultivation and animal husbandry. Therefore, the recovery and reuse of phosphorus compounds is an important issue to investigate for the development and maintenance of a circular economy. This paper characterizes the problem of the presence of excess phosphorus in water reservoirs and presents methods for the adsorptive removal of phosphate(V) from water matrices using chitosan composites. Additionally, we compare the impact of modifications, structure, and form of chitosan composites on the efficiency of phosphate ion removal and adsorption capacity. The state of knowledge regarding the mechanism of adsorption is detailed, and the results of research on the desorption of phosphates are described.

Dyes and Heavy Metals Removal from Aqueous Solutions Using Raw and Modified Diatomite

The progress of the textile industry has led to a severe increase in the discharge of colored effluents, polluted with dyes and metal ions (non-biodegradable, carcinogenic to humans and environmental hazards). The implementation of effective methodologies and materials for the treatment of wastewater has become an urgent requirement. The present work describes the application of two samples of mineral materials—Ghidirim diatomite and modified diatomite—as adsorbents for the removal of dyes—Acid Blue 350, Methylene Blue, Basic Red 2—and of metal ions—copper, zinc, and lead—from aqueous solutions. In order to determine the optimal working conditions by which to ensure maximum removal efficiency, the influence of the nature and amount of the sorbent, the initial concentration of pollutant, and the temperature were studied. Working under normal conditions (room temperature, solution pH) efficiencies greater than 80% were obtained for the removal of dyes and metal ions. The adsorption fitted well with the pseudo-second order kinetic model, and the maximum adsorption capacities were determined from the Langmuir isotherm model. The adsorption of investigated pollutants is an endothermic and spontaneous process. The results indicate that Ghidirim diatomite and modified diatomite have potential applications in water purification management, providing high removal efficiency of both dyes and metal ions.

A precise pyromellitic acid grafting prepared multifunctional MXene membranes for efficient oil-in-water emulsion separation and heavy metal ions removal

Industrial development generates large quantities of oily wastewater, which poses a serious threat to the environment and human health. Heavy metal ions, dyes, and some water-soluble pollutants are also discharged with oily wastewater. Therefore, there is an urgent need for multifunctional separation technologies to deal with various pollutants. As an emerging two-dimensional material, titanium carbide (Ti3C2Tx) is of great importance in the field of oil–water separation because of the abundant hydrophilic groups on its surface. Herein, we developed a precise grafting strategy to modify MXene sheets with pyromellitic acid groups and prepared a multifunctional MXene-based membrane. Benefit from the abundant hydrophilic groups on the MXene sheets’ surface, the as-prepared membrane demonstrated outstanding superhydrophilic and anti-oil adhesion properties, and also showed remarkable separation performance (6731.8 L m−2 h−1 bar−1 and >99.97%) for high viscosity emulsions. Importantly, the presence of grafting groups improved the removal efficiency of several heavy metal ions (>99%) by the membrane. Additionally, it also demonstrated superior chemical stability, flexibility, and efficient separating harsh emulsions. This work provides a new insight into the development of the multifunctional MXene-based membrane materials.

Effectiveness of polyethylene glycol-coated silica on ions adsorption in industrial wastewater

The effect of coating silica with polyethylene glycol on the adsorption of iron and phosphate ions in industrial wastewater was investigated. Variable factors were temperature and time of coating, PEG concentration, and PEG to silica ratio. Infrared spectroscopy and scanning electron microscopy were used to evaluate the chemical structure and morphology of PEG-coated silica. Optimum iron and phosphate ions removal efficiency was obtained using a coating temperature of 50°C, a coating time of 15 min, a PEG concentration of 20%, and a PEG to silica ratio of 1:3.

Tris(2-benzimidazolyl)amine (NTB)-Modified Metal-Organic Framework: Preparation, Characterization, and Mercury Ion Removal Studies

Heavy metal ions (HMIs) are exceedingly hazardous to both humans and the environment, and the necessity to eliminate them from aqueous systems prompted the development of novel materials. In this study, tris(2-benzimidazolylmethyl)amine (NTB) was impregnated into MIL-101-(Cr) metal-organic framework using an incipient wetness impregnation approach, and the ability of the composite material to adsorb Hg2+ ions from the water was examined. The synthesized materials were analyzed with several physico-chemical techniques such as powder X-ray diffraction, elemental analysis, scanning electron microscopy, thermogravimetric analysis, nitrogen sorption isotherms at 77 K, and X-ray photoelectron spectrometry. MIL-101-NTB quickly adsorbs 93.9% of Hg2+ ions within 10 min from a 10.0 ppm single ion solution. A better fit of the kinetic data to a pseudo-second-order model validated the chemisorption of Hg2+ ions on MIL-101-NTB. The experimental data fitted well with the Langmuir isotherm model, and the maximum adsorption capacity obtained at 125 ppm initial concentration was 111.03 mg/g. Despite the presence of other competing ions (Cu2+, Pb2+, and Cd2+), high Hg2+ ions removal efficiency (99.6%, 1.0 ppm initial concentration) was maintained in the diverse ion batch adsorption studies. A 0.2 M EDTA solution could desorb the Hg2+ ions, and cyclic Hg2+ ions sorption studies indicated that MIL-101-NTB might have a high Hg2+ ions removal efficiency for at least five consecutive cycles. Based on the FTIR and XPS analyses, Hg2+ ions chelation by NTB molecules and electrostatic interactions between Hg2+ ions and carboxylate groups in MIL-101-NTB are plausible mechanisms for Hg2+ ions adsorption.

Adsorption and desorption ability of divalent mercury from an interactive bicomponent sorption system using hybrid granular activated carbon.

The sequestration of heavy metals from multicomponent sorption media has become critical due to the noxious effects of heavy metals on the natural environment and subsequently on human health as well as all life forms. The abatement of heavy metals using bio-adsorbents is one of the efficient and affordable approaches for treating water and wastewater. Therefore, the interactive effect of arsenic [As(III)] ions on the sorption and desorption ability of mercury [Hg(II)] from a binary sorption system was conducted. More so, the impact of reaction time, solution pH, bio-adsorbent particle size, bio-adsorbent dose, initial mono-metal, and binary-metal concentration as well as reaction temperature on the individual and competitive sorption of Hg(II) was explored. The study showed that Hg(II) could be removed effectively from the single-component system and competitively from the aqueous phases by the bio-adsorbent in the coexistence of As(III) species in the bicomponent medium. The adsorptive detoxification of Hg(II) from the monocomponent and bicomponent sorption media showed dependence on all the studied adsorption parameters. The occurrence of As(III) species in the bicomponent sorption medium affected the decontamination of Hg(II) by the bio-adsorbent and the major interactive mechanism was found to be antagonism. The spent bio-adsorbent was effectively recycled using 0.10 M nitric (HNO3) and hydrochloric (HCl) acids solutions and the multi-regeneration cycles showed ahigh removal efficiency in each cycle. The first regeneration cycle was found to have the highest Hg(II) ions removal efficiencies of 92.31 and 86.88% for the monocomponent and bicomponent systems, respectively. Thus, the bio-adsorbent was found to be mechanically stable and reusable up to the 6.00 regeneration cycle. Therefore, this study concludes that the bio-adsorbent not only has a higher adsorption capacity but also a good recycling performance pointing to good industrial applications and economic prospects.

Carbonaceous MnFe2O4 nano-adsorbent: Synthesis, characterisation and investigations on chromium (VI) ions removal efficiency from aqueous solution

Carbonaceous manganese ferrite nanoparticles were prepared at relatively lower temperature using co-precipitation method followed by a single-step pyrolysis process. Synthesized nanoparticles were further characterized by different spectroscopic and microscopic techniques. The X-ray Diffraction (XRD) study confirmed the formation of single phase cubic spinel structure and the presence of graphitic carbon of plane (002) and the size of the prepared nanostructure was of 36 nm. With the confirmation of formation of carbonaceous MnFe2O4 and the number of oxygen functionalities such as hydroxyl and C-O-C groups emanating from the carbon matrix, as confirmed by the Fourier Transform Infrared (FT-IR) studies motivated their usage to remove Cr (VI) ions from aqueous solution. The study parameters such as influence of time, adsorbent dosage, concentration and pH are explored along with isotherm and kinetic studies. The carbonaceous nanoparticle was able to remove Cr (VI) by ∼80% at native pH, with a carbonaceous MnFe2O4 dose of 10 mg, and the initial concentration 10 ppm of contaminant with the contact time, 80 min and is found promising for the practical applications.

Methods for removing chloride ions to manufacture zinc from arc melting dust

In this work, we review literature sources to identify an industrial-scale technology for manufacturing cathode zinc from technogenic chlorine-containing raw materials of a complex chemical composition, in particular, from arc melting dust. The conducted review of Russian and foreign publications was used to search for a method of purifying process solutions with a high concentration of chloride ions produced by hydrometallurgical processing of technogenic arc melting dusts. It was found that the existing purification methods are associated with substantial limitations, including strict requirements for the acidity of the treated solution, low efficiency of treatment, secondary contamination of the medium by released chloride ions, and the high cost of reagents or equipment. Approaches to reducing the chlorine content in the initial dust and dechlorination of process solutions based on principles of sedimentation, ion exchange, sorption, and oxidation are described. In addition, we analyzed information published on chlorine removal from process effluents and solutions of various nature. Industrially-implemented and recently-reported laboratory methods of solution dechlorination were compared in terms of their feasibility, economic efficiency, and extent of chloride ion removal. It was concluded that the disadvantages of existing methods for processing technogenic chlorine-containing raw materials of arc melting can be eliminated by developing large, stable, and cheap hydride technologies based on principles of extraction, ion exchange, and sedimentation.

Composite Membrane Based on Melamine Sponge and Boehmite Manufactured by Simple and Economical Dip-Coating Method for Fluoride Ion Removal.

The wastewater generated from the semiconductor production process contains a wide range and a large number of harmful substances at high concentrations. Excessive exposure to fluoride can lead to life-threatening effects such as skin necrosis and respiratory damage. Accordingly, a guideline value of fluoride ions in drinking water was 1.5 mg L-1 recommended by the World Health Organization (WHO). Polyvinylidene fluoride (PVDF) has the characteristics of excellent chemical and thermal stability. Boehmite (AlOOH) is a mineral and has been widely used as an adsorbent due to its high surface area and strong adsorption capacity for fluoride ions. It can be densely coated on negatively charged surfaces through electrostatic interaction due to its positively charged surface. In this study, a composite membrane was fabricated by a simple and economical dip coating of a commercial melamine sponge (MS) with PVDF and boehmite to remove fluoride ions from semiconductor wastewater. The prepared MS-PVDF-Boehmite composite membrane showed a high removal efficiency for fluoride ions in both incubation and filtration. By the incubation process, the removal efficiency of fluoride ions was 55% within 10 min and reached 80% after 24 h. In the case of filtration, the removal efficiency was 95.5% by 4 cycles of filtering with a flow rate of 70 mL h-1. In addition, the removal mechanism of fluoride ions on MS-PVDF-Boehmite was also explored by using Langmuir and Freundlich isotherms and kinetic analysis. (R2-1) From the physical, chemical, thermal, morphological, and mechanical analyses of present materials, this study provides an MS-PVDF-Boehmite composite filter material that is suitable for fluoride removal applications due to its simple fabrication process, cost-effectiveness, and high performance.

Experimental Study on Desulfurization and Ceramic Tile Preparation of Gold Cyanide Tailing

Desulfurization and ceramic tile preparation of gold cyanide tailing have been carried out. A novel oxidant DDTQ has been successfully applied to collaborative decyanation and desulfurization. The removal efficiency of cyanide ions can exceed 99%, and the reduction rate of pyrite and chalcopyrite can be achieved above 90% at the same time with wet oxidation process. Ceramic tiles have been successfully prepared by adding sulfur fixing agent composites during the firing process. The fixing mechanism of residual sulfur after oxidative desulfurization has also been proposed.

Multivariate modeling and process optimization of Hg(II) remediation using solvothermal synthesized 2D MX/Fe3O4 by response surface methodology: characteristics and mechanism study.

Two-dimensional MXene with layered structure has recently emerged as a nanomaterial with fascinating characteristics and applicability. Herein, we prepared the newly modified magnetic MXene (MX/Fe3O4) nanocomposite using solvothermal approach and investigated its adsorption behavior to study the removal efficiency of Hg(II) ions from aqueous solution. The effect of adsorption parameters such as adsorbent dose, time, concentration, and pH were optimized using response surface methodology (RSM). The experimental data fitted well with quadratic model to predict the optimum conditions for maximum Hg(II) ion removal efficiency which were found to be at adsorbent dose0.871g/L, time103.6min, concentration40.17mg/L, and 6.5 pH respectively. To determine the adequacy of the developed model, a statistical analysis of variance (ANOVA) was used, which demonstrated high agreement between the experimental data and the suggested model. According to isotherm result, the experimental data were following the best agreement with the Redlich-Peterson isotherm model. The results of the experiments revealed that the maximum Langmuir adsorption capacity of 699.3mg/g was obtained at optimum conditions, which was closed to the experimental adsorption capacity of 703.57 mg/g. The adsorption phenomena was well represented by the pseudo-second-order model (R2 = 0.9983). On the whole, it was clear that MX/Fe3O4 has lot of potential as a Hg(II) ion impurity removal agent in aqueous solutions.

Development and Characterization of Biosorbent Film from Eggshell/Orange Waste Enriched with Banana Starch.

The conversion of waste into a valuable product is regarded as a promising alternative to relieving the burden of solid waste management and could be beneficial to the environment and humans. This study is focused on utilizing eggshell and orange peel enriched with banana starch to fabricate biofilm via the casting technique. The developed film is further characterized by field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The physical properties of films, including thickness, density, color, porosity, moisture content, water solubility, water absorption, and water vapor permeability, were also characterized. The removal efficiency of the metal ions onto film at different contact times, pH, biosorbent dosages, and initial concentration of Cd(II) were analyzed using atomic absorption spectroscopy (AAS). The film's surface was found to have a porous and rough structure with no cracks, which can enhance the target analytes interactions. EDX and XRD analyses confirmed that eggshell particles were made of calcium carbonate (CaCO3), and the appearance of the main peak at 2θ = 29.65° and 2θ = 29.49° proves the presence of calcite in eggshells. The FTIR indicated that the films contain various functional groups, such as alkane (C-H), hydroxyl (-OH), carbonyl (C=O), carbonate (CO32-), and carboxylic acid (-COOH) that can act as biosorption materials. According to the findings, the developed film exhibits a notable enhancement in its water barrier properties, thereby leading to improved adsorption capacity. The batch experiments showed that the film obtained the maximum removal percentage at pH = 8 and 6 g of biosorbent dose. Notably, the developed film could reach sorption equilibrium within 120 min at the initial concentration of 80 mg/L and remove 99.95% of Cd(II) in the aqueous solutions. This outcome presents potential opportunities for the application of these films in the food industry as both biosorbents and packaging materials. Such utilization can significantly enhance the overall quality of food products.

A novel four-chamber flow electrode capacitive deionization system for continuous recovery of heavy metal ions from wastewater

In view of the pollution of heavy metals to the environment and the importance for the industrial production, the removal and recovery of heavy metals from various water system is of great importance. In this study, a novel four-chamber flow electrode capacitive deionization (F-FCDI) process is constructed and successfully applied to the removal and recovery of heavy metal ions. Compared with conventional flow electrode capacitive deionization (FCDI) system, the F-FCDI system exhibits higher salt removal efficiency, faster salt removal rate, and lower energy consumption. The effect of different operating parameters on the removal efficiency of copper ions by F-FCDI system is studied, including the initial metal ions concentrations, the applied voltage, and the activated carbon content. The enrichment performance of the constructed F-FCDI system was evaluated under the optimal conditions (applied voltage 1.2 V, 5 wt% activated carbon content). 2000 mL Cu2+ solution with initial concentration 100 ppm was recycled in the F-FCDI system for 48 h and successfully enriched to 50 mL of concentrate solution. The enrichment factors reached 28.5 times, and the removal and enrichment of Cu2+ were realized synchronously. The removal efficiency of some other metal ions, like Ca2+, Mg2+, Pb2+, Cd2+, Co2+ was also evaluated. The removal efficiency can also reach more than 90% in F-FCDI system (initial concentrations 100 ppm). This study provides reference value for the removal and recovery of heavy metal ions in the future.

Reduction of cadmium content in 29 % and 54 % P2O5 phosphoric acid by manganese oxide material birnessite-type Na-MnO2

This paper presents a new approach for the purification of 29% and 54% P2O5 phosphoric acid contaminated with cadmium ions using synthesized lamellar material based on manganese (Na-MnO2). The removal efficiencies of cadmium ions were 35 % and 31 % for 54% and 29% P2O5 phosphoric acid. The kinetic and isotherm studies of cadmium adsorption were performed. After the phosphoric acid purification process, Na-MnO2 material was characterized by XRD, SEM, and TGA-DTA. All the results enable the refinement of the final phase by the Rietveld method. A proposed mechanism of cadmium ion removal by Na-MnO2 was given. The stability of the material was also controlled in the acid medium 29 % and 54 % P2O5. The results confirmed that Na-MnO2 material could be a potential sorbent for the efficient removal of heavy metals from phosphoric acid solutions. This simple process can be further developed and thus opens an avenue in the industrial sector to process larger quantities using high-performance materials based on manganese. Self-consistent ab initio calculations, based on DFT (Density Functional Theory) approach and using the FLAPW method (Full potential Linear Augmented Plane Wave), were performed to investigate both the electronic and magnetic properties of materials.

Cd+2 SORPTION FROM AQUEOUS SOLUTION USING ROSEMARY PLANT: PERFORMANCE AND ISOTHERM STUDY

This research was conducted to verify the removal efficiency of cadmium ions from an aqueous solution using a low-cost natural adsorbent. Rosemary plant was used in a batch system, and to understand this process more, several factors were investigated as follows: pH, contact time, initial metal ions concentration, amount of adsorbent material, and agitation speed. All experiments were carried out at room temperature. Whereas, the results showed the optimal value of removal was 83% for cadmium onto rosemary plant, under optimum operating conditions: pH 5, the adsorbent material dosage 2 g/100 ml, contact time 60 min, the metal concentration 10 mg/L, and agitation speed 250 rpm. The Freundlich adsorption isotherm model fits the equilibrium adsorption data for Cd+2better than the Langmuir model. This study found that the rosemary plant as a cost-effective and locally adsorbent for removing Cd+2from polluted water is efficient. Thus, it is possible to use the rosemary plant as a low-cost material to be used to adsorb heavy metals from wastewater.

Cyanidiales-Based Bioremediation of Heavy Metals.

With growing urbanization and ongoing development activities, the consumption of heavy metals has been increasing globally. Although heavy metals are vital for the survival of living beings, they can become hazardous when they surpass the permissible limit. The effect of heavy metals varies from normal to acute depending on the individual, so it is necessary to treat the heavy metals before releasing them into the environment. Various conventional treatment technologies have been used based on physical, chemical, and biological methods. However, due to technical and economic constraints and poor sustainability towards the environment, the use of these technologies has been limited. Microalgal-based heavy metal removal has been explored for the past few decades and has been seen as an effective, environment-friendly, and inexpensive method compared to conventional treatment technology. Cyanidiales that belong to red algae have the potential for remediation of heavy metals as they can withstand and tolerate extreme stresses of heat, acid salts, and heavy metals. Cyanidiales are the only photosynthetic organisms that can survive and thrive in acidic mine drainage, where heavy metal contamination is often prevalent. This review focuses on the algal species belonging to three genera of Cyanidiales: Cyanidioschyzon, Cyanidium, and Galdieria. Papers published after 2015 were considered in order to examine these species' efficiency in heavy metal removal. The result is summarized as maximum removal efficiency at the optimum experimental conditions and based on the parameters affecting the metal ion removal efficiency. This study finds that pH, initial metal concentration, initial algal biomass concentration, algal strains, and growth temperature are the major parameters that affect the heavy metal removal efficiency of Cyanidiales.