Search

Excessive fluoride intake has been reported in many studies, which can lead to diseases such as autism, mental retardation, low birth weight, reproductive disorder, as well as dental and bone fluorosis. The potential risk assessment of fluoride intake for the health of people living in Fars Province, Iran, is investigated. Hence, 1700 drinking water samples were taken from April 2018 to March 2020 in four seasons in 29 cities of Fars Province and were analyzed. Non-carcinogenic health risks of exposure to fluoride through drinking water were evaluated. Moreover, the spatial distribution maps of fluoride and hazard quotient (HQ) risk index were prepared using GIS software. The results showed that the concentration of fluoride in the drinking water of the studied area was in the range of 0.086 to 2.61 mg/L. Accordingly, in 48.27% of the cities, fluoride was in the range below the national and international standards, 34.48% of the cities were in the permissible range of 0.5 to 1.5 mg/L, and 17.24% of the urban areas of the province had fluoride contents above the permissible range. Hazard quotient index had the health risk of HQ > 1 in 27.58% of children, 17.24% of teenagers, and 10.34% of adults in the urban areas of Fars Province. In the cities with HQ > 1, there was risk of diseases associated with excessive fluoride intake. Therefore, it is necessary to replace water supply sources in these cities.

A novel adsorbent with excellent adsorptive properties for fluoride was prepared through a green and cheap synthesis route. Populus caspica pruning wastes, a cheap agri-waste material, were reduced to multi-layer green graphene (MLG) and then post-modified to aluminum/iron modified multi-layer green graphene (AMLG and IMLG). Batch experiments revealed the effect of pH (3–11), contact time (0.5–12 h), and initial fluoride concentration (5–40 mg/L). The conversion of raw material to MLG increased the specific surface area about 120 times (from 4 to 475 m2/g). Furthermore, a significant improvement in zero points of charge (pHzpc) was attained for IMLG (7.1) and AMLG (8) compared with pristine MLG (4.3). Fluoride showed superior affinity to AMLG and IMLG compared with MLG. Fluoride removal increased gradually by pH from 3 to 8 and then decreased sharply up to pH 11. The study of process dynamics demonstrated the monolayer fluoride adsorption onto AMLG and IMLG controlled by the chemisorptions. The highest predicted adsorption capacities based on the Langmuir model were 31.52, 47.01, and 53.76 mg/g for MLG, IMLG, and AMLG, respectively. Considering economic and technical feasibility presents AMLG and IMLG as a promising candidate against water contamination by elevated fluoride.

Among cationic dyes, malachite green (MG) is commonly used for dying purposes and also as an inhibitor in aquaculture, food, health, and chemical industries due to its cytotoxic effects. Therefore, MG removal is essential to keep the ecosystem and human health safety. Adsorption is a viable and versatile option and exploring efficient adsorbents have high priority. Herein, MOF-5 and aminated corn Stover reduced graphene oxide (ACS-RGO) of typical adsorbents of metal–organic-frameworks (MOFs) and carbon-based classes were studied for MG removal. MOF-5 and ACS-RGO had a specific surface area and total pore volume of 507.4 and 389.0 m2/g, and 0.271 cm3/g and 0.273 cm3/g, respectively. ACS-RGO was superior for MG adsorption and the kinetic rate coefficient for ACS-RGO was ~ 7.2 times compared to MOF-5. For ACS-RGO, MG removal remained high (> 94%) in a wide range of pH. However, dye removal was pH-dependent for MOF-5 and increased from ~ 32% to ~ 67% by increasing pH from 4 to 12. Increasing dye concentration from 25 mg/L to 100 mg/L decreased adsorption by MOF-5 and ACS-RGO for ~ 30% and 7%, respectively. Dye removal was evident in a few tens of seconds after adding ACS-RGO at doses above 0.5 g/L. A significant loss of 46% in adsorption was observed by decreasing MOF-5 mass from 1 to 0.1 g/L. ACS-RGO removed MG in multilayer with an exceptional adsorption capacity of 1088.27 mg/g. In conclusion, ACS-RGO, and MOF-5 showed promising kinetic rates and adsorption capacities toward MG.

The presence of trace levels of pharmaceutically active compounds (PhACs) in the aquatic environment threatens human health and the environment. Metronidazole (MNZ) is a soluble PhAC with low biodegradability, a possible human mutant and carcinogen. This study aimed the synthesis, physicochemical characterizations, and employment of porous amine-modified green-graphene (AMGG) for MNZ removal from aqueous solutions. Response-surface methodology (RSM) based on Box-Benken design (BBD) was used to assess the MNZ adsorption efficiency of AMGG as a function of pH (4–12), contact time (5–60 min), AMGG dose (0.1–1 g/L) and MNZ concentration (10–100 mg/L). From the model optimization, the highest MNZ removal was predicted at a pH of 5.9, a contact time of 27 min, an AMGG dose of 0.86 g /L, and an MNZ concentration of 100 mg /L. The experimental data were in agreement with the pseudo-second order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity of AMGG for MNZ was 416.7 mg/g. The MNZ concentration at equilibrium increased about 4.8 mg/L when the solution temperature increased by 20 oC (from 30 to 50 °C), indicative of an exothermic process. AMGG showed an efficiency decrement from 84 % to 57 %, after five consecutive saturation-regeneration cycles. Moreover, AMGG showed a removal efficiency of 74 % when it was employed for real hospital wastewater treatment.

Excessive fluoride intake has been reported in many studies, which can lead to diseases such as autism, mental retardation, low birth weight, reproductive disorder, as well as dental and bone fluorosis. The potential risk assessment of fluoride intake for the health of people living in Fars Province, Iran, is investigated. Hence, 1700 drinking water samples were taken from April 2018 to March 2020 in four seasons in 29 cities of Fars Province and were analyzed. Non-carcinogenic health risks of exposure to fluoride through drinking water were evaluated. Moreover, the spatial distribution maps of fluoride and hazard quotient (HQ) risk index were prepared using GIS software. The results showed that the concentration of fluoride in the drinking water of the studied area was in the range of 0.086 to 2.61 mg/L. Accordingly, in 48.27% of the cities, fluoride was in the range below the national and international standards, 34.48% of the cities were in the permissible range of 0.5 to 1.5 mg/L, and 17.24% of the urban areas of the province had fluoride contents above the permissible range. Hazard quotient index had the health risk of HQ 1 in 27.58% of children, 17.24% of teenagers, and 10.34% of adults in the urban areas of Fars Province. In the cities with HQ 1, there was risk of diseases associated with excessive fluoride intake. Therefore, it is necessary to replace water supply sources in these cities.

A cost-effective and environment-benign adsorbent was prepared from an abundant agro-waste material. Wheat straw was reduced to graphene and then modified by crosslinking to epichlorohydrin. During the conversion process of wheat straw to graphene, the specific surface area increased more than 100 times (from 4 to 415 m2 g−1). The adsorption efficiency of raw wheat straw, graphene nanosheets, and modified graphene against Eriochrome Black T (EBT) were 8.0, 34.7, and 74.4%, respectively. The modified graphene was further investigated for the effect of environmental condition, i.e., pH (3 to 11), EBT concentration (25–100 mg L−1), adsorbent dosage (0.25–0.75 g L−1), contact time (5–60 min), and solution temperature (30–60 °C). The dye removal remained at a high level under a wide range of pH from 3 to 9. The EBT removal decreased from 87.3 to 54.5 by increasing dye concentration and increased from 38.2 to 85.4% by increasing adsorbent dose in the studied ranges. Dye removal also increased by mixing time from 5 to 30 min, whereas a slight drop was observed by continuing agitation up to 60 min. Conducting experiments at various temperatures revealed an endothermic process. Pseudo-first-order and pseudo-second-order models were adequate to represent the adsorption kinetics. Isotherm models suggest a multilayer adsorption of EBT molecules on heterogeneous modified graphene surface with a maximum adsorption capacity of 146.2 mg g−1. The present work demonstrated that the modified graphene obtained from available and low-cost agro-wastes could be used effectively as adsorbent against EBT from aqueous media.

BACKGROUND: The aim of this study was to investigate the removal of Cr (VI) using Green-Graphene Nanosheets (GGN) synthesized from rice straw. METHODS: Synthesis of the GGN was optimized using response surface methodology and central composite design (CCD). The effect of two independent variables including KOH-to-raw rice ash (KOH/RRA) ratio and temperature on the specific surface area of the GGN was determined. To have better removal of Cr (VI), GGN was modified using the grafting amine group method. In the Cr (VI) removal process, the effects of four independent variables including initial Cr (VI) concentration, adsorbent dosage, contact time, and initial solution pH were studied. RESULTS: The results of this study showed that the optimum values of the KOH/RRA ratio and temperature for the preparation of GGN were 10.85 and 749.61 °C, respectively. The maximum amount of SSA obtained at optimum conditions for GGN was 551.14 ± 3.83 m 2 /g. The optimum conditions for Cr (VI) removal were 48.35 mg/L, 1.46 g/L, 44.30 min, and 6.87 for Cr (VI) concentration, adsorbent dosage, contact time, and pH, respectively. Based on variance analysis, the adsorbent dose was the most sensitive factor for Cr (VI) removal. Langmuir isotherm (R2 = 0.991) and Pseudo-second-order kinetic models (R2 = 0.999) were the best fit for the study results and the Q max was 138.89 mg/g. CONCLUSIONS: It can be concluded that the predicted conditions from the GGN synthesis model and the optimum conditions from the Cr (VI) removal model both agreed with the experimental findings.

The objective of this work was to investigate the modification of soil contaminated with phenanthrene (PHE) by electro-kinetic remediation (EKR) process using response surface methodology (RSM). The soil sample was obtained from the subgrades (0–30 cm) of an area close to Shahroud City, Northeast of Iran. The effect of variables such as initial pH, voltage, electrolyte concentration, and reaction time on PHE removal was studied. Based on the results obtained from the central composite design (CCD) experiment, the highest and lowest amount of PHE removal was 97 and 20%, respectively. In this study, the variables A, B, C, AB, AC, and C2 with a p value < 0.05 were significant model terms and the parameter of the lack of fit was not significant (p value = 0.0745). Findings indicated that the “predicted R-squared” of 0.9670 was in reasonable agreement with the “adj R-squared” of 0.9857 and the plot of residual followed a normal distribution and approximately linear. Also, the kinetic rates of the removal PHE by the EKR process best fitted with a first-order kinetic model (R2: 0.926). Results of the investigation of the effective variables showed that in values of pH 3, time of 168 h, voltage of 3 V, and electrolyte concentration of 4 mg/L, the removal efficiency of PHE reached 96.6%.

A green synthesis approach was conducted to prepare amine-functionalized bio-graphene (AFBG) as an efficient and low cost adsorbent that can be obtained from agricultural wastes. In this study, bio-graphene was successfully used to remove Ciprofloxacin (CIP) from synthetic solutions. The efficacy of adsorbent as a function of operating variables (i.e. pH, time, AFBG dose and CIP concentration) was described by a polynomial model. A optimal99.3% experimental removal was achieved by adjusting the mixing time, AFBG dose, pH and CIP concentration to 58.16, 0.99, 7.47, and 52.9, respectively. Kinetic model revealed that CIP diffusion into the internal layers of AFBG controls the rate of the process. Furthermore, the sorption process was in monolayer with a maximum monolayer capacity of 172.6 mg/g. Adsorption also found to be favored under higher CIP concentrations. The thermodynamic parameters (ΔG°0, and ΔS°>0) demonstrated that the process is endothermic and spontaneous in nature. The regeneration study showed that the AFBG could simply regenerated without significant lost in adsorption capacity.

Fly ash were successfully modified by a chemical method (iron and aluminum salts and surfactant) with the aim of removing Cr(VI) from aqueous solution. In this study, response surface methodology (...

Activated carbon was successfully prepared from Populous caspica wood by a thermochemical reduction method and modified by grafting amine groups. In the batch tests, pH, initial phosphate concentration, reaction time, and adsorbent dose were evaluated to remove phosphate (PO43-) from the aqueous phase. The response surface method was chosen to study the composition effect of independent input factors and one dependent output response (removal efficiency). The p-value (2.2 x 10(-16 )), F-value (116.6), R-2 (multiple: 0.9774, adjusted: 0.97), and lack of fit (0.167) indicated that the reduced quadratic model is highly significant for the phosphate removal using aminated activated carbon. The maximum efficiency removal of phosphate (92.76) was obtained at pH, initial phosphate concentrations, contact time, and adsorbent dose of 3, 10 mg L-1, 60 min, and 90 mg L-1, respectively. The adsorption data fitted well with the Freundlich isotherm and pseudo-second-order kinetic model. Therefore, the intraparticle diffusion was the dominant adsorption mechanism but it was not the sole rate controlling step. In addition, regeneration process with five repetitions of regeneration cycles showed high desorption efficiencies and slight loss of spent adsorbent initial adsorption capacity. Thus, the results recommended that modified activated carbon prepared from agricultural waste (P. caspica) could properly remove phosphate from aqueous solution.

In this article, bio-graphene nanosheet was prepared using an agricultural waste and converted to a weak base anionic exchanger. Anionic bio-graphene nanosheet structural characteristics and exchanger capacity for nitrate removal from aqueous solution and optimizations of various experimental parameters were evaluated. Nitrate adsorption was done with developing prediction model using the response surface methodology. In addition, regeneration rate was evaluated with eluting HCl (0.1 mol/L) solution. The results of the removal model disclosed that initial concentration of nitrate had reverse effects on the nitrate removal and the effects of other variables (adsorbent dose, contact time and pH) at the pH of zero-point charge was direct. The adsorption data obtained from experiments were in line with the pseudo-second-order kinetic (R2 = 0.998) and Langmuir isotherm (R2 = 0.943). Based on the Langmuir model, the maximum adsorption capacity (Qmax) for nitrate removal by anionic bio-graphene nanosheet was 182.506 mg/g at 150 mgNO3−/L. The results of thermodynamic study showed that the enthalpy change (ΔH°) and entropy change (ΔS°) were 867.97 (kJ/mol) and 3.1432 (J/mol·K), respectively. Also, according to the results, the main mechanism of nitrate adsorption onto the anionic bio-graphene was ion exchange. In addition, regeneration process with 4 repetitions of consecutive adsorptions–regeneration cycles showed high desorption efficiencies and slight losses in its initial adsorption capacity.

Introduction and purpose: The need to access and produce clean water is currentlyfelt more than ever by the communities due to the pollution of drinking watersources and the consumers’ growing concern and awareness about the absence ofhealthy drinking water. As a result, in the recent years, the use of water purificationsystems has been widely increased in the urban and rural regions of Iran. Regardingthis, the aim of the present study was to investigate the causes of the tendency to usehome desalination systems in the households of Bandar Lengeh, Hormozgan, Iran.Methods: This descriptive, cross-sectional study was conducted on 140 householdsin the fall of 2014. The study population was selected through simple randomsampling technique. The data were collected using a questionnaire enquiring thecause of using home desalination systems among the people living in BandarLengeh. Data analysis was performed in SPSS, version 24 using Chi-square test.Results: According to the results of the present study, none of the investigatedhouseholds directly used the water distributed in the city for drinking. Only 12.9%of the households used this water for cooking. Therefore, the water distributed inthe urban network was mostly used for irrigation as well as washing dishes andclothes. Furthermore, the most frequently reported reasons for the non-use of thewater were discoloration of tea and slowing down the cooking of food.Conclusion: As the findings of the present study indicated, it is not essential touse the domestic purification systems. Accordingly, the tendency to use thesesystems are mainly raised by incorrect beliefs about this issue. This highlightsthe necessity of implementing educational programs targeting toward theimprovement of the households’ awareness regarding the health issues.

Various Zeolitic Imidazolate Frameworks (ZIFs), a unique class of metal organic frameworks (MOFs), were prepared and studied for the removal efficiency against the hazardous azo dye eriochrome black-T (EBT) from water. Two type of ZIF were synthesized, Co-based (ZIF-67) and Zn-based (ZIF-8). For each type, four variations with different morphologies were chosen in order to determine the best performing candidate for the further optimization studies. ZIF-67-OAc showed a superior adsorptive EBT removal efficiency compared to the rest herein studied ZIFs. To statistically model the EBT removal, response surface methodology (RSM) using Box-Behnken design (BBD) technique was followed. According to the model, solution/suspension pH was found to play the most significant role that govern the rate of EBT adsorption. Under optimized condition, where pH, ZIF-67-OAc dose, mixing time, and EBT concentration set to be 6.82, 832.4 mg/L, 39.95 min, and 100 mg/L, respectively, a 99 % EBT removal was achieved. The equilibrium data best fitted to Freundlich isotherm model, indicating that the dye molecules accumulate in multilayer on the ZIF-67-OAc surface. Based on the Langmuir isotherm model that was also fitted well (R2 = 0.95), the qmax was found 263.5 mg/g. Furthermore, EBT adsorption onto ZIF-67-OAc was descripted better with the pseudo-first order kinetic model.

There is an urgent demand to abate contamination of the water resources and wastewaters from antibiotics, released predominately from the municipal and healthcare effluents. Herein, we modified an eco-friendly and renewable agro-waste/biomass material in order to obtain an efficient adsorbent against the antibiotic tetracycline hydrochloride (TC). Corn stover biomass was thermally converted to porous reduced graphite oxide (RGO) and then was post functionalized to an aminated graphitic carbonaceous material (ACS-RGO). The materials were characterized by nitrogen adsorption/desorption, scanning electron microscopy (SEM), transmission electron microscope (TEM), as well as Raman and FTIR spectroscopy. The sorption process was statistically modeled, by systematically varying crucial factors, based on Box–Behnken design (BBD). The model analysis illustrated the effect of independent variables and their correlations in order to determine the optimum parameters/conditions. The highest TC removal (100%) was found to occur for initial TC concentration of 48.74 mg/L, 0.98 gL dosage of adsorbent, 51.6 min contact time and at pH = 7.4. The maximum monolayer adsorption capacity estimated to be 132.9 mg of TC per gram of ACS-RGO.

Frying food is one of the most admired methods to make instant cuisine among people because of its taste and color, as well as the crispy texture creation. Hydrogen peroxide which is the result of frying, causes various diseases, including cancer, atherosclerosis, cardiac and cerebral ischemia, aging and liver disorders. Therefore, this study aims to investigate the amount of peroxide in the oils used in bistros in western Iran. This descriptive cross-sectional study carried out in the restaurants in western Iran. In this study, 81 samples of consumable oils gathered according to the standard of 493 Iranian Institute of Standards and Industrial Research. After transferring the samples to the laboratory, there peroxide value was measured according to the standard number 4179 and data was entered in Excel and SPSS version 16 for further analyses. Out of 81 samples, 59% (48 samples) from consumable samples at the standard level and 41% (33 samples) of the non-consumable samples higher than the standard rate of the Institute of Standards and Industrial Research of Iran. While cooking, the consumable oil average peroxide value was 5.72, without a night and day breakdown (in general). In addition, the lowest and highest peroxide oxidation was 0 and 29 mEq/kg. According to Mann-Whitney test, there was no significant difference between the amounts of peroxide in consumable oils. Some evidence shows the non-compliance with hygiene issues that are related to oil consumption. This requires more supervision and continuous sampling and testing. © 2018, Advanced Scientific Research. All rights reserved.

At present, nanofiltration (NF) technologies find the ever greater use in the water industry, particularly, drinking water supplies. The concentrations of most anions in the groundwater sources are much higher than surface water and in some cases are higher than drinking water standards. In this regard, the aim of this study was to investigate the possibility of application of nanofilters in removing phosphate, fluoride, and nitrite from aqueous solutions. In this research, the effect of different factors including initial concentrations of nitrate, phosphate, and fluoride along with the flow rate were investigated. The results showed that with an increase in the initial concentrations of phosphate, fluoride, and nitrite, along with an increase in flow rate, the removal efficiencies decreased. The maximum removal efficiencies for phosphate, fluoride, and nitrite were 98, 82, and 87%, respectively. According to the findings, NF membrane could be recommended for removing nitrates, fluoride, and phos...

Dye wastewater produced from industrial activity is usually toxic, resistant to biodegradation and persistent in the environment. The aim of this study was to evaluate the efficiency of multiwalled carbon nanotubes (MWCNTs) for decolorization of Direct Blue 71 (DB71). In this experimental study, the effect of various variables including contact time, solution pH, adsorbent dose, and initial dye concentration was evaluated in a batch reactor. The adsorption and kinetic models were evaluated to explain the adsorbed dye and dynamic reaction. The results of this study showed that the efficiency of dye removal increased, as the contact time and adsorbent dose increased, but as pH and initial dye concentration increased, removal efficiency decreased. The maximum efficiency of Direct Blue 71 removal was observed at acidic solution (pH=3), contact time of 90 minutes, adsorbent dose of 0.6 g/l and initial dye concentration of 25 mg/l. The adsorption of direct blue 71 best fitted the Langmuir isotherm (R2=0.87) and pseudo first order kinetic equation (R2=0.99). According to the results obtained, multiwalled nanotubes was offered as an effective adsorbent for removing direct blue 71. © Authors.

Potential of granulated modified nanozeolites Y for MTBE removal from aqueous solutions: Kinetic and isotherm studies Adsorption of methyl tert-butyl ether (MTBE) from aqueous solutions by granulated modified nanozeolites Y was investigated. Nanozeolite Y powders were converted into granulated zeolites and subsequently modified with two cationic surfactants (20 mmol/dm3), to be used as adsorbent. Granulated nanozeolites were characterized by BET surface area analysis, elemental analysis and X-ray diffractometer. -Hexade-cyltrimethylammonium (HDTMA-Cl) modified granulated zeolite had more effective performance than N-cetylpyridinium bromide (CPB) modified granulated zeolite. The most conventional adsorption isotherms and kinetic models were applied to describe MTBE adsorption and reaction dynamic, respectively. The equilibrium sorption data fitted the Langmuir 2 isotherm model and the kinetic study was followed the pseudo-second-order model. The maximum adsorption capacities for HDTMA-Cl modified zeolite and CPB modified granulated zeolite were 333.33 and 142.8 mg/g, respectively as calculated by the Langmuir model. This study demonstrated that the removal of mtbe by granulated modified nanozeolites Y is a promising technique.

Monoaromatic hydrocarbons including benzene, toluene, ethylbenzene and xylene isomers (BTEX) are a very important category of water pollutants. These volatile compounds are very hazardous because of their fast migration in soil and water bodies and their acute and chronic toxicities when inhaled or ingested, especially benzene which is a known carcinogenic molecule. In this study, a natural zeolite (i. e., clinoptilolite-rich tuffs) was modified by two cationic surfactants (i. e., hexadecyltrimethyl ammonium chloride (HDTMA-Cl), and N-cetylpyridinium bromide (CPB)). The prepared adsorbents were then characterized, and their adsorptive capabilities for BTEX examined at different experimental conditions. The results of adsorption tests at 24 h revealed that the adsorption capacity of the modified zeolites improved by increasing the surfactant loading (i. e., less than the critical micelle concentration (CMC), to higher than the CMC), which caused an increase in sorption capacity from 60 to 70% for HDTMA-modified samples, and from 47 to 99% for CPB-modified zeolite. Adsorption kinetic tests showed the optimum contact time was 48 h with an average BTEX removal of 90 and 93% for HDTMA-modified and CPB-modified zeolite, respectively. Results showed that by increasing of pH from 3 to 11, the sorption capacity of the adsorbent decreased markedly from 97 to 75%. Analyzing the influence of temperature showed that the adsorption efficiency of adsorbents for benzene reduced from 93% at 20°C to 10% at 4°C. However, the influence of temperature on other compounds was not remarkable. Overall, CPB-modified zeolite exhibited higher selectivity toward BTEX compounds at optimum experimental conditions. Although commercial powder activated carbon (PAC) showed a higher capacity for all BTEX compounds and faster adsorption kinetics, the adsorption capacity of the CPB-modified zeolite at optimized conditions was competitive with PAC results.

Aims: The purpose of this study is to investigate the feasibility of the absorption of lead and cadmium from the leachate, by natural zeolite clinoptilolite and improving the zeolite ability by a modified surface. Materials and Methods: To examine the absorption ability of these two metals (lead and cadmium), the variables, such as, type of sorbent, sorbent concentration, and contact time were studied. Zeolite samples were analyzed by X-ray florescence, the spectrum of X-ray diffraction, and Brunauer-Emmett-Teller (BET). Results: The absorption efficiency of the modified zeolites were increased from 4.2 and 5.3 percent to 71.6 and 75.2 percent for lead and cadmium, respectively. With increasing the surfactant concentration from 2 to 20 mmol/L, the absorption efficiency of modified zeolite for lead and cadmium was increased to 71 and 74%, respectively. The best isotherm model for lead adsorption was Freundlich model, with a determination coefficient equal to 0.99, and for cadmium it was Langmuir model with a determination coefficient equal to 0.99. Conclusions: The modified zeolite with surfactant can be used as an appropriate adsorbent for the separation of heavy metals from waste Leachate. Lead and cadmium were absorbed in a single layer on the surface of the modified zeolite with surfactant, comparing different isoterm models, indicated that the capacity of the modified zeolite for lead adsorption was more than cadmium adsorption, but cadmium was absorbed with higher energy.

Aims: The aim of this study is the recovery of municipal refuse and using it as a biosorbent for Nickel (II) and Chromium (VI) (Ni 2+ an d Cr 6+ )removal from aqueous solutions. Materials and Methods: Activated sludge was obtained from the wastewater treatment plant in a dairy industry. All experiments were performed in the batch system and effective parameters such as the pH, adsorbent dosage, and the initial concentration and contact time of Ni 2+ and Cr 6+ were investigated. The adsorption isotherms and kinetics were evaluated to describe the metal uptake and dynamic reactions. Results: The results of this study showed that with an increasing adsorbent dose and contact time, Ni 2+ and Cr 6+ removal efficiency increased. The maximum adsorption of Ni 2+ and Cr 6+ was obtained in pH 6 and 2, respectively. Meanwhile, with increasing Ni 2+ and Cr 6+ concentration, the removal efficiency decreased. The results best fitted the Langmuir isotherm and the maximum absorption capacity of Ni 2+ and Cr 6+ onto dry activated sludge (DAS) were 2.17 and 2.23 mg/g, respectively. Analysis of the adsorption kinetics showed that the intraparticle diffusion kinetic had been good and presented Ni 2+ and Cr 6+ uptake onto DAS, and the intraparticle diffusion rate constant of Ni 2+ and Cr 6+ were 0.044 and 0.042 (mg/g min 0.5 ), respectively. Conclusions: According to the results, dry activated sludge is suggested as a low cost and available adsorbent for removing Ni 2+ and Cr 6+ from aqueous solutions.