Removal of chromium from industrial waste by using eucalyptus bark

Several low cost biomaterials such as baggase, charred rice husk, activated charcoal and eucalyptus bark (EB) were tested for removal of chromium. All the experiments were carried out in batch process with laboratory prepared samples and wastewater obtained from metal finishing section of auto ancillary unit. The adsorbent, which had highest chromium(VI) removal was EB. Influences of chromium concentration, pH, contact time on removal of chromium from effluent was investigated. The adsorption data were fitted well by Freundlich isotherm. The kinetic data were analyzed by using a first order Lagergren kinetic. The Gibbs free energy was obtained for each system and was found to be -1.879 kJ mol(-1) for Cr(VI) and -3.885 kJ mol(-1) for Cr(III) for removal from industrial effluent. The negative value of deltaG0 indicates the feasibility and spontaneous nature of adsorption. The maximum removal of Cr(VI) was observed at pH 2. Adsorption capacity was found to be 45 mg/g of adsorbent, at Cr(VI) concentration in the effluent being 250 mg/l. A waste water sample containing Cr(VI), Cr(III), Mg, and Ca obtained from industrial unit showed satisfactory removal of chromium. The results indicate that eucalyptus bark can be used for the removal of chromium.     

Removal of hexavalent chromium using distillery sludge

Batch mode experiments were conducted to study the removal of hexavalent chromium from aqueous and industrial effluent using distillery sludge. Effects of pH, contact time, initial concentration and adsorbent dosage on the adsorption of Cr(VI) were studied. The data obeyed Langmuir and Freundlich adsorption isotherms. The Langmuir adsorption capacity was found to be 5.7 mg/g. Freundlich constants K(f) and n were 2.05 [mg/g(L/mg)(n)] and 3.9, respectively. Desorption studies indicated the removal of 82% of the hexavalent chromium. The efficiency of adsorbent towards the removal of chromium was also tested using chromium-plating wastewater.     

Heavy metals (Cd, Pb, Zn, Ni, Cu and Cr(III)) removal from water in Malaysia: post treatment by high quality limestone

This paper presents the results of research on heavy metals removal from water by filtration using low cost coarse media which could be used as an alternative approach to remove heavy metals from water or selected wastewater. A series of batch studies were conducted using different particle media (particle size 2.36-4.75 mm) shaken with different heavy metal solutions at various pH values to see the removal behaviour for each metal. Each solution of cadmium (Cd), lead (Pb), zinc (Zn), nickel (Ni), copper (Cu) and chromium (Cr(III)) with a concentration of 2 mg/L was shaken with the media. At a final pH of 8.5, limestone has significantly removed more than 90% of most metals followed by 80% and 65% removals using crushed bricks and gravel, respectively. The removal by aeration and settlement methods without solid media was less than 30%. Results indicated that the removal of heavy metals was influenced by the media and not directly by the pH. Investigations on the removal behaviour of these metals indicated that rough solid media with the presence of carbonate were beneficial for the removal process. Adsorption and precipitation as metals oxide and probably as metals carbonate were among the two mechanisms that contributed to the removal of metals from solution.     

The removal of chromium(VI) from aqueous solutions by Fagus orientalis L

The removal of chromium(VI) from aqueous solution under different conditions using an adsorbent was investigated. This adsorbent is Beech (Fagus orientalis L.) sawdust studied by using batch techniques. Batch studies indicated that the percent adsorption decreased with increasing initial concentration of chromium(VI). A contact time of 80 min was found to be optimum. Maximum chromium(VI) removal was observed near a pH of 1.0. Adsorption conformed to the Freundlich and Langmuir isotherms.     

Removal of chromium(VI) from water and wastewater using surfactant modified coconut coir pith as a biosorbent

Coconut coir pith, an agricultural solid waste was used as biosorbent for the removal of chromium(VI) after modification with a cationic surfactant, hexadecyltrimethylammonium bromide. Optimum pH for Cr(VI) adsorption was found to be 2.0. Reduction of Cr(VI) to Cr(III) occurred to a slight extent during the removal. Langmuir, Freundlich and Dubinin Radushkevich (D-R) isotherms were used to model the adsorption equilibrium data and the system followed all the three isotherms. The adsorption capacity of the biosorbent was found to be 76.3 mg g(-1), which is higher or comparable to the adsorption capacity of various adsorbents reported in literature. Kinetic studies showed that the adsorption obeyed second order and Elovich model. Thermodynamic parameters such as delta G0, delta H0 and delta S0 were evaluated, indicating that the overall adsorption process was endothermic and spontaneous. Effects of foreign anions were also examined. The adsorbent was also tested for the removal of Cr(VI) from electroplating effluent.     

Heavy metal adsorption properties of a submerged aquatic plant (Ceratophyllum demersum)

Heavy metals can be adsorbed by living or non-living biomass. Submerged aquatic plants can be used for the removal of heavy metals. In this paper, lead, zinc, and copper adsorption properties of Ceratophyllum demersum (Coontail or hornwort) were investigated and results were compared with other aquatic submerged plants. Data obtained from the initial adsorption studies indicated that C. demersum was capable of removing lead, zinc, and copper from solution. The metal biosorption was fast and equilibrium was attained within 20 min. Data obtained from further batch studies conformed well to the Langmuir Model. Maximum adsorption capacities (q(max)) onto C. demersum were 6.17 mg/g for Cu(II), 13.98 mg/g for Zn(II) and 44.8 mg/g for Pb(II). Kinetics of adsorption of zinc, lead and copper were analysed and rate constants were derived for each metal. It was found that the overall adsorption process was best described by pseudo second-order kinetics. The results showed that this submerged aquatic plant C. demersum can be successfully used for heavy metal removal under dilute metal concentration.     

Zinc has ambiguous effects on chromium (VI)-induced oxidative stress and apoptosis

Zinc is an important cellular antioxidant. We investigated its role in chromium-induced oxidative stress and apoptosis in human tumor cell line Hep-2. The measured parameters included intracellular labile zinc content (Zinquin-E fluorescence), cell viability (WST-1 assay), oxidative stress (spectrophotometry), mitochondrial potential (flow cytometry), caspase-3 activity, and PARP cleavage (immunofluorescence). We found that Hep-2 cells contain abundant labile zinc stores that may be depleted by the ionophore TPEN or increased by external zinc supplementation. Chromium (VI)-induced cytotoxicity and apoptosis were enhanced in zinc-depleted cells after 24 h, in particular at chromium (VI) concentrations of 50 and 150 micromol/l. On the other hand, elevated levels of labile zinc were able to protect against apoptosis induced by 10 micromol/l chromium (VI) but at higher chromium (VI) concentrations (50 and 150 micromol/l) acted synergistically, significantly enhancing oxidative stress and the course of apoptosis, possibly through oxidative stress and mitochondrial damage.     

一株耐铅、锌、铬菌株的分离鉴定及其吸附能力

【背景】采矿带来的土壤重金属污染问题对生态环境和人类健康产生了极大的危害,因此矿区重金属污染问题亟待解决。生物修复法成本低、资源广、没有二次污染,是修复土壤重金属污染的有效途径。【目的】以山东省曲阜市某煤矸石山周围土壤为材料,采用平板划线法分离筛选一株同时对铅、锌、铬有高耐性且吸附能力强的菌株。【方法】通过形态学特征、生理生化鉴定、分子生物学方法鉴定菌种;采用原子吸收分光光度计测量各重金属的浓度。【结果】鉴定菌株为蜡状芽孢杆菌(Bacillus cereus),命名为Bacillus cereus MZ-11。菌株MZ-11在pH为5.5-8.5、温度为15-45°C、NaCl质量分数为2%-8%时可正常生长。菌株MZ-11最高耐铅、锌、铬浓度高达1 000、1 200、1 600 mg/L。在培养基中铅、锌、铬3种重金属浓度分别为初始浓度(含Pb2+、Zn2+、Cr6+浓度分别为50、60、80 mg/L)、初始浓度的5倍、10倍、20倍的条件下,MZ-11对Cr6+和Zn2+的吸附比例则随浓度的提高逐渐增大,吸附百分比均在98%-99%以上。对Pb2+的吸附比例有一个最高值,并且P...     

Sequestration Enhancement of Metals in Soils by Addition of Iron Oxides Recovered from Coal Mine Drainage Sites

Iron oxides recovered from abandoned coal mine drainage (AMD) sites (Lowber, Scrubgrass, and Horner) as a soil amendment were investigated in this laboratory study for their effectiveness in the stabilization of cadmium, copper, and zinc in two metal-contaminated soils. The adsorption experimental results demonstrated that all three AMD iron oxides possess significant capacity for adsorption of Cd(II), Cu(II), and Zn(II). Horner iron oxide exhibited the highest adsorption capacity. Both the adsorption and the extraction experimental results showed metal sequestration enhancement through addition of Horner iron oxide to soil (5% to 50% by weight). With soil pH of 4.5 to neutral range, AMD iron oxide addition worked best for strongly adsorbed metals such as Cu, not so well for more weakly adsorbed metals such as Cd and Zn. The more AMD iron oxide amendment added, the less the mobility of the cationic target metals. Addition of AMD iron oxide for metal sequestration was more effective for the contaminated soils with low organic content.     

Effect of Rhamnolipids on Chromium-Contaminated Kaolinite

Hexavalent chromium Cr(VI) is a common environmental pollutant that is treated by its reduction to the trivalent form Cr(III). The latter can be re-oxidized to the toxic form, Cr(VI), under specific conditions. A study was conducted on the removal of Cr(III) to eliminate the hazard imposed by its presence in soil as there has been some evidence that organic compounds can decrease its sorption. The effect of addition of negatively-charged biosurfactants (rhamnolipids) on chromium contaminated kaolinite was studied. Results showed that the rhamnolipids have the capability of extracting 25% portion of the stable form of chromium, Cr(III), from the kaolinite, under optimal conditions. The removal of hexavalent chromium was also enhanced compared to water by a factor of 2 using a solution of rhamnolipids. Results from the sequential extraction procedure showed that rhamnolipids remove Cr(III) mainly from the carbonate and oxide/hydroxide portions of the kaolinite. The rhamnolipids had also the capability of reducing close to 100% of the extracted Cr(VI) to Cr(III) over a period of 24 days. This study indicated that rhamnolipids could be beneficial for the removal or long–term conversion of chromium Cr(VI) to Cr(III).     

Hexavalent chromium removal from aqueous solutions by a novel powder prepared from Colocasia esculenta leaves

In this study, batch removal of hexavalent chromium from aqueous solutions by powdered Colocasia esculenta leaves was investigated. Batch experiments were conducted to study the effects of adsorption of Cr(VI) at different pH values, initial concentrations, agitation speeds, temperatures, and contact times. The biosorbent was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectrometer analysis. The biosorptive capacity of the adsorbent was dependent on the pH of the chromium solution in which maximum removal was observed at pH 2. The adsorption equilibrium data were evaluated for various adsorption isotherm models, kinetic models, and thermodynamics. The equilibrium data fitted well with Freundlich and Halsey models. The adsorption capacity calculated was 47.62 mg/g at pH 2. The adsorption kinetic data were best described by pseudo-second-order kinetic model. Thus, Colocasia esculenta leaves can be considered as one of the efficient and cheap biosorbents for hexavalent chromium removal from aqueous solutions.     

Heavy metal biosorption by biomass of Ochrobactrum anthropi producing exopolysaccharide in activated sludge

The removal of chromium, cadmium and copper, toxic metals of high environmental priority due to their toxicity, from dilute aqueous solutions has been studied in the present work, applying a dead exopolysaccharide producing bacterium, Ochrobactrum anthropi, isolated from activated sludge. Particularly, the effect of pH, metal concentration and the effects of contact time were considered. Optimum adsorption pH values of chromium(VI), cadmium(II) and copper(II) were 2.0, 8.0 and 3.0 respectively. Experimental results also showed the influence of initial metal concentration on the metal uptake for dried biomass. Both the Freundlich and Langmuir adsorption models were suitable for describing the short-term biosorption of chromium(VI), cadmium(II) and copper(II) by O. anthropi.     

Thermodynamic and breakthrough column studies for the selective sorption of chromium from industrial effluent on activated eucalyptus bark

Studies were carried out on adsorption of Cr(VI) on an adsorbent made from eucalyptus bark. Results revealed that sorption of chromium on activated eucalyptus bark (AEB) was endothermic in nature. Thermodynamic parameters such as the entropy change, enthalpy change and Gibb's free energy change were found out to be 100.97 J mol(-1)K(-1), 33 kJ mol(-1) and -0.737 kJ mol(-1), respectively. Industrial chrome effluent of different chromium concentration at different pH was used as feedstock for the fixed bed adsorption studies. When effluent was fed to the column at low pH of 2, the breakthrough volume increased significantly compared to effluent at higher pH of 4.85. The surface properties of sorbent were characterized by the Scanning electron microscopy, X-ray diffraction technique and Infrared techniques. It was concluded that AEB sorbent column could be used effectively for removal of chromium from industrial effluents by reducing the pH of chrome effluent to two and at optimal column conditions.     

Modeling, simulation, and experimental validation for continuous Cr(VI) removal from aqueous solutions using sawdust as an adsorbent

Continuous adsorption experiments were performed in a fixed-bed adsorption column to evaluate the performance of low-cost adsorbent (sawdust) developed for the removal of Cr(VI) from aqueous solutions. The effects of influencing parameters such as flow rate, mass of adsorbent, initial Cr(VI) concentration were studied and the corresponding breakthrough curves were obtained. The fixed-bed adsorption process parameters such as breakthrough time, total percentage removal of Cr(VI), adsorption exhaustion rate and fraction of unused bed-length were obtained. A mathematical model for fixed-bed adsorption column was proposed by incorporating the effect of velocity variation along the bed-length in the existing model. Pore and solid diffusion models were used to describe the intra-particle mechanism for Cr(VI) adsorption. The proposed mathematical model was validated with the literature data and the experimental data obtained in the present study and the model was found to be good for explaining the behavior of breakthrough curves.     

Biosorption of chromium(VI) by spent cyanobacterial biomass from a hydrogen fermentor using Box-Behnken model

The study explores utilization of waste cyanobacterial biomass of Nostoc linckia from a lab-scale hydrogen fermentor for the biosorption of Cr(VI) from aqueous solution. The biomass immobilized in alginate beads was used for removal of the metal in batch mode optimizing the process conditions adopting response surface methodology (RSM). Kinetic studies were done to get useful information on the rate of chromium adsorption onto the cyanobacterial biomass, which was found to follow pseudo second-order model. Four important process parameters including initial metal concentration (10-100 mg/L), pH (2-6), temperature (25-45 °C) and cyanobacterial dose (0.1-2.0 g) were optimized to obtain the best response of Cr(VI) removal using the statistical Box-Behnken design. The response surface data indicated maximum Cr(VI) biosorption at pH 2-4 with different initial concentrations of the metal in the aqueous solution. The biosorbent could remove 80-90% chromium from solutions with initial metal concentration of 10-55 mg/L. Involvement of the surface characteristics of the biomass was studied through its scanning electron micrographs and Fourier transform infrared (FTIR) analysis.     

Potential use of green algae as a biosorbent for hexavalent chromium removal from aqueous solutions

The hexavalent chromium Cr(VI) poses a threat as a hazardous metal and its removal from aquatic environments through biosorption has gained attention as a viable technology of bioremediation. We evaluated the potential use of three green algae (Cladophora glomerata, Enteromorpha intestinalis and Microspora amoena) dry biomass as a biosorbent to remove Cr(VI) from aqueous solutions. The adsorption capacity of the biomass was determined using batch experiments. The adsorption capacity appeared to depend on the pH. The optimum pH with the acid-treated biomass for Cr(VI) biosorption was found to be 2.0 at a constant temperature, 45?°C. Among the three genera studied, C. glomerata recorded a maximum of 66.6% removal from the batch process using 1.0?g dried algal cells/100?ml aqueous solution containing an initial concentration of 20?mg/L chromium at 45?°C and pH 2.0 for 60?min of contact time. Langmuir and Freundlich isotherm equations fitted to the equilibrium data, Freundlich was the better model. Our study showed that C. glomerata dry biomass is a suitable candidate to remove Cr(VI) from aqueous solutions.     

The treatment of chromium tanning wastewater using natural marl

Abstract

The technical feasibility of removing chromium(III) from contaminated tannery wastewater by adsorption on naturally available marl, referred to as HEWAR in Palestine, has been investigated by batch experiments. The effects of various parameters on the percentage relative adsorption concentration were carried out by UV-vis spectrophotometry. Percentage relative concentration curves showed an increase with time until approaching a plateau (adsorption capacity). The adsorption capacity increased with the marl-to-liquid ratio, providing complete removal of chromium above 0.003g mL^?1 accomplished within 7 hours, while the marl particles were kept in suspension by stirring. The adsorption capacity increased with pH above 5.0, and decreased below this value. One sample of marl can be used for adsorbing chromium from various batches of wastewater until the adsorption sites are full.     

Removal of chromium on Polyalthia longifolia leaves biomass

Adsorption is an environmental friendly process for removal and/or recovery of heavy metals from wastewater. In recent years, it has been substantiated as a popular technique to treat industrial waste effluents, with significant advantages. In this work, batchwise removal of chromium (III) ions from water by Polyalthia longifolia leaves was studied as a function of adsorbent dose, pH, contact time, and agitation speed. Surface characteristics of the leaves were evaluated by recording IR spectra. The Langmuir, Freundlich, and Temkin adsorption isotherms were employed to explain the sorption process. It was found that one gram of leaves can remove 1.87 mg of trivalent chromium when working at pH 3.0. It has been concluded that Polyalthia longifolia leaves can be used as cost-effective and benign adsorbents for removal of Cr(III) ions from wastewater.     

Studies on the Performance of Ethylamine-Modified Chitosan Carbonized Rice Husk Composite Beads for Adsorption of Metal Ion

Heavy metals in the soil and ground water have endangered our environment and human bodies by direct or indirect pathways. Currently, bioremediation is a developing process that offers the possibility to destroy various contaminants using natural biological activity. Biopolymers are industrially attractive because of their capability of lowering transition metal ion concentrations to parts per billion, they are widely available, and they are environmentally safe. This paper deals with the preparation of an ethylamine-modified biopolymer (chitosan) and carbon from biowaste (rice husk) composite beads (EAM-CCRCB) for metal ion removal. The prepared adsorbent was used for the adsorption of hexavalent chromium ions from aqueous solutions. The activation and surface properties of the adsorbent were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analyses. The effect of process variables such as initial metal ion concentration, adsorbent dosage, and pH of the solution on the performance of percentage removal and adsorption capacity were studied. Various isotherm and kinetic models were fitted with experimental data to describe the solute interaction and nature of adsorption with the adsorbent through batch studies. Mass thermodynamic parameters were determined. Regeneration studies were attempted to check the stability and activity of the adsorbent.     

Removal of sulphate, COD and Cr(VI) in simulated and real wastewater by sulphate reducing bacteria enrichment in small bioreactor and FTIR study

The present study was conducted to investigate the chromium(VI), COD and sulphate removal efficiency from aqueous solution and treatment of real effluent (CETP) in a small scale bioreactor using sulphate reducing bacteria consortium. Effect of different hydraulic retention times (HRTs), initial metal concentrations, various carbon sources and temperatures were studied on removal of chromium(VI), COD and sulphate. Maximum chromium(VI) and sulphate removal was found to be 96.0% and 82.0%, respectively, at initial concentration of 50 mg l⁻¹ using lactate as carbon source. However, highest COD removal was 36.2% in medium containing fructose as the carbon source and electron donor. NADH dependent chromate reductase activity was not observed which indicated the anaerobic consortium. Initially consortium medium with a strong negative oxidation reduction potential indicated the reducing activity. The FTIR spectrum of the sulphate reducing bacteria consortium clearly shows the existence of the sulphate ions and signifies that sulfate reducing bacteria have used sulfate during the growth phase.