A review on applicability of naturally available adsorbents for the removal of hazardous dyes from aqueous waste

The effluent water of many industries, such as textiles, leather, paper, printing, cosmetics, etc., contains large amount of hazardous dyes. There is huge number of treatment processes as well as adsorbent which are available for the processing of this effluent water-containing dye content. The applicability of naturally available low cast and eco-friendly adsorbents, for the removal of hazardous dyes from aqueous waste by adsorption treatment, has been reviewed. In this review paper, we have provided a compiled list of low-cost, easily available, safe to handle, and easy-to-dispose-off adsorbents. These adsorbents have been classified into five different categories on the basis of their state of availability: (1) waste materials from agriculture and industry, (2) fruit waste, (3) plant waste, (4) natural inorganic materials, and (5) bioadsorbents. Some of the treated adsorbents have shown good adsorption capacities for methylene blue, congo red, crystal violet, rhodamine B, basic red, etc., but this adsorption process is highly pH dependent, and the pH of the medium plays an important role in the treatment process. Thus, in this review paper, we have made some efforts to discuss the role of pH in the treatment of wastewater.     

Fish Bone as a Low-Cost Adsorbent for Dye Removal from Wastewater: Response Surface Methodology and Classical Method

This research studied the application of fish bone as a low-cost adsorbent for the removal of two basic dyes (C.I. Basic Blue 41 and C.I. Basic Yellow 28) from textile wastewaters. The surface morphology and functional groups of the fish bone was studied by scanning electron microscopy and Fourier transform infrared, respectively. The experiments were designed in two methods: classical method and response surface methodology (RSM). The effect of operating parameters including pH, initial dye concentration, adsorbent dosage, and inorganic salts was investigated by both methods. The optimum conditions to satisfy 75 % of dye removal for both dyes were predicted by RSM method and the results were very close to the experimental values. So, it was concluded that the fish bone can be used as a low-cost adsorbent for dye removal from effluents.     

Dye removal using modified copper ferrite nanoparticle and RSM analysis

In this paper, copper ferrite nanoparticle (CFN) was synthesized, modified by cetyl trimethylammonium bromide, and characterized. Dye removal ability of the surface modified copper ferrite nanoparticle (SMCFN) from single system was investigated. The physical characteristics of SMCFN were studied using Fourier transform infrared, scanning electron microscopy, and X-ray diffraction. Acid Blue 92, Direct Green 6, Direct Red 23, and Direct Red 80 were used as model compounds. The effect of operational parameters (surfactant concentration, adsorbent dosage, dye concentration, and pH) on dye removal was evaluated. Response surface methodology (RSM) was used for the analysis of the dye removal data. The experimental checking in these optimal conditions confirms good agreements with RSM results. The results showed that the SMCFN being a magnetic adsorbent might be a suitable alternative to remove dyes from colored aqueous solutions.     

有机改性对凹凸棒黏土吸附四环素类抗生素的影响

采用OECD guideline 106批量平衡吸附法研究四环素类抗生素在十六烷基三甲基溴化铵改性凹凸棒黏土(CTAB-ATP)上的吸附作用,并考察了溶液pH、吸附剂的投加量、离子强度对吸附过程的影响。结果表明,CTAB-ATP对四环素、土霉素、金霉素3种四环素类抗生素的吸附容量随着溶液pH的增加而增加;随着吸附剂投加量的增大而减小;随着离子强度的增加呈现缓慢减小的趋势。CTAB-ATP对四环素、土霉素、金霉素的吸附过程均符合准二级动力学模型(r0.998),吸附等温线较好地符合Langmuir等温式。有机改性凹凸棒黏土的疏水性增强,提高了对有机污染物的吸附能力,其沉降性能良好,这使其作为一种吸附剂用于实际抗生素废水的处理成为可能。     

Adsorption characteristics of a phenoxy acetic acid herbicide on activated carbon

The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) by two powdered coal activated carbons was studied in aqueous solution. The modelling of the adsorption equilibrium showed that the adsorption of 2,4-D fitted a Langmuir isotherm. Adsorption was influenced by the activated carbon type, adsorbent concentration and solution characteristics. The adsorption was found to decrease with an increase in pH over the range 1.5-9. Maximum adsorption occurred at pH approximately 2.5, which corresponds to the 2,4-D pKa value. The amount of 2,4-D adsorbed was also found to depend on the NaCl concentration.     

Kinetic parameters for the removal of lead and chromium from wastewater using activated carbon developed from fertilizer waste material

The waste slurry generated in fertilizer plants in India has been converted into a cheap carbonaceous adsorbent material. The prepared adsorbent has been characterised and used for the removal of lead and chromium metals. The kinetics of adsorption and the extent of adsorption at equilibrium are dependent on the physical and chemical characteristics of the adsorbate, adsorbent and experimental system. Results of laboratory scale studies conducted to delineate the effect of such parameters on the kinetics of adsorption of metal ions are reported. Parameters evaluated include: hydronium ion concentration, temperature, initial adsorbate concentration, size of adsorbent, and amount of adsorbent. On the basis of these studies the various physical parameters such as effective diffusion coefficient, activation energies and entropy of activation are evaluated, as these provide some information regarding the mechanistic aspects. Mass transfer coefficient values suggest a rapid transport of the adsorbate from bulk to solid phase.     

Optimization of pulp mill effluent treatment with catalytic adsorbent using orthogonal second-order (Box-Behnken) experimental design

Novel catalytic adsorbent (ruthenium on carbon) was employed for the treatment of pulp mill effluent in the presence of hydrogen peroxide. Mathematical model and optimization of the process regarding the most favorable COD (%), TOC (%) and color (%) removal rates was developed and performed with experimental design taking into account catalytic adsorption process kinetics. As the initial experimental design, 3(3-1) half-fractional factorial design (H-FFD) was accomplished at two levels to study the significance of the main effects, such as catalytic adsorbent (g l(-1)) and hydrogen peroxide (ppm) concentrations using the response surface methodology (RSM). Finally, a four factor-three coded level central composite design (CCD) with 28 runs was performed in order to fit a second-order polynomial model. Validation of the model was accomplished by different criteria including coefficient of determination and the corresponding analysis of variance. The achieved removal rates for TOC (up to 75%), COD (up to 73%) and color (up to 68%) were observed for the defined optimal conditions: 1g l(-1) of ruthenium on carbon, 7 ppm of hydrogen peroxide, pH = 4 and ambient temperature. The proposed method benefited significantly improved TOC, COD and color removal efficiency, regenerability and reusability of the catalytic adsorbent and unaltered initial pH of an effluent in comparison to traditional adsorption or oxidation processes.     

The potential of different bio adsorbents for removing phenol from its aqueous solution

The use of natural resources for the removal of phenol and phenolic compounds is being looked upon by researchers in preference to other prevailing methods. In the present study, different biosorbents, brown algae (Padina pavonia), fresh water macrophyta (Ceratophyllum demersum), and black tea residue, were tested as adsorbent for the removal of phenol from aqueous solutions. The optimum conditions for maximum adsorption in terms of concentration of the adsorbate and pH were identified. The results show that the initial concentration increases as the removal of phenol increases in C. demersum; in the case of the other two adsorbents, the initial concentration increases as the removal of phenol decreases, especially for an initial concentration lower than 100 and 1,000 μg/L for P. pavonia and black tea residue, respectively. Maximum percentage removal of phenol by each adsorbent is 77, 50.8, and 29 % for C. demersum, P. pavonia, and black tea residue, respectively. Also, the biosorption capacity was strongly influenced by the pH of the aqueous solution with an observed maximum phenol removal at pH of around 6–10. The first biosorbent (black tea residue) displays the maximum adsorption capacity at a pH of 10 with a percentage sorption capacity of 84 %; P. pavonia revealed a greater adsorption percentage at pH?10, reaching 30 %, while for C. demersum, the removal of phenol increases with the increase in initial pH up to 6.0 and decreases drastically with further increase in initial pH. The Freundlich, Langmuir, and Brauner–Emmet–Teller adsorption models were applied to describe the equilibrium isotherms. The results reveal that the equilibrium data for all phenol adsorbents fitted the Freundlich model which seemed to be the best-fitting model for the experimental results with similar values of coefficient of determination.     

Treatment of wastewater containing arsenic using Rhazya stricta as a new adsorbent

The effective removal of heavy metals from aqueous wastes is among the most important issues for many industrialized countries. Removal of arsenic (As) from aqueous solutions was studied using Rhazia stricta biomass. The batch experiments are carried out to investigate the effect of the significant process parameters such as pH, contact time, solute concentration and adsorbent dose. The optimum pH required for maximum adsorption was found to be 5. The equilibrium data for the adsorption of As(V) on R. stricta are tested with various adsorption isotherm models such as Langmuir, Freundlich, Tempkin and Generalized equation. Results indicate the following order to fit the isotherm: Langmuir (1 and 2)?>?Tempkin?>?Generalized form?>?Freundlich. A comparison of two kinetic models showed that our data fitted well to the Elovich model.     

硝酸镧改性聚丙烯酸对水中氟离子的吸附试验探讨

以丙烯酸为原料,乙二醇二甲基丙烯酸酯为交联剂制得聚丙烯酸树脂(PAA),用于制备表面粗糙、介孔丰富的镧(Ⅲ)改性聚丙烯酸复合树脂(La-PAA)。试验表明,当500 mg/L氟离子溶液pH值为5、吸附时间为300 min时,La-PAA对氟离子的去除率在90%以上。Langmuir方程能较好地拟合氟离子在La-PAA上的吸附等温线,最大吸附量为159.24 mg/g,吸附动力学过程符合准二级动力学方程。