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Dynamics of Potassium Release and Adsorption on Rice Straw Residue  [PDF]
Jifu Li, Jianwei Lu, Xiaokun Li, Tao Ren, Rihuan Cong, Li Zhou
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0090440
Abstract: Straw application can not only increase crop yields, improve soil structure and enrich soil fertility, but can also enhance water and nutrient retention. The aim of this study was to ascertain the relationships between straw decomposition and the release-adsorption processes of K+. This study increases the understanding of the roles played by agricultural crop residues in the soil environment, informs more effective straw recycling and provides a method for reducing potassium loss. The influence of straw decomposition on the K+ release rate in paddy soil under flooded condition was studied using incubation experiments, which indicated the decomposition process of rice straw could be divided into two main stages: (a) a rapid decomposition stage from 0 to 60 d and (b) a slow decomposition stage from 60 to 110 d. However, the characteristics of the straw potassium release were different from those of the overall straw decomposition, as 90% of total K was released by the third day of the study. The batches of the K sorption experiments showed that crop residues could adsorb K+ from the ambient environment, which was subject to decomposition periods and extra K+ concentration. In addition, a number of materials or binding sites were observed on straw residues using IR analysis, indicating possible coupling sites for K+ ions. The aqueous solution experiments indicated that raw straw could absorb water at 3.88 g g?1, and this rate rose to its maximum 15 d after incubation. All of the experiments demonstrated that crop residues could absorb large amount of aqueous solution to preserve K+ indirectly during the initial decomposition period. These crop residues could also directly adsorb K+ via physical and chemical adsorption in the later period, allowing part of this K+ to be absorbed by plants for the next growing season.
Preparation and Characterization of Activated Carbon from Rice Straw Pre-treated by the Subcritical Hydrolysis

DONG Yu,SHEN Zhe-min,LEI Yang-ming,WANG Qian,LIU Ting-ting,

环境科学 , 2012,
Abstract: Activated carbons were prepared from waste residue which was obtained from rice straw dealt with subcritical water by chemical activation with ZnCl2.It was also considered that the variations of activation temperature,activation time,impregnation time and impregnation ratio influenced the performance of activated carbon.Adsorption isotherm and scanning electron microscopy(SEM) were used to characterize the pore structure and surface morphology of carbon.Adsorption kinetics and isotherms of methylene blue,used here as a reference compound,were studied.The results show that when zinc chloride content was 20%,the optimum conditions of activated carbon produced are obtained-reaction temperatures of 900℃,activation time of 60 min,impregnation ratio of 1∶5 and impregnation time of 12 h.The number of iodine and methylene blue of activated carbon is 1 122.79 mg·g-1,136.50 mg·g-1,respectively.Adsorption of methylene blue on activated carbon fits the Langmuir equation and pseudo-second kinetic model can well describe the adsorption process of methylene blue.The negative change in free energy(ΔG0) and positive change in enthalpy(ΔH0) indicate that the adsorption is a spontaneous and endothermic process.
Journal of Applied Sciences in Environmental Sanitation , 2010,
Abstract: In this paper adsorption of Ce (IV) ion from aqueous solution using wood sawdust obtained from a local carpentry (termed as SD) as a very cheap and efficient adsorbent has been investigated. Radioisotopes of cerium are a common constituent of liquid radioactive wastes arising from nuclear facilities. So, the removal of cerium ions from the wastewater of nuclear plants is in great importance. Adsorption experiments were carried out using both batch and column systems. The influence of some important experimental conditions such as dosage of adsorbent, initial concentration, contact time has been investigated. In order to have a better comparison, the sorption capacity of sawdust was compared with a commercial grade of activated carbon. It was found that sawdust is a very efficient adsorbent for uptake of cerium ion from aqueous solutions such as nuclear power plants wastewaters.
Removal of Azo Dyes (Violet B and Violet 5R) from Aqueous Solution Using New Activated Carbon Developed from Orange Peel  [PDF]
Saeedeh Hashemian,Khaterah Salari,Hamila Salehifar,Zahra Atashi Yazdi
Journal of Chemistry , 2013, DOI: 10.1155/2013/283274
Abstract: Activated carbon developed from agricultural waste orange peel (COP) was prepared. COP was characterized using Fourier infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and BET. COP has surface area and mean pore diameter of 225.6?m2?g?1 and 22.40?nm, respectively. The removal of violet B (VB) and violet 5R (V5R) from aqueous solutions by COP was investigated. The effect of operational parameters such as contact time, pH, initial dye concentration, and adsorbent dosage on the adsorption of dyes was investigated. Maximum dye was removed within 30 min of contact time at pH > 7. Two common models, the Langmuir and Freundlich isotherms, were used to investigate the interaction of dye and COPs. The isotherm evaluations revealed that the Langmuir model provides better fit to the experimental data than the Freundlich model. The adsorption of VB and V5R onto COP was followed by pseudo-second-order kinetic model with a good correlation ( ). Activation energies 5.47 and 29.7?KJ?mol?1 were determined for violet B and violet 5R, respectively. The rate of adsorption of violet 5R was faster than that of violet B ( ). The prepared COP could thus be used as promising adsorbent for removal of organic dyes, especially azo dye, from polluted water. The solid COP could be conveniently regenerated after adsorption. 1. Introduction Many industries employ dyes and pigments to color their products. Most dyes are inert and nontoxic at the concentration discharged into the receiving water. Dyes are usually stable to photodegradation, biodegradation, and oxidizing agents [1]. Color removal from effluents is a major environmental problem because of difficulty of treating such streams by conventional physicochemical and biological treatment methods [2]. Many physical and chemical methods such as coagulation, precipitation, and oxidation have been used for dye removal from water [3]. Adsorption has been described in order to eliminate or lower concentration of a wide range of dissolved pollutants (organic or inorganic) in the effluent [4]. Dye removal by different sorbents was evaluated [5, 6]. Activated carbon is the most widely used adsorbent for this purpose. It has high capacity for adsorption of organic maters, but its uses are limited, because of its high cost [7, 8]. This has led to search for cheaper sorbents such as mineral clays [9–12], sawdust [13–16], and so on. Recently, various kinds of activated carbon have been achieved from different agriculture wastes and used as low-cost sorbents for removal of heavy metals, organic
Study on the Production of Activated Carbon from Straw Pulp and Paper Black Liquor

Yang Runchang,Zhou Shutian,

环境科学 , 1991,
Abstract: An experimental study on the production of activated carbon from straw pulp and paper black liquor by acid hydrolysis carbonization and ZnCl2 activation was curried out. Results show that about twenty grams of activated carbon can be obtained from a litre of 7-8 Be straw pulp and paper black liquor. The iodine number and methylene blue of the activated carbon thus produced are higher than 1000 mg/g and 180 ml/g, respectively. The main quality indices of the product are better than those of LY216-79 produced in China and JIS 1426 Grade 1 produced in Japan. After removal of the activated carbon, the CODcr in the liquor reduced by 72%, and the colority reduced by 93%. The residual liquor can be used for preparing Na2SO4 and furfural.
Adsorption of Reactive Dyes on Activated Carbon Developed from Enteromorpha prolifera  [PDF]
Deshuai Sun, Zhongyi Zhang, Mengling Wang, Yude Wu
American Journal of Analytical Chemistry (AJAC) , 2013, DOI: 10.4236/ajac.2013.47A003

Activated carbon was prepared from Enteromorpha prolifera by zinc chloride activation. The adsorption behaviors of three reactive dyes (Reactive Red 23, Reactive Blue 171 and Reactive Blue 4) onto this biomass activated carbon were investigated in batch systems. The experimental findings showed that the removal efficiencies of three dyes onto activated carbon were maximum at the initial solution pH of 4.5 - 6.0. Thermodynamic studies suggested that adsorption reaction was an endothermic and spontaneous process. Adsorption isotherm of the three dyes obeyed Freundlich isotherm modal. Dye adsorption capacities of activated carbon were 59.88, 71.94 and 131.93 mg·g?1 for RR23, RB171 and RB4 at 27?C, respectively. Second-order kinetic models fitted better to the equilibrium data of three dyes. The adsorption process on activated carbon was mainly controlled by intraparticle diffusion mechanism.

Adsorption of Organic Dyes from Aqueous Solution by Surfactant Modified Corn Straw  [PDF]
C. Umpuch,B. Jutarat
International Journal of Chemical Engineering and Applications , 2013, DOI: 10.7763/ijcea.2013.v4.279
Abstract: The modification of adsorbent with a cationic surfactant is an effective and inexpensive method to enhance sorption capability of adsorbent. In this study, raw corn straw, modified with a cationic surfactant, tetradecyltrimethyl ammonium bromide was used as adsorbent for dye removal from aqueous solution. The modification caused surface properties of the adsorbent altered from hydrophilic to hydrophobic. To comprehend the modification, the physical property of adsorbents was characterized by BET surface analysis, FTIR-spectra and SEM images. The adsorption of two organic dyes namely blue21 and yellow20 on the modified adsorbent has been investigated in three batch adsorption experiments. Firstly, kinetic study was performed. It was found that the equilibrium time was at 180 min and the kinetic data obeyed pseudo-second order kinetic model. Secondly, the effect of the pH solution was investigated. It was found that the adsorption capacity decreased at a low level with increase in the solution pH. Finally, the adsorption isotherms experiment was conducted and the equilibrium adsorption data was fitted into Langmuir and Freudlich isotherms and the system followed only the Freulich equation. From the above result, the corn straw modified by cationic surfactant is an effective adsorbent for removal of the organic dyes from aqueous solution.
Preparation and utilization of wheat straw anionic sorbent for the removal of nitrate from aqueous solution
WANG Yu,GAO Bao-yu,YUE Wen-wen,YUE Qin-yan,
,GAO Bao-yu,YUE Wen-wen,YUE Qin-yan

环境科学学报(英文版) , 2007,
Abstract: In order to reduce the impact of eutrophication caused by agricultural residues(i.e.,excess nitrate)in aqueous solution,economic and effective anionic sorbents are required.In this article,we prepared anionic sorbent using wheat straw.Its structural characteristics and adsorption properties for nitrate removal from aqueous solution were investigated.The results indicate that the yield of the prepared anionic sorbent,the total exchange capacity,and the maximum adsorption capacity were 350%,2.57 mEq/g,and 2.08 mmol/g, respectively.The Freundlich isotherm mode is more suitable than the Langmuir mode and the adsorption process accords with the first order reaction kinetic rate equation.When multiple anions(SO_4~(2-),H_2PO_4~-,NO_3~-,and NO_2~-)were present,the isotherm mode of prepared anionic sorbent for nitrate was consistent with Freundlich mode;however,the capacity of nitrate adsorption was reduced by 50%.In alkaline solutions,about 90% of adsorbed nitrate ions could be desorbed from prepared anionic sorbent.The results of this study confirmed that the wheat straw anionic sorbent can be used as an excellent nitrate sorbent that removes nitrate from aqueous solutions.
R. Gong,Y. Du,C. Li,S. Zhu
Iranian Journal of Environmental Health Science & Engineering , 2011,
Abstract: Thiol rice straw (TRS) was prepared by esterifying thioglycolic acid onto rice straw in the medium of acetic anhydride and acetic acid with sulfuric acid as catalyst. The sorption of lead (Pb) on TRS from aqueous solution was subsequently investigated. The batch experiments showed that Pb removal was dependent on initial pH, sorbent dose, Pb concentration, contact time, and temperature. The maximum value of Pb removal appeared at pH 5. For 100 mg/L of Pb solution, a removal ratio of greater than 98% could be achieved with 2.0 g/L or more of TRS. The isothermal data of Pb sorption conformed well to the Langmuir model, and the maximum sorption capacity (Qm) of TRS for Pb was 104.17 mg/g. The equilibrium of Pb removal was reached within 120 min. The Pb removal process could be described by the pseudo-first-order kinetic model. The thermodynamic study indicated that the Pb removal process was spontaneous and endothermic.
Kinetics and thermodynamics for Cu2+ adsorption by modified corn straw

Chen Yu,Gong Zhengjun,Yang Shunsheng,Sun Caiyun,

环境工程学报 , 2013,
Abstract: A sort of modified corn straw by using ZnCl2 as activating agent was used as adsorbent for removal of Cu2+ from aqueous solution. The influences of dosage, pH, adsorption time, initial concentration and reaction temperature were investigated on adsorption properties through dynamic tests. Adsorption isotherm models, thermodynamics models and kinetics models of the adsorption process between modified corn straw and Cu2+ were systematically studied. The results showed that the modified corn straw had maximum adsorption efficiencies when the dosage was 0.2 g, the pH was 6. The adsorption reached equilibrium after 8 hours. The adsorption process can be fitted very well by Langmuir and Freundlich adsorption isotherms and the quasi-second order kinetics equation. Gibbs free energy was less than zero, which showed that the reaction process was spontaneous.
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