Removal of basic dyes from aqueous solution by low-cost adsorbent: Wood apple shell (Feronia acidissima)

The adsorption of two basic dyes, methylene blue (MB) and crystal violet (CV) on wood apple shell (WAS) were investigated using a batch adsorption technique. A series of experiments were undertaken in an agitated batch adsorber to assess the effect of the system variables such as solution pH, dye concentration and temperature. Removal of dyes was observed to be most effective at higher pH. Freundlich and Langmuir isotherm models were applied to the equilibrium data. The results showed that Langmuir equation fits better than the Freundlich equation. It was observed that the WAS adsorbent showed higher adsorption capacity for crystal violet (130 mg/g) than methylene blue (95.2 mg/g). The FTIR studies indicate that the interaction of dye and WAS surface is via the nitrogen atoms of the adsorbate and oxygen groups of the adsorbent. The adsorption of dyes onto WAS proceeds according to a pseudo-second-order model. Thermodynamic parameters such as free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were also calculated. The studies show that WAS, a lignocellulosic inexpensive material, can be an alternative to other expensive adsorbents used for dye removal in wastewater treatment.     

Porous structure and adsorptive properties of pineapple peel based activated carbons prepared via microwave assisted KOH and K2CO3 activation

The present research explores the feasibility of microwave irradiation for preparation of high surface area activated carbon from pineapple peel (PPAC), an agricultural effluent emitted from the food can processing industries via KOH and K₂CO₃ activation. The activation process was performed at the microwave power of 600 W and irradiation time of 6 min. The equilibrium behavior of PPAC was investigated by performing batch adsorption experiments using methylene blue as adsorbate. Nonlinear adsorption isotherm models, Langmuir, Freundlich and Temkin were used to simulate the equilibrium data. KOH activated sample demonstrated a better development of pore structure, with the BET surface area, total pore volume and average pore size of 1006 m²/g, 0.59 m³/g and 23.44 Å, respectively, while the monolayer adsorption capacity of methylene blue was determined to be 462.10 mg/g. The findings support the potential use of microwave assisted KOH and K₂CO₃ activation as a promising activation technique.     

Equilibrium modeling for the adsorption of methylene blue from aqueous solutions on activated clay minerals

This work reports the application of an activated clay mineral as adsorbent for the removal of a basic dye, methylene blue (MB), from aqueous solutions. The thermal treatment at 300 °C for 2 h and the acid activation with nitric acid of 0.5 mol/dm³ under reflux conditions improve the adsorption capacity of the raw clay mineral. A maximum of 500 mg/g of MB at equilibrium is achieved. Equilibrium data are mathematically modelled using the Freundlich, Langmuir and Toth isotherm adsorption models.     

Macroporous chitosan/polyvinyl alcohol composite adsorbents based on activated carbon substrate

In current work, granular activated carbon (AC) was impregnated with different blends of chitosan (CS) and polyvinyl alcohol (PVA), (1:1, 1:2 and 2:1 w/w) polymers. Batch adsorption of methylene blue from water was studied using composite adsorbents. Isotherms and kinetics of adsorption on pristine, acidified and composite ACs were investigated and compared. FTIR, SEM, synthesis yield, swelling ratio and abrasion hardness analyses were selected for characterizing the adsorbents. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were employed to study the adsorption kinetics and, the pseudo-first-order model provided a better fit. Equilibrium results revealed that both Langmuir and Freundlich isotherms could well describe the adsorption equilibrium. Activated carbon/chitosan adsorbent suggested the highest adsorption capacity (468.7 mg/g) which was around 33 mg/g larger than that of the pristine activated carbon (435.2 mg/g). Moreover, AC/CS/PVA composites demonstrated the superior uptake rate and swelling degree in spite of having inferior yield of production. The hardness value was improved as a result of the polymer coating especially with the blends of CS and PVA due to developed interconnected network of the resultant coating layer. Generally, the results indicated that the role of CS was more highlighted in elevation of adsorption capacity while PVA was more effective in kinetic rate enhancement.     

Comparative study of methylene blue dye adsorption onto activated carbon,graphene oxide,and carbon nanotubes

Three different carbonaceous materials, activated carbon, graphene oxide, and multi-walled carbon nanotubes, were modified by nitric acid and used as adsorbents for the removal of methylene blue dye from aqueous solution. The adsorbents were characterized by N₂ adsorption/desorption isotherms, infrared spectroscopy, particle size, and zeta potential measurements. Batch adsorption experiments were carried out to study the effect of solution pH and contact time on dye adsorption properties. The kinetic studies showed that the adsorption data followed a pseudo second-order kinetic model. The isotherm analysis indicated that the adsorption data can be represented by Langmuir isotherm model. The remarkably strong adsorption capacity normalized by the BET surface area of graphene oxide and carbon nanotubes can be attributed to π–π electron donor acceptor interaction and electrostatic attraction.     

木焦油基活性碳的制备及其对亚甲基蓝的吸附性能研究

木焦油是木质生物质材料的高温裂解产物。以木焦油为碳源,以甲醛化处理后的木焦油为前体,通过碳化-活化制备木焦油基活性碳材料。并以制备的木焦油基活性碳为吸附剂,研究了其对模拟水体中亚甲基蓝的吸附性能。结果表明,以木焦油为前驱体经高温碳化活化制备的多孔活性碳,比表面积可达1373Sm_²?g_^-1,表面含有丰富的含氧官能团。木焦油基活性碳对亚甲基蓝具有良好的吸附性能,准二级动力学模型能更准确的描述木焦油基活性碳吸附亚甲基蓝的动力学过程。吸附等温线更符合Langmuir等温吸附模型,木焦油基活性碳对亚甲基蓝的最大吸附容量可达559 mg?g_^-1。热力学分析表明亚甲基蓝在木焦油基活性碳上的吸附是放热和自发的。利用木焦油制备的活性碳材料对亚甲基蓝具有较高的吸附容量,是一种具有潜在应用前景的吸附材料。     

微波辐照巴旦杏核壳制备活性炭及其吸附性能研究

以巴旦杏核壳为原料,采用微波辐照法制备活性炭。考察了活化条件对活性炭得率和吸附性能的影响。研究结果表明,在活化剂种类、活化剂用量、微波功率和辐照时间4个因素中,微波辐照时间对活性炭质量指标影响最大,延长时间可以提高其产品的得率和吸附性能。巴旦杏核壳基质活性炭的最佳制备工艺：巴旦杏核壳10g,固液比1：3（g：mL）,磷酸质量分数40％、浸溃24h,微波功率640W、活化时间16min。在此条件下制得的活性炭的亚甲基蓝吸附值为231．5mg/g,活性炭得率为56．8％。二级动力学模型能很好的描述巴旦杏核壳活性炭对亚甲基蓝大分子的吸附动力学过程。吸附符合Freundlich吸附等温线方程。     

Preparation of activated carbon derived from Jatropha curcas fruit shell by simple thermo-chemical activation and characterization of their physico-chemical properties

High surface area activated carbons were prepared by simple thermo-chemical activation of Jatropha curcas fruit shell with NaOH as a chemical activating agent. The effects of the preparation variables, which were impregnation ratio (NaOH:char), activation temperature and activation time, on the adsorption capacity of iodine and methylene blue solution were investigated. The activated carbon which had the highest iodine and methylene blue numbers was obtained by these conditions as follows: 4:1 (w/w) NaOH to char ratio, 800 °C activation temperature and 120 min activation time. Characterization of the activated carbon obtained was performed by using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and nitrogen adsorption isotherm as BET. The results present that the activated carbon possesses a large apparent surface area (S_BET = 1873 m²/g) and high total pore volume (1.312 cm³/g) with average pore size diameter of 28.0 Å.     

Coniferous Wood Sawdust-based Activated Carbons as Adsorbents Obtained with the Use of Microwave Radiation

Activated carbons were prepared by physical and direct activation of sawdust pellets coming from coniferous trees, with the use of microwave radiation. The activated carbons obtained were used as adsorbents for the removal of methylene blue (MB) from aqueous solutions. Liquid-phase adsorption experiments were conducted and the maximum adsorption capacity of each activated carbon sample was determined. The effects of activation procedure as well as adsorption tests parameters i.e., temperature, pH, initial methylene blue concentration, and contact time on the sorption capacity of each activated carbon were investigated. The kinetic models for MB adsorption on the activated carbons were also studied. Better fit to the experimental data was obtained with the Langmuir isotherm than Freundlich one, for all samples.     

污泥活性炭的制备及其脱色性能

以污水污泥为原料,采用物理活化法制得污泥活性炭,并用该活性炭处理染料废水,研究了pH值、污泥活性炭的投加量、温度、吸附时间等因素对染料废水的脱色率和COD去除率的影响。结果表明:用污泥制备的活性炭,其碘值和亚甲基兰吸附值分别为254.36 mg/g和20.26 mg/g,而且BET比表面积值为25.1995 m2/g,总孔容积为0.0399 m3/g,具有较好的吸附性能;将污泥活性炭用来吸附氨基黑染料,并与商品活性炭处理氨基黑染料的效果进行对比,自制污泥活性炭的脱色效果达到了商品活性炭的水平;污泥活性炭对氨基黑染料的吸附过程符合Langmuir吸附等温线。     

蒲草叶基活性炭的制备及性能研究

以蒲草叶（CL）为原料、CO₂为活化剂,采用两步法制备蒲草叶基活性炭（CL-AC）。利用SEM和BET对CL-AC的结构和形貌进行表征。结果表明CL-AC具有发达的孔隙结构。活化温度800℃、活化时间20 min条件下制得的活性炭样品（CL-AC3）的比表面积最高,达到570.03 m²/g。5 000次循环后,CL-AC3的电容保持率为90.56%。当电流密度为0.5 A/g时,比电容达到111 F/g。采用单因素试验对CL-AC3吸附亚甲基蓝的条件进行优化,结果表明,较优吸附条件为吸附剂投加量12.5 mg、溶液初始质量浓度50 mg/L、温度303.15 K、吸附时间300 min,该条件下吸附量达到199.22 mg/g。亚甲基蓝在CAC上的吸附过程遵循准二级动力学模型和Langmuir等温线,吸附过程是自发吸热。     

废弃粉末活性炭热解再生实验及表征分析

通过对废弃粉末活性炭（WPAC）进行热解再生实验,采用热重（TG）、红外分析（FTIR）、表面分析（BET）、X射线衍射（XRD）表征手段,分析了废弃粉末活性炭热解再生前后的比表面积、孔隙结构及再生过程中有机物分解的初步规律。同时比较了废弃粉末活性炭再生前后对亚甲基蓝（MB）的吸附性能,对WPAC热解再生效果进行了评价。实验得出的最佳热解再生条件是以氮气为载气,热解温度650℃,热解时间2h。在此再生条件下,再生炭（RPAC）的比表面积为1161.4m²/g,恢复到新鲜活性炭的94.5%;废弃粉末活性炭再生前后对亚甲基蓝的吸附等温线符合Langmuir模型,吸附容量为420.5mg/g,恢复到新鲜炭的89.6%。由此结果表明,WPAC经热解再生后表面化学性质、孔隙结构及吸附性能均得到有效恢复。     

Hexavalent chromium adsorption on superparamagnetic multi-wall carbon nanotubes and activated carbon composites

Hexavalent chromium (Cr(VI)) adsorption from aqueous solutions on magnetically modified multi-wall carbon nanotubes (M-MWCNT) and activated carbon (M-AC) was investigated. M-MWCNT and M-AC were prepared by co-precipitation method with Fe²⁺:Fe³⁺ salts as precursors. The magnetic adsorbents were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). The effects of amount of adsorbents, contact time, initial pH, temperature and the initial concentration of Cr(VI) solution were determined. The adsorption equilibrium, kinetics, thermodynamics and desorption of Cr(VI) were investigated. Equilibrium data fitted well with the Langmuir isotherm for both of the adsorbents. The theoretical adsorption capacities are 14.28 mg/g of M-MWCNT and 2.84 mg/g of M-AC. Cr(VI) adsorption kinetics was modeled with pseudo-second order model, intra-particle diffusion model and Bangham model. Thermodynamic parameters were calculated and ΔG°, ΔH° and ΔS° indicate that the adsorption of Cr(VI) onto M-MWCNT and M-AC was exothermic and spontaneous in nature. Results revealed that M-MWCNT is an easily separated effective adsorbent for Cr(VI) adsorption from aqueous solution.     

山竹壳活性炭吸附亚甲基蓝性能研究

以山竹壳为原料,采用磷酸—硫酸活化法制备了比表面积为1730m~2·g~(-1)的活性炭。研究了山竹壳活性炭吸附亚甲基蓝的吸附性能,考察了亚甲基蓝溶液的pH、不同初始浓度、吸附时间、温度等条件对吸附效果的影响。应用准一级动力学方程、准二级动力学方程模拟了山竹壳活性炭吸附亚甲基蓝的动力学过程,结果表明准二级动力学方程适合描述整个吸附过程。用Langmuir和Freundlich模型模拟吸附等温线,Langmuir方程更适合描述此吸附过程,在298K下最大单层吸附量为526.31mg·g~(-1)。计算了吉布斯自由能(ΔG~0)、焓变(ΔH~0)、熵变(ΔS~0)等热力学参数,ΔG~0、ΔH~0、ΔS~0均小于0,说明此吸附过程是一个自发进行的、放热的、趋于有序的吸附过程。     

Physical and chemical characteristics of polymer-based spherical activated carbon and its ability to adsorb organics

The characterization of a polymeric spherical activated carbon (PAC) was performed by comparing its adsorption, porosity, functional groups and some of the physical properties with a commercial spherical activated carbon (CAC). The PAC was about 4 times superior to the CAC with respect to the mechanical strength. The micropore volume of the PAC was about 5% smaller than that of the CAC. The maximum methylene blue adsorption values of the PAC and the CAC were 32 and 14 mg g⁻¹, respectively, which indicated low mesopore volumes as consistent with the values of BJH volume. This resulted in the low butane working capacity values for both activated carbons. Adsorption parameters for the Langmuir and the Freundlich isotherm models were determined for all organic substances tested. Both isotherms were suitable models to analyze the equilibrium data for the removal of all organics. However, the Langmuir model fitted better than the Freundlich model and the adsorption capacities of the PAC were somewhat higher than those of the CAC. The chemical properties of the activated carbons, the pH of solutions and the substituents on absorbates have an effect on adsorption of the organics tested.     

The study of the potential capability of sugar beet pulp on the removal efficiency of two cationic dyes

This study utilizes sugar beet pulp as a low-cost absorbent to remove two different cationic dyes, methylene blue and safranin, in aqueous solutions. The effects of operational parameters on the efficiency of dye removal including pH, adsorbent mass, initial dye concentration and contact time have been investigated. All sets of experiments were carried out in batch mode. For both dyes, the maximum absorption was reached at pH 10 while point zero charge was known to be at pH 6. Boehm method showed that the amount of the acidic and basic groups have been 0.4075 mmol g⁻¹ and 0.0089 mmol g⁻¹, respectively. Freundlich and Langmuir models were used to analyse the obtained experimental data. In comparison, Langmuir model was understood to be a better fit for the experimental data than Freundlich model. Pseudo first-order and pseudo second-order models were used to determine the adsorption kinetics and it was observed that pseudo second-order model was the most suited model for both dyes. The equilibrium state for both dyes was reached after 210 min of the absorption experiment with more than 93% removal of dyes. The absorption capacities were found to be 211 mg/g and 147 mg/g for methylene blue and safranin, respectively.     

基于响应面模型对花生壳基活性炭工艺的优化

为优化木质活性炭制备的工艺条件,以农林废弃物花生壳为原料,磷酸为主活化剂,硫酸为辅助活化剂,利用响应面模型分析磷酸质量分数、浸渍比(活化剂体积与花生壳质量比)、活化时间、活化温度对活性炭性能的影响。结果表明：通过Box-Behnken试验建立的二次多项式数学模型的P值都小于0.000 1,校正决定系数(R²)分别为0.990 2和0.997 8,变异系数(CV) < 10%,试验的可信度和精确度高,回归方程成立。通过二次回归模型得到磷酸-硫酸活化法制备花生壳基活性炭的最佳工艺条件为花生壳粉末1 g,磷酸质量分数57.7%,浸渍比2:1,活化时间117 min,活化温度550 ℃。在最佳工艺条件下,制备的活性炭亚甲基蓝吸附值为147.2 mg/g,碘吸附值1 022.03 mg/g,实际值与预测值接近,重复性好。利用磷酸-硫酸活化法制备的花生壳基活性炭的内部中小孔较发达,具有较强的吸附能力和脱附能力。     

Adsorptive removal of methylene blue from aqueous solution on activated carbon prepared from Malawian baobab fruit shell wastes: Equilibrium,kinetics and thermodynamic studies

Baobab fruit shell (BFS), a renewable bio-waste from Malawian baobab tree was used as a precursor for the production of a low-cost activated carbon to remove methylene blue (MB) from aqueous solution. Parameters such as contact time, initial methylene blue concentration, adsorbent dose and temperature were studied. The adsorption process can be well described by both Langmuir isotherm and the pseudo-second-order kinetics. The maximum monolayer adsorption capacity of MB dye was ca. 334.45 mg/g. The negative value of the Gibb’s free energy and positive value of adsorption enthalpy showed the spontaneous nature and endothermic nature of the adsorption process, respectively.     

The Properties of Activated Carbon Made from Waste Newsprint Paper

Activated carbon is a porous material made by activation of carbon materials, such as coal, by steam or carbon dioxide gas to form numerous micropores on the surface which gives the material high adsorption characteristics and it is widely used as a purifier for water and air. In this research, to develop a new use for waste paper, activated carbon was prepared from waste newsprint paper and its adsorption characteristics were measured. As a result, activated carbon with an iodine adsorption capacity of 1310 mg/g, a methylene blue adsorption capacity of 326 mg/g and a specific surface area of 1000 m2/g was obtained. These adsorption capacities were almost the same as ordinary activated carbon on the market.     

Adsorption of Cd(II), Hg(II) and Zn(II) from aqueous solution using mesoporous activated carbon produced from Bambusa vulgaris striata

Mesoporous activated carbon (surface area of 608 m²/g) has achieved high efficiency in removal of cadmium, mercury and zinc ions from water solution. The proposed low-cost adsorbent was physically activated with water steam from the bamboo species Bambusa vulgaris striata. The batch studies suggested an activated carbon dose of 0.6 g/L, solution pH of 9 and an equilibrium time of 16 h in static conditions. The pseudo-second order equations represented the adsorption kinetics with high correlation. Fitting of the experimental results to the Langmuir, Freundlich, Redlich–Peterson and Toth isotherm models showed an almost homogeneous surface coverage and presence of physical adsorption. The highest adsorption capacities, calculated from the Langmuir model, are 239.45, 248.05 and 254.39 mg/g of cadmium, mercury and zinc, respectively.