A comparative adsorption/biosorption study of mono-chlorinated phenols onto various sorbents

The potential use of dried activated sludge and fly ash as a substitute for granular activated carbon for removing mono-chlorinated phenols (o-chlorophenol and p-chlorophenol) was examined. The pollutant binding capacity of the adsorbent/biosorbent was shown to be a function of substituted group, initial pH and initial mono-chlorinated phenol concentration. The working sorption pH value was determined as 1.0 and the equilibrium uptake increased with increasing initial mono-chlorinated phenol concentration up to 500 mg dm(-3) for all the mono-chlorinated phenol-sorbent systems. The suitability of the Freundlich, Langmuir and Redlich-Peterson adsorption models to the equilibrium data were investigated for each mono-chlorinated phenol-sorbent system. The results showed that the equilibrium data for all the mono-chlorinated phenol-sorbent systems fitted the Redlich-Peterson model best within the concentration range studied.     

Activated carbon from Ceiba pentandra hulls, an agricultural waste, as an adsorbent in the removal of lead and zinc from aqueous solutions

The ability of low-cost activated carbon prepared from Ceiba pentandra hulls, an agricultural waste material, for the removal of lead and zinc from aqueous solutions has been investigated. In the batch tests experimental parameters were studied, including solution pH, contact time, adsorbent dose and initial metal ions concentration. The adsorbent exhibited good sorption potential at pH 6.0. Maximum removal of lead (99.5%) and of zinc (99.1%) with 10 g/l of sorbent was observed at 50 mg/L sorbate concentration. Removals of about 60-70% occurred in 10 min, and equilibrium was attained at around 50 min for both metals. The functional groups (CO, SO,-OH) present on the carbon surface were responsible for the adsorption of metal ions. The adsorption parameters were analysed using both the Freundlich and Langmuir models. The data are better fitted by the Freundlich isotherm as compared to Langmuir model, and the adsorption capacities for lead and zinc were 25.5 and 24.1 mg/g, respectively. Kinetics of adsorption obeyed a second order rate equation and the rate constant was found to be 2.71 x 10(-2) and 2.08 x 10(-2) g/mg/min for lead and zinc, respectively. The desorption studies were carried out using dilute HCl, and the effect of HCl concentration on desorption was studied. Maximum desorptions of 85% for lead and 78% for zinc were attained with 0.15 M HCl.     

核桃壳吸附剂对水中Pb2+的吸附

采用自制核桃壳吸附剂,利用静态吸附法,处理模拟含Pb²⁺废水。实验结果表明：当初始Pb²⁺的质量浓度20.00 mg/L、初始废水pH=5.5、吸附剂加入量12 g/L、吸附剂粒径1.60~2.50 mm、吸附时间120 min时,核桃壳吸附剂对Pb²⁺的去除率为91.7%;吸附剂对Pb²⁺的吸附行为满足拟二级吸附动力学方程,吸附等温线满足Langmuir等温方程,饱和吸附量达到3.903 mg/g;吸附饱和的吸附剂可用浓度 0.1 mol/L的硝酸解吸,经解吸后的吸附剂可重复利用3次。     

Orange peel as an adsorbent in the removal of acid violet 17 (acid dye) from aqueous solutions

The effectiveness of orange peel in adsorbing Acid violet 17 from aqueous solutions has been studied as a function of agitation time, adsorbent dosage, initial dye concentration and pH. The adsorption follows both Langmuir and Freundlich isotherms. The adsorption capacity Q0 was 19.88 mg/g at initial pH 6.3. The equilibrium time was found to be 80 min for 10, 20, 30 and 40 mg/L, dye concentration respectively. A maximum removal of 87% was obtained at pH 2.0 for an adsorbent dose of 600 mg/50 ml of 10 mg/L dye concentration. Adsorption increases with increase in pH. Maximum desorption of 60% was achieved in water medium at pH 10.0.     

Experimental and Modeling Studies for the Removal of Crystal Violet Dye from Aqueous Solutions using Eco-friendly <Emphasis Type="Italic">Gracilaria corticata</Emphasis> Seaweed Activated Carbon/Zn/Alginate Polymeric Composite Beads

This research article describes, an eco-friendly activated carbon prepared from the Gracilaria corticata seaweeds which was employed for the preparation of biodegradable polymeric beads for the efficient removal of crystal violet dye in an aqueous solution. The presence of chemical functional groups in the adsorbent material was detected using FTIR spectroscopy. The morphology and physical phases of the adsorbent materials were analyzed using SEM and XRD studies respectively. Batch mode dye adsorption behavior of the activated carbon/Zn/alginate polymeric beads was investigated as a function of dosage, solution pH, contact time, initial dye concentration and temperature. Maximum dye removal was observed at a pH of 5.0, 1 g of adsorbent dosage with 60 mg/L dye concentration, 50 min of contact time and at 30 °C. The equilibrium modeling studies were analyzed with Freundlich and Langmuir adsorption isotherms and the adsorption dynamics was predicted with Lagergren’s pseudo-first order, pseudo-second order equations and intra particle diffusion models. The process of dye removal followed a pseudo second-order kinetics rather than pseudo first order. The thermodynamic parameters like standard Gibbs free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) were determined and the results imply that the adsorption process was spontaneous, endothermic and increases the randomness between the adsorbent and adsorbate. The results from the experimental and correlation data reveal that the Gracilaria corticata activated carbon/Zn/alginate polymeric beads have proved to be an excellent adsorbent material for the removal of CV dye.     

生物炭对铅离子的吸附性能

以废弃松木屑为原料,采用控制热分解法制备了生物炭。运用BET和FTIR等技术对生物炭进行了表征,考察了生物炭对铅离子的吸附效果,并探讨了吸附机理。表征结果显示,700℃氨气处理的生物炭,其比表面积和总孔体积显著增大。实验结果表明:生物炭对铅离子的吸附效果优于普通活性炭,且以700℃氨气处理的生物炭为最佳;随溶液pH的升高生物炭对铅离子的去除率增大,当pH为4~6时去除效果较好;在溶液pH为6、初始铅离子质量浓度为50 mg/L、吸附剂加入量为1 g/L、吸附时间为6 h的条件下,700℃氨气处理的生物炭对铅离子的去除率达99%以上;700℃氨气处理的生物炭的Langmuir吸附常数和Freundlich吸附常数远大于普通活性炭和其他工艺的生物炭;铅离子在生物炭上的吸附过程符合拟二级动力学方程。     

Uptake of dyes by a promising locally available agricultural solid waste: coir pith

The adsorption of rhodamine-B and acid violet by coir pith carbon was carried out by varying the parameters such as agitation time, dye concentration, adsorbent dose and pH. The adsorption followed both Langmuir and Freundlich isotherms. The adsorption capacity was found to be 2.56 mg and 8.06 mg dye per g of the adsorbent for rhodamine-B and acid violet, respectively. Adsorption of dyes followed first order rate kinetics. Acidic pH was favorable for the adsorption of acid violet and alkaline pH was favorable to rhodamine-B. Desorption studies showed that alkaline pH was favorable for the desorption of acid violet and acidic pH was favorable for the desorption of rhodamine-B.     

Adsorption of malachite green on groundnut shell waste based powdered activated carbon

In the present technologically fast changing situation related to waste management practices, it is desirable that disposal of plant waste should be done in a scientific manner by keeping in view economic and pollution considerations. This is only possible when the plant waste has the potential to be used as raw material for some useful product. In the present study, groundnut shell, an agricultural waste, was used for the preparation of an adsorbent by chemical activation using ZnCl2 under optimized conditions and its comparative characterisation was conducted with commercially available powdered activated carbon (CPAC) for its physical, chemical and adsorption properties. The groundnut shell based powdered activated carbon (GSPAC) has a higher surface area, iodine and methylene blue number compared to CPAC. Both of the carbons were used for the removal of malachite green dye from aqueous solution and the effect of various operating variables, viz. adsorbent dose (0.1-1 g l(-1)), contact time (5-120 min) and adsorbate concentrations (100-200 mg l(-1)) on the removal of dye, has been studied. The experimental results indicate that at a dose of 0.5 g l(-1) and initial concentration of 100 mg l(-1), GSPAC showed 94.5% removal of the dye in 30 min equilibrium time, while CPAC removed 96% of the dye in 15 min. The experimental isotherm data were analyzed using the linearized forms of Freundlich, Langmuir and BET equations to determine maximum adsorptive capacities. The equilibrium data fit well to the Freundlich isotherm, although the BET isotherm also showed higher correlation for both of the carbons. The results of comparative adsorption capacity of both carbons indicate that groundnut shell can be used as a low-cost alternative to commercial powdered activated carbon in aqueous solution for dye removal.     

Removal of Cr6 + and Ni2+ from aqueous solution using bagasse and fly ash

Raw bagasse and fly ash, the waste generated in sugar mills and boilers respectively have been used as low-cost potential adsorbents. Raw bagasse was pretreated with 0.1N NaOH followed by 0.1N CH3COOH before its application. These low-cost adsorbents were used for the removal of chromium and nickel from an aqueous solution. The kinetics of adsorption and extent of adsorption at equilibrium are dependent on the physical and chemical characteristics of the adsorbent, adsorbate and experimental system. The effect of hydrogen ion concentration, contact time, sorbent dose, initial concentrations of adsorbate and adsorbent and particle size on the uptake of chromium and nickel were studied in batch experiments. The Sorption data has been correlated with Langmuir, Freundlich and Bhattacharya and Venkobachar adsorption models. The efficiencies of adsorbent materials for the removal of Cr(VI) and Ni(II) were found to be between 56.2 and 96.2% and 83.6 and 100%, respectively. These results were obtained at the optimized conditions of pH, contact time, sorbent dose, sorbate concentration of 100 mg/l and with the variation of adsorbent particles size between 0.075 and 4.75 mm. The order of selectivity is powdered activated carbon > bagasse > fly ash for Cr(VI) removal and powdered activated carbon > fly ash > bagasse for Ni(II) removal.     

含油浮渣制备含碳吸附剂并用于含油污水的处理

以含油浮渣为原料制备含碳吸附剂,并用于含油污水的处理。用比表面分析仪和SEM技术对吸附剂进行表征。通过正交实验和单因素实验考察吸附剂加入量、吸附时间及温度、污水pH对污水处理效果的影响。表征结果显示,含碳吸附剂碳元素含量高达90%(w)以上,表面粗糙,孔径分布以中孔为主,比表面积477.5 m2/g,碘吸附值376.48 mg/g。实验结果表明:在吸附温度30℃及时间60 min、含碳吸附剂加入量20 g/L、污水pH为7的最佳实验条件下,处理初始COD为502.12 mg/L、石油类质量浓度45.31 mg/L.的含油污水,COD和石油类的去除率分别为91.51%和87.1%,处理后的COD和石油类质量浓度分别为42.62 mg/L和5.83 mg/1,达到GB 8978—1996《污水综合排放标准》中的二级排放标准;含碳吸附剂的污水处理效果优于术质活性炭。     

硝酸改性活性炭的制备及其对Cr（Ⅵ）

利用硝酸对颗粒活性炭进行改性,处理含铬废水,并考察了吸附时间、溶液pH、吸附剂加入量对改性活性炭吸附Cr（Ⅵ）效果的影响。实验结果表明：经过硝酸氧化改性的活性炭比表面积有所增加,官能团总量增加明显;吸附剂对Cr（Ⅵ）的去除率随振荡时间的增加而增加;对于质量浓度为10mg/L的100mLCr（Ⅵ）溶液,当溶液pH为中性,30%（体积分数）硝酸改性的颗粒活性炭的加入量为0.4g,其对Cr（Ⅵ）的最大去除率为98%。     

Physical and chemical properties study of the activated carbon made from sewage sludge

Preparation of activated carbon from sewage sludge is a promising way to produce a useful adsorbent for pollutants removal as well as to dispose of sewage sludge. The objective of this study was to investigate the physical and chemical properties of the activated carbon made from sewage sludge so as to give a basic understanding of its structure. The activated carbon was prepared by activating anaerobically digested sewage sludge with 5 M ZnCl2 and thereafter pyrolyzing it at 500 degrees C for 2 h under nitrogen atmosphere. The properties investigated in the present study included its surface area and pore size distribution, its elemental composition and ash content, its surface chemistry structure and its surface physical morphology. Furthermore, its adsorption capacities for aqueous phenol and carbontetrachloride were examined. The results indicated that the activated carbon made from sewage sludge had remarkable micropore and mesopore surface areas and notable adsorption capacities for phenol and carbon-tetrachloride. In comparison with commercial activated carbons, it displayed distinctive physical and chemical properties.     

水力空化-O3氧化联合超声吸附处理煤气化废水

采用水力空化-O₃氧化与超声吸附法联合处理煤气化废水。吸附剂以钙基膨润土为原料,经十六烷基三甲基溴化铵改性制得。通过单因素实验分别探讨了水力空化-O₃氧化与超声吸附的适宜处理条件,并在该条件下对废水进行联合处理。实验结果表明：在O₃通量194.4 mg/L、空化时间60 min、入口压力0.4 MPa、废水pH 10.00的优化条件下,水力空化-O₃氧化对COD和苯酚的去除率分别达67.3%和57.5%;在此基础上进一步采用超声吸附法处理废水,在吸附剂投加量0.06 g/mL、超声时间60 min、废水pH 4.00、吸附温度25 ℃的优化条件下,处理后出水中COD和苯酚质量浓度分别降至317.1 mg/L和117.9 mg/L;COD和苯酚的总去除率分别达97.9%和96.6%。     

Removal of fluoride from water using aluminum-modified activated carbon prepared from khat (Catha edulis) stems

This study investigated the fluoride removal efficiency and adsorption of a low-cost adsorbent prepared using aluminum-modified activated carbon from khat (Catha edulis) in a batch-mode reactor. The operating factors, including pH, adsorbent dose, and fluoride initial concentration, were optimized using the Box Behnken design of response surface methodology. The correlation coefficient (R²) for the removal of fluoride was found to be 0.93, showing the validity of the developed quadratic model. The results showed that, under optimized conditions of an adsorbent dose of 2.47 g/L, an initial fluoride concentration of 2.1 mg/L, an initial pH 6.08, and 60 min, 90% fluoride reduction was achieved. Meanwhile, the adsorption isotherm and kinetics followed the Langmuir adsorption model and the Pseudo second model, respectively, with a monolayer adsorption capacity of 0.3065 mg/g. On the other hand, Fourier transform infrared spectroscopy and scanning electron microscopy analyses revealed the formation of major peaks of components such as hydroxyl and carboxylic acids. The same optimum treatment conditions (adsorbent dose of 2.47 g/L, initial pH 6.08, and treatment time of 60 min) managed to remove low initial fluoride concentrations of 3.67 and 4.33 mg/L from real groundwater by 72.84% and 70.37%, respectively. The modified adsorbent prepared in this study successfully treat the low fluoride concentration to a level recommended by WHO for drinking water.     

Adsorptive Removal of Diuron Herbicide on Carbon Nanotubes Synthesized from Plastic Waste

In this study, carbon nanotubes (CNTs) were synthesized from waste polyethylene bottles and their use as an adsorbent for the removal of diuron herbicide from aqueous solution was evaluated. Batch adsorption was performed by varying adsorbent dosage, initial concentration, contact time, and temperature. Kinetic models applied to experimental data indicated that the pseudo-second-order model had the best fit. The equilibrium data were analyzed using different isotherm models. The adsorption capacity of CNTs for diuron removal, determined using the Hill isotherm, was approximately 40.37 mg/g at 303 K. From thermodynamic studies, the values of ΔH° (kJ/mol) and ΔS° [kJ/(mol K)] were calculated as ?17.307 and ?0.0528, respectively, which suggested that the adsorption process was exothermic. The negative values of ΔG° at three different temperatures indicated that adsorption of diuron on CNTs was favorable.     

碳纳米管-海藻酸钠复合吸附材料的制备及其对高浓度Cr（Ⅲ）的吸附

以碳纳米管（CNTs）和海藻酸钠（SA）为主要原料,制备了环境友好型的复合吸附材料——CNTs-SA。采用TEM和FTIR技术对吸附材料进行了表征,并采用静态法考察了溶液pH、吸附时间、原料固液比（m（CNTs）∶V（SA））等因素对CNTs-SA吸附Cr（Ⅲ）的影响。表征结果显示,CNTs-SA表面引入了更多的—COOH和—CO基团,导致其吸附Cr（Ⅲ）的效果较CNTs有了显著的提高。实验结果表明：在室温、初始Cr（Ⅲ）质量浓度4 000 mg/L、CNTs-SA加入量21 mg/mL、溶液pH 5、吸附时间3 h、m（CNTs）∶V（SA）=1.0 mg/mL的条件下,CNTs-SA对Cr（Ⅲ）的吸附量为120 mg/g,Cr（Ⅲ）去除率为61.5%;Freundlich等温吸附方程适合描述CNTs-SA对Cr（Ⅲ）的吸附行为。     

DTC类改性糯米淀粉的制备及其吸附水中Pb2+性能

采用碱法从天然糯米中提取糯米淀粉（SS）,经环氧氯丙烷交联、醚化,邻苯二胺胺化,CS₂亲核加成,最终制备出一种新型Pb²⁺吸附剂——二硫代氨基甲酸盐（DTC）类改性糯米淀粉（DTCS）。在吸附剂加入量2.0 g/L、Pb²⁺质量浓度30 mg/L的条件下,不同阶段改性产物吸附Pb²⁺的最佳pH均为7.0,吸附平衡时间为30 min。SS对Pb²⁺的吸附去除率仅为9.1%,经改性后吸附能力逐步提高,最终产物DTCS对Pb²⁺的吸附效果最佳,Pb²⁺去除率高达99.9%,平衡吸附量为14.97 mg/g。DTCS对Pb²⁺的吸附过程符合准二级吸附动力学模型,以化学吸附为主。     

花生壳活性炭吸附溶液中的铀

以农林废弃物花生壳为原料、氢氧化钾为活化剂、微波为热源,制备了花生壳活性炭。以花生壳活性炭为吸附剂吸附溶液中的U(VI),考察了初始U(VI)质量浓度、活性炭加入量、溶液pH、吸附时间对U(VI)去除效果的影响。实验结果表明,在溶液中初始U(VI)质量浓度为30mg/L、活性炭加入量为0.5g/L、溶液pH为5.5、吸附时间为150min的较佳条件下,活性炭对U(VI)的吸附量为56.37mg/g,U(VI)去除率为93.94％。     

Recycling of ‘waste’ FE(III)/CR(III) hydroxide for the removal of nickel from wastewater: Adsorption and equilibrium studies

Effects of Ni(II) concentration, agitation time, temperature and pH on adsorption of Ni(II) on Fe(III)/Cr(III) hydroxide, a waste by-product from fertilizer industry, have been investigated. The percent adsorption increased from 55 to 69% with increase in temperature from 20 to 40°C and from 32 to 77% with increase in pH from 3.7 to 7.5 and from 38 to 79% with decrease in Ni(II) concentration from 100 to 25 mg/L. The equilibrium data fit well with the Langmuir isotherm and the adsorption capacity was found to be 21.0 mg/g at 30°C. Thermodynamic parameters such as free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) were evaluated. The adsorption rate constant was higher at lower concentration of Ni(II) and at higher temperature. Desorption studies show that 70% of Ni(II) can be desorbed from the adsorbent at pH 4.0. The adsorbent was tested using nickel plating industry wastewater and the maximum percent removal was 97.     

Fluoride sorption by treated fly ash: kinetic and isotherm studies

High fluoride levels in drinking water have become a critical health hazard. In the present study, the performance of magnesia-loaded fly ash adsorption in the removal of fluoride from aqueous solution was investigated in a batch study. The effect of contact time, dosage, pH, temperature and agitation speed was studied at different values. The maximum removal efficiency was 88 % at 150 min. The effective dose of adsorbent was found to be 2.5 g/l. The optimum pH was found to be at pH 4. Kinetic studies and isotherm studies were also performed to understand the ability of the adsorbents. The monolayer adsorption capacity determined from the Langmuir adsorption equation was found to be 11.61 mg/g. The kinetic measurements suggested the involvement of pseudo-second-order kinetics in adsorption and were controlled by a particle diffusion process. Overall, the results of this study suggest that magnesia-loaded fly ash is an environmentally friendly, efficient and low-cost adsorbent, useful for the removal of fluoride from aqueous solution.