Activated Carbon from Rice Husk with One-Step KOH Mechanical Mixing Activation as Adsorbent for Treating Phenolic Wastewater

This study investigates how large-surface-area biocarbons with high phenolic adsorption capacities can be obtained from cheap and abundant rice husk(RH).The RH is directly mixed with potassium hydroxide(KOH)and activated in a flowing N_(2) atmosphere,and the effects of the pyrolysis temperature and KOH to RH ratio on the structure of the obtained activated carbon adsorbents and their adsorption of p-nitrophenol and phenol are studied.The results show that the optimum pyrolysis temperature of RH is 750℃,whereby the highest surface area of 2047 m^(2)/g and best adsorption performance are obtained with a KOH to RH ratio of 3:1.Moreover,the obtained biocarbons achieve a maximum adsorption capacity of 175 mg/g for phenol and 430 mg/g for p-nitrophenol,which are higher than most previously reported data.

Rice Husk at a Glance:From Agro-Industrial to Modern Applications

Excessive waste production has led to the concept of a circular bioeconomy to deliver valuable by-products and improve environmental sustainability.The annual worldwide rice production accounts for more than 750 million tons of grain and 150 million tons of husk.Rice husk(RH)contains valuable biomaterials with extensive applications in various fields.The proportions of each component depend primarily on rice genotype,soil chemistry,and climatic conditions.RH and its derivatives,including ash,biochar,hydrochar,and activated carbon have been placed foreground of applications in agriculture and other industries.While the investigation on RH’s compositions,microstructures,and by-products has been done copiously,owing to its unique features,it is still an open-ended area with enormous scope for innovation,research,and technology.Here,we reviewed the latest applications of RH and its derivatives,including fuel and other energy resources,construction materials,pharmacy,medicine,and nanobiotechnology to keep this versatile biomaterial in the spotlight.

Preparation and activity research of ecological nano mineral admixture from rice husk charcoal

The rice husk ash （ RHA） and silica （ Si02） nanoparticles are prepared from rice husk charcoal （RHC） by the methods of ventilated calcining and chemical precipitation, respectively, to remove the residual carbon which is harmful to cement composites. The structures and morphologies of these products are investigated by the Fourier transform infrared spectroscopy, X-ray diffraction, scanning/ transmission electron microscopy and N2 adsorption- desorption analyzer. The results show that the as-produced RHA and Si02 nanoparticles exist in amorphous phase without residual carbon, and exhibit porous structures with specific surface areas of 170.19 and 248. 67 m2 /g , respectively. The micro particles of RHA are aggregated by numerous loosely packed Si02 gel particles with the diameter of 50 to 100 nm. The Si02 nanoparticles are well dispersed with the average size of about 30 nm. Both the RHA and Si02 nanoparticles can significantly reduce the conductivity of saturated Ca（OH）2 solution and increase the early strength of the cement composites. They also exhibit high pozzolanic activity, indicating that they can be used as ecological nano mineral admixtures.

Removal of Cr(VI)from aqueous solution by Rice-husk-based activated carbon prepared by Dual-mode heating method

Rice husk-based activated carbon was prepared with the help of zinc chloride using microwave and electrical dual-mode heating.The pore characteristics and chemical properties of rice husk-based activated carbon(RH-AC)were characterized by BET,XRD,Raman spectra,FTIR and pHIEP(pH of isoelectric point).The specific surface area of RH-AC is 1719.32 m^(2)/g with a total pore volume of 1.05 cm^(3)/g.The performance of RH-AC for removing Cr(VI)from aqueous solution was examined considering the variation of the contact time(0-120 min),pH value(2.0-9.0),adsorbent dose(0.5-3.0 g/L),initial concentration(28-145 mg/L)and solvent temperature(15-45℃).The ideal pH for Cr(VI)removal is between 2.0 and 3.0 with the equilibrium time of 90 min,achieving the maximum adsorption capacity of 56.82 mg/g with the pH of 3.0.Comparable study on the established kinetic models and isotherms to simulate the removal of Cr(VI)by RH-AC was carried out to sort out the inherent mechanism of the absorption.Reasonable agreements could be obtained by the pseudo-second-order kinetic model and Langmuir,Freundlich and Tempkin isothermal models.Results from Body model simulation suggest that external mass transfer was the essential cause for rate-controlling in the adsorption process of Cr(VI).

Single and Binary Dye Adsorption of Methylene Blue and Methyl Orange in Alcohol Aqueous Solution via Rice Husk Based Activated Carbon:Kinetics and Equilibrium Studies

The present work was mainly focused on the single and binary adsorption of methylene blue(MB)and methyl orange(MO)from alcohol aqueous solution over rice husk based activated carbon(RHAC).The study of single dye adsorption equilibrium experiments found that the Langmuir adsorption model was consistent with the adsorption behavior of RHAC on MB and MO,indicating that it was a single layer adsorption.The adsorption behavior con-formed to the pscudo-second-order kinetic model.The binary dye adsorption experiments showed that the Lang-muir-Freundlich model could be applied to describe the adsorption behavior of RHAC on MB and MO.Comparation with the single dye system,the adsorption capacity on the binary dye system was larger,and there was"competitive adsorption"and"synergistic adsorption"effects existed.Meanwhile,the pseudo-second-order kinetic model also fit for the binary dye adsorption behavior.

生物质稻壳基多孔炭载铁催化剂实验设计

介绍一个利用生物质稻壳资源制备多孔炭负载铁催化剂的绿色化学综合实验。实验设计基于有机化学、物理化学与仪器分析等学科知识,采用高温碳化方法,将溶剂萃取和碱液溶解处理后的稻壳制备成多孔活性炭载体,负载铁催化剂用于合成气制液体燃料反应,实现了稻壳资源的综合利用。实验涉及的反应兼具综合性和设计性,符合绿色化学理念。通过本实验不仅可以培养学生的化学基本素养,也有助于强化学生的科学创新思维,锻炼学生的知识综合运用能力。

磷酸活化对活性炭及铅炭电池性能的影响

铅炭电池兼具铅酸电池和超级电容器的优点。为进一步提高铅炭电池的性能,以稻壳为碳源、磷酸(H_(3)PO_(4))为活化剂,制备铅炭电池用稻壳基活性炭,考察浸渍比、活化温度和活化时间等参数对活性炭物化特性及铅炭电池性能的影响。控制活化参数,可改变活性炭的孔隙结构:浸渍比越高,比表面积和介孔率越大;550℃的活化温度更适用于合成高介孔率的活性炭;当活化时间在90 min以上时,微孔、介孔倾向于塌陷成大孔。在浸渍比1.00∶3.85、活化温度550℃及活化时间90 min下合成的活性炭,兼具高比表面积(1 087.6 m^(2)/g)和高介孔率(85.31%),应用于负极中,可提高铅炭电池的高倍率部分荷电状态(HRPSoC)循环寿命:循环寿命高达13 738次,是空白电极的29.9倍。

活化剂对铁卟啉修饰的稻壳碳催化剂氧还原反应性能的影响

稻壳碳(RHC)材料由于其产量丰富,价格低廉,近年来已被应用于多种工业领域。阴极上电催化氧还原反应(ORR)的缓慢动力学是限制燃料电池性能的关键因素,用稻壳碳材料制备价格低廉的ORR催化剂具有良好的应用前景。对稻壳碳材料的制备条件进行优化,探究K2CO3、KOH两种活化剂对所制备铁卟啉修饰的稻壳材料ORR性能的影响。结果表明,在以稻壳碳(RHC)K 2CO3 KOH=133的比例进行活化处理时,得到的RHC材料具有最大的比表面积和更加适宜的孔结构,在铁卟啉衍生化后具有最优的ORR性能,其半波电位为0.865 V,具有与Pt/C相近的塔菲尔斜率,且ORR过程接近四电子还原。

Multiple Functional Biomass-Derived Activated Carbon Materials for Aqueous Supercapacitors, Lithium-Ion Capacitors and Lithium-Sulfur Batteries

Biomass-derived activated carbon electrode materials have been synthesized by carbonization and KOH activa- tion processes from an agriculture waste - rice husk, composed of organic compound and silica. The surface area of activated carbon reached 1098.1 m2/g mainly including mesopores and macropores due to the template effect of sil- ica in rice husk. Owing to the existence of mesopores and macropores, the as-obtained activated carbon materials can be used in aqueous supercapacitors, lithium-ion （Li-ion） capacitors and lithium-sulfur （Li-S） batteries. In KOH electrolyte, fast rate performance （as high as 2 V/s） was obtained due to the existence of ideal electrical double layer capacitance. In organic electrolyte, high voltage （2.5 V） was achieved. Activated carbon electrode for Li-ion capac- itor also showed capacity of 17 mAh/g at 100 mA/g with the high voltage range of 2.5 V. The capacities of sul- fur-activated carbon in Li-S batteries were 1230 and 970 mAh/g at the current densities of 0.1 and 0.2 C. The pre- sent results showed that activated carbon materials with mesopores were good host to immobilize polysulfides.

稻壳制备活性炭联产二氧化硅工艺研究

当前,随着社会经济的不断发展,人们对于稻壳的二次利用及节能意识开始不断提升,稻壳是稻谷进行加工后的一种副产品,以往均是作为废弃物品进行处理的,最多也只是被用于燃料,在一定程度上造成了资源的浪费,同时还会对环境带来严重影响和污染,基于此,对稻壳进行加工利用是当下实现可持续环保理念发展的重要课题。首先简单阐述了稻壳的相关特性,然后就稻壳制备活性炭及二氧化硅进行深入研究。

由稻壳制备高比表面积活性炭

以稻壳为原料 ,KOH为活化剂制备了高比表面积活性炭 ,其比表面积超过 30 0 0 m2 /g,且孔径均一 。

碱炭比及活化温度对稻壳活性炭极微孔的影响

采用N2吸附、CO2吸附和热重红外联用等技术手段,考察了在KOH活化稻壳炭的过程中碱炭比和活化温度对活性炭极微孔的影响。结果表明：在不同碱炭比（0.6︰1~3︰1）和活化温度（640~780℃）下制备的稻壳活性炭,极微孔主要分布在0.42~0.70 nm。当碱炭比增加时,极微孔孔容先增大后减小;而当活化温度升高时,极微孔孔容呈降低趋势。极微孔率随碱炭比或活化温度的升高而单调递减。在活化温度为640℃、碱炭比为1：1时,可得极微孔孔容为0.149 m L/g、极微孔率达36.3%的微孔活性炭。活性炭的极微孔孔容与其在104 Pa时的CO2吸附量高度线性相关。

稻壳制活性炭及其对污水中铬的吸附能力研究

研究了以稻壳为原料用磷酸活化法制备粉状活性炭的条件,并探讨了稻壳活性炭对水中铬离子的吸附性能。结果表明废弃稻壳在氮气保护下,以每分钟升温10℃的速率加热到400℃进行预炭化,再在800℃条件下活化所制备的活性炭对废水中重金属铬离子具有较强的吸附性能。这为稻壳的综合利用、提高农副产品的价值及解决环境污染提供了一条途径。

稻壳炭提取SiO_2及制备活性炭联产工艺

为了利用气化发电的固体产物稻壳炭,通过单因素试验,研究了稻壳炭同时提取二氧化硅及制备活性炭工艺技术,得出优化的工艺条件:质量分数20%的K2CO3溶液与稻壳炭原料的液固比为15mL/g,煮溶温度100℃,煮溶时间3.5h;稻壳炭的炭化温度是450℃,活化温度850℃,活化时间2h;SiO2的陈化温度为3℃、陈化时间3h。此条件下制备的稻壳基活性炭得率39.34%、碘吸附值978.35mg/g、亚甲基兰吸附值12mL/0.1g;二氧化硅得率25.77%、白度89.91%。试验表明该工艺制备出的稻壳基活性炭及二氧化硅产品的质量均达到了国家标准的要求,同时为稻壳炭的高效、无公害及资源化利用提供了一条可循的途径。

稻壳与脱硅稻壳活性炭特性及对有机物吸附

以稻壳为原料,同时制备脱硅稻壳,采用ZnCl2-CuCl2复合活化剂制备活性炭,并对所制备的稻壳活性炭(RAC)与脱硅稻壳活性炭(FAC)的孔结构和表面化学性质进行了分析,而后将其应用于对水中有机物的去除,同时研究了其吸附特性。结果表明:所制得的稻壳活性炭比表面积达到了1 924 m2/g,而稻壳经过脱硅处理制得的活性炭比表面积达到了2 433 m2/g。脱硅稻壳表面具有更多种类的官能团存在。稻壳与脱硅稻壳活性炭在碱性条件下有利于品红的吸附,并且适用于高盐度条件下品红的吸附;在初始pH值为7,初始质量浓度为400 mg/L,投加量为0.8 mg/g时,稻壳活性炭和脱硅稻壳活性炭对有机物的吸附量分别达到439和483 mg/g;吸附等温模型符合Langmuir等温式;吸附动力学以及脱附研究显示稻壳与脱硅稻壳活性炭对品红的吸附过程主要由化学吸附控制。

稻壳基脱硅活性炭的制备及其对油气吸附性能研究

利用碳酸钠对稻壳进行水热脱硅,得到脱硅稻壳炭(RHC),并以RHC为原料,分别使用一定浓度的NaOH、H3PO4和ZnCl2在一定温度下对RHC进行活化改性制得稻壳基脱硅活性炭(RHAC)吸附剂,并依据RHAC对正己烷的静态吸附率进行实验条件优选,并对优选条件下制得的RHAC进行油气动态吸附实验及其物性参数表征。结果表明:H3PO4溶液活化RHC制备RHAC为最佳活化剂,最优实验条件为H3PO4溶液浓度34%,浸渍时间6h,活化时间60min,活化温度500℃;RHAC对油气的饱和吸附率为26.39%,比表面积为823.68m2/g,总孔容为0.645cm3/g,平均孔径为2.163nm。

稻壳基活性炭电极材料制备及其电化学性能研究

以稻壳为原料,氢氧化钠为活化剂,制备活性炭。进一步将该活性炭作为电极材料,以氢氧化钾溶液为电解液,组装超级电容器。采用X射线衍射(XRD)、氮气吸附脱附(BET)、扫描电镜(SEM)等手段,分析了不同活化温度对活性炭的比表面积及孔结构的影响,并利用恒流充放电、循环伏安等方法研究了电容器的电化学性能。结果表明:800℃活化下活性炭的比表面积最佳,为2760 m^2/g,孔结构发达。此条件下,在6 mol/L的KOH电解液中,活性炭电容器比电容达267.2 F/g,等效内阻仅2.2Ω,倍率性能好。经过5000次循环后,其电容保持率仍有83.7%,表明该稻壳基活性炭电极具有优异的充放电可逆性和循环稳定性。

稻壳基活性炭制备及其对重金属吸附研究

活性炭吸附法是重金属废水处理的重要方法。利用廉价的稻壳,选择氢氧化钠和磷酸作活化剂制备活性炭,测定了稻壳基活性炭的比表面积、亚甲基蓝吸附值、碘吸附值、苯酚吸附值和等电点。利用制备的稻壳基活性炭吸附溶液中的Cd、Cu、Zn,研究了不同稻壳基活性炭对Cd、Cu、Zn的吸附差异,并利用X射线衍射仪分析了稻壳基活性炭中微晶体结构。结果表明,氢氧化钠作活化剂时,浸渍方式不影响稻壳基活性炭品质,2种活化方式(即氢氧化钠颗粒直接混合后烧制和氢氧化钠浸渍后烧制)所制备的稻壳基活性炭达到或接近木质净水用活性炭一级品标准,对Cd、Cu、Zn吸附量基本表现为Cu>Cd>Zn;磷酸作活化剂时,制备的稻壳基活性炭受稻壳粉碎粒径影响显著,粒径越小,越不利于对重金属的吸附,这与活性炭的等电点和含硅量有关。

稻壳联产纳米白炭黑与活性炭的研究

研究了由稻壳同时制备纳米白炭黑和活性炭的最佳工艺条件,并对提高产品质量的主要因素作了初步探讨。由滤液硅酸钠溶液制备纳米白炭黑可采用氯化铵中和,聚乙二醇-6000作表面活性剂,所得纳米白炭黑质量完全符合国家标准。筛选出了反应的最佳工艺条件:与稻壳灰反应的NaOH的浓度为2.5mol/L,反应时间为4h,反应温度100℃。在此条件下,SiO2的提取率为95%,白炭黑的白度在90%以上,所得活性炭的亚甲蓝吸附值为140ml/g以上。制备的纳米白炭黑制品为白色絮状沉淀,经X射线衍射分析,结果表明制品为无定形非晶态物质。TEM分析可知,粒子呈球形,粒径为40nm左右。红外光谱分析发现,纳米白炭黑中的SiO2为无定形水合二氧化硅。

载银及酸处理改性对稻壳活性炭吸附脱硫性能的影响

将稻壳炭化后经KOH浸泡及焙烧活化制得稻壳活性炭,再利用超声波辅助AgNO_3溶液浸渍及HNO_3酸处理,制得改性稻壳活性炭。采用XRD、SEM、BET、FT-IR等手段表征样品,利用含噻吩模拟油填充床实验,研究改性稻壳活性炭吸附脱硫性能,并利用吸附模型方程对吸附过程进行热力学及动力学分析。结果表明,AgNO_3浸渍并焙烧后形成Ag微晶颗粒分散于活性炭表面,HNO_3酸处理会增加活性炭表面酸性含氧官能团数量;改性后稻壳活性炭吸附脱硫能力增加,4种活性炭的吸附脱硫能力从大到小依次为Ag-HNO_3-AC、HNO_3-AC、Ag-AC、RH-AC;Langmuir等温吸附模型、准n阶动力学吸附模型、Weber-Morris内扩散模型能较好地说明改性稻壳活性炭吸附噻吩的作用机理。