The reuse of biosludge as an adsorbent from a petrochemical wastewater treatment plant

Biosludge was obtained from a petrochemical industry's biological wastewater treatment plant. Zinc chloride (ZnCl2) was used as a sludge activation agent during the pyrolytic process. Scanning electron microscope (SEM) image photographs, element composition, surface functional group, and pore structure were analyzed for the sludge adsorbent characteristics. Results indicated the proper ZnCl2-immersed concentration, pyrolytic temperature, and time could produce adsorbent from the biosludge. The optimal conditions for a larger surface area adsorbent were 3 M ZnCl2-immersed sludge pyrolyzed at 600 degrees C for 30 min and washed with 3 N hydrochloric acid (HCl) solution and distilled water. The predominant pore size of the sludge adsorbent was the mesopore.     

Adsorption Characteristics of Benzene on Biosolid Adsorbent and Commercial Activated Carbons

Abstract

This study selected biosolids from a petrochemical waste-water treatment plant as the raw material. The sludge was immersed in 0.5-5 M of zinc chloride (ZnCl₂) solutions and pyrolyzed at different temperatures and times. Results indicated that the 1-M ZnCl₂-immersed biosolids pyrolyzed at 500 °C for 30 min could be reused and were optimal biosolid adsorbents for benzene adsorption. Pore volume distribution analysis indicated that the mesopore contributed more than the macropore and micropore in the biosolid adsorbent. The benzene adsorption capacity of the biosolid adsorbent was 65 and 55% of the G206 (granular-activated carbon) and BPL (coal-based activated carbon; Calgon, Carbon Corp.) activated carbons, respectively. Data from the adsorption and desorption cycles indicated that the benzene adsorption capacity of the biosolid adsorbent was insignificantly reduced compared with the first-run capacity of the adsorbent; therefore, the biosolid adsorbent could be reused as a commercial adsorbent, although its production cost is high.     

Emission factor of exhaust gas constituents during the pyrolysis of zinc chloride immersed biosolid

Pyrolysis enables ZnCl₂ immersed biosolid to be reused, but some hazardous air pollutants are emitted during this process. Physical characteristics of biosolid adsorbents were investigated in this work. In addition, the constituents of pyrolytic exhaust were determined to evaluate the exhaust characteristics. Results indicated that the pyrolytic temperature was higher than 500 °C, the specific surface area was >900 m²/g, and the total pore volume was as much as 0.8 cm³/g at 600 °C. For non-ZnCl₂ immersed biosolid pyrolytic exhaust, VOC emission factors increased from 0.677 to 3.170 mg-VOCs/g-biosolid with the pyrolytic temperature increase from 400 to 700 °C, and chlorinated VOCs and oxygenated VOCs were the dominant fraction of VOC groups. VOC emission factors increased about three to seven times, ranging from 1.813 to 21.448 mg/g for pyrolytic temperatures at 400–700 °C, corresponding to the mass ratio of ZnCl₂ and biosolid ranging from 0.25–2.5.     

Preparation of carbonaceous adsorbent from straw and its adsorption performance for H2S removal

ABSTRACT

Activated carbonaceous were prepared from high-carbon, abandoned straw biomass. With hydrogen sulfide gas as the target pollutant, single factor experiments were employed to assess the effects of activator type, activation temperature, activation time, and liquid-material ratio on the adsorption performance of the prepared carbonaceous adsorbent. The materials were characterized using elemental analysis, SEM, FTIR, and BET. The results showed -OH, -CH-, and -C = O groups exist on the surface of the prepared adsorbent, specific surface area can reach 1104.84 m²?g^?1, total pore volume can reach 0.261 cm³?g^?1 and, where the pore volume is greater than 80%, well-developed pore structures were present that facilitated adsorption. The experimental results showed the adsorption time could reach 198 min with optimal ZnCl₂ activator concentration (30%), carbonization temperature (550°C), and liquid-to-material ratio (3:1). Compared with the existing activated carbon adsorbents, the adsorption effects and preparation cost of this absorbent are advantageous, and the absorbent has prospects for broad market application.     

微波法制备污泥活性炭研究

采用微波加热法,以污水厂剩余污泥为原料,磷酸为污泥活化剂制备污泥活性炭.微波功率、辐照时间和磷酸浓度对污泥活性炭吸附性能具有显著影响,在最佳工艺条件微波功率480 W、辐照时间315 s和磷酸浓度40%条件下制得的活性炭碘值301 mg/g,比表面积168 m2/g,污泥中重金属绝大部分被固化.与传统商品炭相比,污泥炭孔隙结构以中孔为主.利用该活性炭处理城市生活污水处理厂出水,COD去除率可达87%以上,污泥炭的吸附等温线用Langmuir等温吸附模型进行描述.     

污泥吸附剂对3种染料吸附动力学的研究

以污水厂脱水污泥、锯末和焦油的混合物为原料，选择ZnCl₂为活化剂制备出过渡孔发达、强度大的污泥吸附剂（S-AC）。借助BET、FT-IR等现代分析测试方法对污泥吸附剂进行表征，同时，研究了吸附剂对酸性大红、中性红和碱性品红吸附动力学行为。结果表明，制得的污泥吸附剂BET比表面积为358 m²/g，强度大于89%。吸附剂的动力学数据均符合伪二阶动力学方程、液膜扩散方程和颗粒内扩散方程，其中液膜扩散为吸附剂对酸性大红吸附过程的主控步骤，颗粒内扩散为吸附剂对中性红和碱性品红吸附过程的主控步骤。     

Adsorption characteristics of benzene on biosolid adsorbent and commercial activated carbons

This study selected biosolids from a petrochemical waste-water treatment plant as the raw material. The sludge was immersed in 0.5-5 M of zinc chloride (ZnCl2) solutions and pyrolyzed at different temperatures and times. Results indicated that the 1-M ZnCl2-immersed biosolids pyrolyzed at 500 degrees C for 30 min could be reused and were optimal biosolid adsorbents for benzene adsorption. Pore volume distribution analysis indicated that the mesopore contributed more than the macropore and micropore in the biosolid adsorbent. The benzene adsorption capacity of the biosolid adsorbent was 65 and 55% of the G206 (granular-activated carbon) and BPL (coal-based activated carbon; Calgon, Carbon Corp.) activated carbons, respectively. Data from the adsorption and desorption cycles indicated that the benzene adsorption capacity of the biosolid adsorbent was insignificantly reduced compared with the first-run capacity of the adsorbent; therefore, the biosolid adsorbent could be reused as a commercial adsorbent, although its production cost is high.     

Low-cost adsorbent prepared from sewage sludge and corn stalk for the removal of COD in leachate

Sewage sludge (SS) with corn stalk (CS) was used to prepare SS-based activated carbon (SAC) by pyrolysis with ZnCl₂. The effects of mixing ratio on surface area and pore size distribution, elemental composition, surface chemistry, and morphology were investigated. The results demonstrated that the addition of CS into SS samples improved the surface area (from 92 to 902 m²/g) and the microporosity (from 1.2 to 4.1 %) of the adsorbents and, therefore, enhancing the adsorption performance. The removal of leachate chemical oxygen demand (COD) was also determined. It was found that the COD removal rate reached 85 % at pH 4 with the SAC (90 wt% CS) dosage of 2 % (g/mL) and an adsorption time of 40 min. The adsorption experimental data were fitted by both Langmuir and Freundlich adsorption isotherms. Long-chain alkanes and refractory organics were found in raw leachate, but could be removed by SAC largely.     

Application of magnetically modified sewage sludge ash (SSA) in ionic dye adsorption

Incineration is a traditional method of treating sewage sludge and the disposal of derived ash is a problem of secondary waste treatment. In this study, sewage sludge ash (SSA) was coated with ferrite through a ferrite process and then used as an adsorbent for ionic dyes (methylene blue [MB] and Procion Red MX-5B [PR]). The modified SSA possessed surface potential that provided electrostatic attraction toward MB and PR. Adsorbent FA10 (named on the basis of being produced from 10 g of SSA in the ferrite process) was used for the adsorption of MB. Ideal pH for adsorption was 9.0 and maximum adsorption capacity based on Langmuir isotherm equation was 22.03 mg/g. Adsorbent FA2.5 (named on the basis of being produced from 2.5 g of SSA in the ferrite process) was used for PR adsorption. Ideal pH for adsorption was 3.0 and the maximum adsorption capacity (calculated as above) was 28.82 mg/g. Kinetic results reveal that both MB and PR adsorption fit the pseudo-second-order kinetic model better than the pseudo-first-order model. The values of activation energy calculated from rate constants were 61.71 and 9.07 kJ/mol for MB and PR, respectively.

Implications:

Magnetic modified adsorbent could be synthesized from sewage sludge ash (SSA). In this study, the adsorption ability of SSA toward ionic dye (methylene blue [MB] and Procion Red MX-5B [PR]) was enhanced by ferrite process. The synthesized Fe₃O₄ can act as an active site and provide electrostatic attraction toward cationic dye and anionic dye at different pH. The application of magnetic modified adsorbent in wastewater treatment can not only recycle the SSA, but also make SSA become an environmentally friendly material.     

Performance Evaluation of Waste Activated Carbon on Atrazine Removal from Contaminated Water

Abstract

In this study, the potential of spent activated carbon from water purifier (Aqua Guard, India) for the removal of atrazine (2 chloro-4 ethylamino-6-isopropylamino-1, 3, 5 triazine) from wastewaters was evaluated. Different grades of spent activated carbon were prepared by various pretreatments. Based on kinetic and equilibrium study results, spent activated carbon with a grain size of 0.3–0.5 mm and washed with distilled water (designated as WAC) was selected for fixed column studies. Batch adsorption equilibrium data followed both Freundlich and Langmuir isotherm. Fixed bed adsorption column with spent activated carbon as adsorbent was used as a polishing unit for the removal of atrazine from the effluent of an upflow anaerobic sludge blanket (UASB) reactor treating atrazine bearing domestic wastewater. Growth of bacteria on the surface of WAC was observed during column study and bacterial activity enhanced the effectiveness of adsorbent on atrazine removal from wastewater.     

污泥活性炭固定床吸附甲苯

采用ZnCl2化学活化法制备的污泥活性炭用于固定床吸附甲苯实验,研究了吸附剂床层厚度、甲苯初始浓度、气体线速等操作条件对其吸附性能的影响,并建立了污泥活性炭吸附甲苯的传质模型,计算不同操作条件下的传质区长度和物质总传质系数。结果表明,当床层厚度从3 cm增加到7 cm,传质区长度基本不变,物质总传质系数增加了66.66%;当甲苯初始浓度增大3.36倍,传质区长度增加了17.19%,而物质总传质系数降低了22.05%;在实验流速范围内,气体线速变为原来的2倍,物质总传质系数增加了65.27%,说明污泥活性炭对甲苯吸附属于外扩散控制。     

Preparation of Activated Carbons from Raw and Biotreated Agricultural Residues for Removal of Volatile Organic Compounds

ABSTRACT

Activated carbons with diverse physical and chemical properties were produced from four agriculture residues, including raw barley husk, biotreated barley husk, rice husk, and pistachio shell. Results showed that with adequate steam activation (30–90 min, 50% H₂O_(g)/50% N₂), activated carbons with surface areas between 360 and 950 m² g^?1 were developed. Further increases in the activation time destroyed the pore structure of activated carbons, which resulted in a decrease in the surface area and pore volume. Biotreated agricultural residues were found to be suitable precursors for producing mesoporous activated carbons. The oxygen content of activated carbons increased with increasing activation time. Results from X-ray photoelectron spectroscopy examination further suggested that H₂O molecules react with the carbon surface, enhancing the deconvoluted peak area of carbonyl and carboxyl groups. Equilibrium adsorption of toluene indicated that the adsorption capacities increased with an increase in the inlet toluene concentration and a decrease in temperature. The adsorption isotherms were successfully fitted with Freundlich, Langmuir, and Dubinin– Radushkevich equations. Activated carbons derived from agricultural residues appear to be more applicable to adsorb volatile organic compounds at a low concentration and high-temperature environment.

IMPLICATIONS This paper presents data on the preparation of activated carbons from agricultural residues, especially the waste from biohydrogen generation. Experimental results indicated that with proper carbonization and steam activation, activated carbons with diverse characteristics can be produced from various agricultural residues. The resulting activated carbons effectively adsorb toluene. This work provides useful information for reutilization of these agricultural residues, helping in decreasing the cost of biological waste treatment and providing a cost-effective alternative to conventional adsorbent production and application.     

Chronic toxicity of ZnO nanoparticles, non-nano ZnO and ZnCl2 to Folsomia candida (Collembola) in relation to bioavailability in soil

The chronic toxicity of zinc oxide nanoparticles (ZnO-NP) to Folsomia candida was determined in natural soil. To unravel the contribution of particle size and free zinc to NP toxicity, non-nano ZnO and ZnCl₂ were also tested. Zinc concentrations in pore water increased with increasing soil concentrations, with Freundlich sorption constants K_f of 61.7, 106 and 96.4 l/kg (n = 1.50, 1.34 and 0.42) for ZnO-NP, non-nano ZnO and ZnCl₂ respectively. Survival of F. candida was not affected by ZnO-NP and non-nano ZnO at concentrations up to 6400 mg Zn/kg d.w. Reproduction was dose-dependently reduced with 28-d EC50s of 1964, 1591 and 298 mg Zn/kg d.w. for ZnO-NP, non-nano ZnO and ZnCl₂, respectively. The difference in EC50s based on measured pore water concentrations was small (7.94-16.8 mg Zn/l). We conclude that zinc ions released from NP determine the observed toxic effects rather than ZnO particle size.     

Capture of CO2 on γ-Al2O3 materials prepared by solution-combustion and ball-milling processes

A series of porous γ-Al₂O₃ materials was prepared by solution-combustion and ball-milling processes. The as-prepared powders were physicochemically characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and N₂ physisorption measurements and their performances in CO₂ adsorption at different pressures (0.5 to 1.5 MPa) and temperatures (40 to 60ºC) were investigated. It was found that γ-Al₂O₃ synthesized by the solution-combustion process and ball milled at 10 hr exhibited the best CO₂ adsorption performance at 60ºC and 1.5 MPa, achieving a maximum of 1.94 mmol/g compared to the four studied materials, as a result of their interesting microstructure and surface properties (i.e., nanocrystallinity, specific surface area, narrow pore size distribution, and large total pore volume). Our study shows that the γ-Al₂O₃ prepared by solution combustion followed by ball milling presents a fairly good potential adsorbent for efficient CO₂ capture.

Implications: In this work, γ-Al₂O₃ materials were successfully obtained by solution combustion and modified via ball milling. These improved materials were systematically investigated as solid adsorbents of accessible surface areas, large pore volumes, and narrow pore size distribution for the CO₂ capture. These studied solid adsorbents can provide an additional contribution and effort to develop an efficient CO₂ capture method as means of alleviating the serious global warning problem.     

Preparation and characterization of activated carbons from tobacco stem by chemical activation

Activated carbons were prepared from tobacco stem by chemical activation using potassium hydroxide (KOH), potassium carbonate (K₂CO₃), and zinc chloride (ZnCl₂). The effects of the impregnation ratio (activating agent/precursor) and activating agents on the physical and chemical properties of activated carbons were investigated. The textual structure and surface properties of activated carbons were characterized by nitrogen (N₂) adsorption isotherm, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), x-ray photoelectron spectroscopy (XPS), and thermogravimetry (TG). ZnCl₂, acting as a superior activating agent compared to the others, produced much more porosity. The maximum specific surface area reached 1347 m²/g, obtained by ZnCl₂ activation with an impregnation ratio of 4.0. Moreover, ZnCl₂ activation yielded products with an excellent thermostability, attributed to different activation mechanisms. Various oxygen functions were detected on the activated carbon surface, and hydroxyl and ester groups were found to be in the majority.

Implications: Tobacco stem, the residue from cigarette manufacturing, is usually discarded as waste, leading to serious resource waste and environmental problems. This study provides an effective utilization available for this solid residue by using it as the starting material in the preparation of activated carbon with chemical activation. Activated carbons with high specific area and various surface functions have been prepared, and the effects of the amount and type of activating agents on the physical and chemical properties of activated carbon were investigated as well.     

Production of Activated Carbons from Pyrolysis of Waste Tires Impregnated with Potassium Hydroxide

ABSTRACT

Activated carbons were produced from waste tires using a chemical activation method. The carbon production process consisted of potassium hydroxide (KOH) impregnation followed by pyrolysis in N₂ at 600-900 °C for 0-2 hr. The activation method can produce carbons with a surface area (SA) and total pore volume as high as 470 m²/g and 0.57 cm³/g, respectively. The influence of different parameters during chemical activation, such as pyrolysis temperature, holding time, and KOH/tire ratio, on the carbon yield and the surface characteristics was explored, and the optimum preparation conditions were recommended. The pore volume of the resulting carbons generally increases with the extent of carbon gasified by KOH and its derivatives, whereas the SA increases with degree of gasification to reach a maximum value, and then decreases upon further gasification.     

MCM-41介孔分子筛的合成及其对铜离子的吸附性能简

以微硅粉为硅源，CTAB和PEG-6000为模板剂，合成MCM-41介孔分子筛。采用XRD、N₂吸附-脱附曲线、FTIR以及TEM表征了其结构、比表面积、孔径分布及晶体形貌，并且以该样品为吸附剂，对含Cu²⁺的溶液进行了静态吸附实验。结果表明，以微硅粉为硅源成功合成了具有典型六方排列孔道结构的MCM-41，其比表面积为869.5 m²/g，孔容为0.97 cm³/g，平均孔径为3.3 nm；溶液pH为5~6时，MCM-41对Cu²⁺的去除效果最好；MCM-41对Cu²⁺的最大吸附吸附容量36.3 mg/g；MCM-41对Cu²⁺的吸附性能符合Langmuir吸附方程的特征。动力学研究表明，该过程符合准二级动力学模型。     

Gaseous Ammonia Uptake in Compost Biofilters as Related to Compost Water Content

Abstract

Sewage sludge and yard waste compost were used as biofilter materials and tested with respect to their capacity for removing ammonia from air at different water contents. Ammonia removal was measured in biofilters containing compost wetted to different moisture contents ranging from air dry to field capacity (maximum water holding capacity). Filters were operated for 15 days and subsequently analyzed for NH₃/NH₄ ⁺, NO₂ ^-, and NO₃ ^-. The measured nitrogen species concentration profiles inside the filters were used to calculate ammonia removal rates. The results showed that ammonia removal is strongly dependent on the water content in the filter material. At gravimetric water contents below 0.25 g H₂O g solids^-1 for the yard waste compost and 0.5 g H₂O g solids^-1 ammonia removal rates were very low but increased rapidly above these values. The sewage sludge compost filters yielded more than twice the ammonia removal rate observed for yard waste compost likely because of a high initial concentration of nitrifying bacteria originating from the wastewater treatment process and a high air-water interphase surface area that facilitates effective ammonia dissolution and transport to the biofilm.     

Migration of polycyclic aromatic hydrocarbons (PAHs) in urban treatment sludge to the air during PAH removal applications

In the present study, the amounts of polycylic aromatic hydrocarbons (PAHs) penetrating into air during PAH removal applications from the urban treatment sludge were investigated. The effects of the temperature, photocatalyst type, and dose on the PAH removal efficiencies and PAH evaporation were explained. The sludge samples were taken from an urban wastewater treatment plant located in the city of Bursa, with 585,000 equivalent population. The ultraviolet C (UV-C) light of 254 nm wavelength was used within the UV applications performed on a specially designed setup. Internal air of the setup was vacuumed through polyurethane foam (PUF) columns in order to collect the evaporated PAHs from the sludge during the PAH removal applications. All experiments were performed with three repetitions. The PAH concentrations were measured by gas chromatography–mass spectrometry (GC-MS). It was observed that the amounts of PAHs penetrating into the air were increased with increase of temperature, and more than 80% of PAHs migrated to the air consisted of 3-ring compounds during the UV and UV-diethylamine (DEA) experiments at 38 and 53 °C. It was determined that 40% decrease was ensured in Σ₁₂ (total of 12) PAH amounts with UV application and 13% of PAHs in sludge penetrated into the air. In the UV-TiO₂ applications, a maximum 80% of Σ₁₂ PAH removal was obtained by adding 0.5% TiO₂ of dry weight of sludge. The quantity of PAH penetrating into air did not exceed 15%. UV-TiO₂ applications ensured high levels of PAH removal in the sludge and also reduced the quantity of PAH penetrating into the air. Within the scope of the samples added with DEA, there was no increase in PAH removal efficiencies and the penetration of PAHs into air was not decreased. In light of these data, it was concluded that UV-TiO₂ application is the most suitable PAH removal alternative that restricts the convection of PAH pollution.

Implications: Polycyclic aromatic hydrocarbon (PAH) evaporation rates from sludge samples obtained from an urban wastewater treatment plant were investigated here for the first time by employing removal applications. TiO₂ and diethylamine were used as photocatalysts in this study. A special device was designed and successfully used in this study. Treatment sludge can be a significant source of PAHs for the atmosphere. The data highlight the need for removal of PAHs in treatment sludge via methods limiting their evaporation to the air. It was observed that UV-TiO₂ application was the most suitable PAH removal alternative that restricts the convection of PAH pollution.     

A two-generational reproductive toxicity study of zinc in rats

A two-generation reproductive toxicity study of zinc chloride (ZnCl₂) was conducted in rats. F_o male and female rats were administered 0.00 (control), 7.50 (low), 15.00 (mid) and 30.00 (high) mg/kg/day of ZnCl₂. Selected F₁ male and female rats were exposed to the same doses received by their parents (F_o). Exposure of F₀ parental rats to ZnCl₂ showed significant reduction in fertility, viability (days 0 and 4), and the body weight of F₁ pups from the high-dose group but caused no effects on litter size, weaning index, and sex ratio. Similarly, the continued exposure of F₁ parental rats to ZnCl₂ also reduced fertility, liter size, viability (day 0), and the body weight of F₂ pups within the high-dose group but caused no effects on weaning index and sex ratio. Exposure of ZnCl₂ to F₀ and F₁ parental males resulted in a significant reduction in their body weights, and the F₀ and F₁ parental females did not show any significant difference in their body weights compared to their control groups. However, the postpartum dam weights of both F₀ and F₁ female rats were significantly reduced compared to their controls. Exposure of ZnCl₂ to F_o and F₁ generation parental rats did not produce any significant change of their clinical signs as well as their clinical pathology parameters, except the alkaline phosphotase (ALK) level, which showed an upward trend in both sexes of both generations. Exposure of ZnCl₂ to F₀ rats resulted in a reduction of brain, liver, kidney, spleen and seminal vesicles weights of males and in the spleen and uterus of females. Similarly, exposure of F₁ rats to ZnCl₂ also resulted in reduction of brain, liver, kidney, adrenal, spleen, prostate and seminal vesicles weights of males and in spleen and uterus of females. ZnCl₂ exposure resulted in grossly observed gastro-intestianla (GI) tract, lymphoreticular/hematopoietic, and reproductive tract lesions in parental rats in both generations. Reduced body fat was also recorded in F₁ parental rats.