Investigation of CO2 adsorption by bagasse-based activated carbon

Bagasse-based activated carbon (BAC) and amine-modified BAC were prepared and investigated for CO₂ adsorption capacity. Modifying BAC with amines resulted in a decrease of surface area, but the decreasing magnitude varied depending on type and loading rate of amines. At room temperature, the unmodified BAC was able to adsorb more CO₂ than the amine-modified BAC. This ability was related to the higher surface area of unmodified than that of the modified BAC. When temperature increased, CO₂ adsorption capacity of all absorbents was decreased. However, above 323 K and a concentration of CO₂ lower than 30% v/v, the BAC modified with PEI at 5 and 25 wt% showed higher adsorption capacity. Among all adsorbents under 15% CO₂ and 348 K, BAC-PEI25 showed the highest adsorption capacity (0.20 mmol/g).     

An Approach for Assessment of Compaction Curves of Fine Grained Soils at Various Energies Using a One Point Test

Compaction curves of soils are essential for establishing practical and reliable criteria for an effective control of field compaction. This paper deals with the development of a practical method of assessing laboratory compaction curves of fine-grained soils. It is found that for a given fine-grained soil compacted at a particular compaction energy, the relationships between water content (w) and degree of saturation (S) are represented by power function, which are w=A_dS^B_d and w=A_wS^B_w for the dry and the wet sides of optimum, respectively (where A_d, A_w, B_d and B_w are constant). The B_d and B_w values and optimum degree of saturation (ODS) are mainly dependent upon soil type irrespective of compaction energy. The A_d and A_w values decrease with the logarithm of compaction energy and the decrease rates are practically the same for any compacted fine-grained soil. This leads to a simple and rational method to assess the compaction curve wherein the compaction energy varies over a wide range using a one point test (a single test). Assuming that fine-grained soils compacted under standard Proctor energy behave in agreement with Ohio's curves, the modified Ohio's curves for the other three compaction energy levels (296.3, 1346.6 and 2693.3 kJ/m³) are developed based on the proposed method. These curves can be used to assess the entire compaction curves at the required compaction energy based on a single set data of dry unit weight and water content.     

Production, composition and Pb2+ adsorption characteristics of capsular polysaccharides extracted from a cyanobacterium Gloeocapsa gelatinosa

Pb²⁺ adsorption by the living cells of the cyanobacterium Gloeocapsa gelatinosa was studied. Cyanobacterial cells with intact capsular polysaccharide (CPS) showed 5.7 times higher Pb adsorption capacity than that of cells without CPS. The adsorbed Pb was desorbed by EDTA, indicating that Pb²⁺ adsorption occurred mainly on cell surface. Production, sugar content and ability of CPS to remove Pb²⁺ were then studied in details. CPS production by G. gelatinosa increased when culture time was prolonged. The maximum CPS production was 35.43 mg g⁻¹ dry weight after 30-day cultivation. Xylose, arabinose, ribose, rhamnose, galactose, glucose, mannose and fructose were the neutral sugars presented in CPS of G. gelatinosa. Acidic sugars including galacturonic and glucuronic acids were also found in CPS. The amount and composition of G. gelatinosa's CPS varied according to its growth phase and culture conditions. The highest amount of acidic sugars was produced when cultured under low light intensity. The extracted CPS rapidly removed Pb²⁺ from the solution (82.22±4.82 mg Pb²⁺ per g CPS), directly demonstrating its roles in binding Pb²⁺ ions. Its ability to remove Pb²⁺ rapidly and efficiently, to grow under sub-optimal conditions (such as low pH and low light intensity), and to produce high amount of CPS with acidic sugars, leads us to conclude that G. gelatinosa is a potential viable bioadsorber for mildly acidic water contaminated with Pb²⁺.     

Catalytic cracking reaction of used lubricating oil to liquid fuels catalyzed by sulfated zirconia

The conversion of used lubricating oil to transport fuel by direct cracking is a suitable way to dispose of waste oil. The aim of this research was to study the catalytic cracking of used lubricating oil, and thus change its classification from a waste produce to a liquid fuel as a new alternative for the replacement of petroleum fuels. The experiments were carried out in a 70-cm³ batch microreactor at a temperature of 648-698 K, initial hydrogen pressure of 1-4 MPa, and reaction time of 10-90 min over sulfated zirconia as a catalyst. The conditions that gave the highest conversion of naphtha (~20.60%) were a temperature of 698 K, a hydrogen pressure of 2 MPa, and a reaction time of 60 min, whereas, under the same conditions, kerosene, light gas oil, gas oil, long residues, hydrocarbon gases, and a small amounts of solids were present (~9.04%, 15.61%, 5.00%, 23.30%, 25.58%, and 0.87%, respectively). The liquid product consisted of C₇-C₁₅ of n-paraffins, C₇-C₉ of branched chain paraffin and aromatic compounds such as toluene, ethylbenzene and xylene. The kinetic study reveals that the catalytic cracking of waste lubricating oil follows a second order reaction, and the kinetic model is defined as k(s⁻¹)=2.88×10⁴exp[−(103.68 kJmol⁻¹)/(RT)].