Amination of biochar surface from watermelon peel for toxic chromium removal enhancement

Watermelon peel residues were used to produce a new biochar by dehydration method. The new biochar has undergone two methods of chemical modification and the effect of this chemical modification on its ability to adsorb Cr(VI) ions from aqueous solution has been investigated. Three biochars, Melon-B, Melon-BO-NH_2 and Melon-BO-TETA, were made from watermelon peel via dehydration with 50% sulfuric acid to give Melon-B followed by oxidation with ozone and amination using ammonium hydroxide to give Melon-BO-NH_2 or Triethylenetetramine(TETA) to give Melon-BO-TETA. The prepared biochars were characterized by BET, BJH,SEM, FT-IR, TGA, DSC and EDAX analyses. The highest removal percentage of Cr(VI) ions was 69% for Melon-B,98% for Melon-BO-NH_2 and 99% for Melon-BO-TETA biochars of 100 mg·L~(-1) Cr(VI) ions initial concentration and 1.0 g·L~(-1) adsorbents dose. The unmodified biochar(Melon-B) and modified biochars(Melon-BO-NH_2 and Melon-BO-TETA) had maximum adsorption capacities(Qm) of 72.46, 123.46, and 333.33 mg·g~(-1), respectively.The amination of biochar reduced the pore size of modified biochar, whereas the surface area was enhanced.The obtained data of isotherm models were tested using different error function equations. The Freundlich,Tempkin and Langmuir isotherm models were best fitted to the experimental data of Melon-B, Melon-BO-NH_2 and Melon-BO-TETA, respectively. The adsorption rate was primarily controlled by pseudo-second–order rate model. Conclusively, the functional groups interactions are important for adsorption mechanisms and expected to control the adsorption process. The adsorption for the Melon-B, Melon-BO-NH_2 and Melon-BO-TETA could be explained for acid–base interaction and hydrogen bonding interaction.     

Structure effect of some amine derivatives on corrosion inhibition efficiency for carbon steel in acidic media using electrochemical and Quantum Theory Methods

The structure effect on corrosion inhibition of two amines and their derivatives is the main object of this article. The first amine was 1,8-diaminooctane and its ethoxylated (50 e.o.) 1,8-diaminooctane and propoxylated (50 p.o.) 1,8-diaminooctane. The second amine is the tetraethylenepentamine and its ethoxylated (50 e.o.) and propoxylated (50 p.o.) derivatives. The investigations were carried out by open circuit potential, potentiodynamic polarization, electrochemical impedance, quantum calculations and SEM measurements. The data obtained for the first amine showed the minimum inhibition efficiency (65.5%), meanwhile the maximum inhibition efficiency was 78.9% for its propoxylated derivative. On the other hand the maximium inhibition efficiency was 91% for the second propoxylated amine. The electronic properties; HOMO and LUMO energy levels, energy gap, dipole moment, polarizability, log P, total energy, charge densities, area/molecule and hydration energy have been calculated. The inhibition efficiency was calculated theoretically using the electronic parameters. From the obtained results, there is a significant difference between the inhibition efficiency of the electronic and the inhibition efficiency experimentally. The results were discussed on the light of the chemical structure of the used inhibitors. In general, the inhibition efficiency is affected by the shape and structure of the molecule.     

An FPGA implementation of a neural optimization of block truncation coding for image/video compression

This paper presents a Field Programmable Gate Array (FPGA) implementation for image/video compression using an improved block truncation coding (BTC) image compression technique. The improvement is achieved by employing a Hopfield neural network (HNN) to calculate a cost function upon which a block is classified as either a high- or a low-detail block. Accordingly, different blocks are coded with different bit rates and thus resulting in better compression ratios. The paper formulates the utilization of HNN within the BTC algorithm in such a way that a viable FPGA implementation is produced. The implementation exploits the inherent parallelism of the BTC/HNN algorithm to provide efficient algorithm-to-architecture mapping. The Xilinx VirtexE BTC implementation has shown to provide a processing speed of about 1.113 × 10⁶ of pixels per second with a compression ratio which varies between 1.25 and 2 bits/pixel, according to the image nature.     

Narratives of Spatial Division： The Role of Social Memory in Shaping Urban Space in Belfast

The paper examines the role of shared spaces in divided cities in promoting future sustainable communities and spaces described as inclusive to all. It addresses the current challenges that prevent such inclusiveness and suggests future trends of its development to be of benefit to the wider city community. It explains how spaces in divided cities are carved up into perceived ownerships and territorialized areas, which increases tension on the shared space between territories; the control of which can often lead to inter-community disputes. The paper reports that common shared space in-between conflicting communities takes on increased importance since the nature of the conflict places emphasis on communities＇ confidence, politically and socially, while also highlighting the necessity for confidence in inclusion and feeling secure in the public domain. In order to achieve sustainable environments, strategies to promote shared spaces require further focus on the significance of everyday dynamics as essential aspects for future integration and conflict resolution.     

Performance analysis of spread spectrum packet radio network withchannel load sensing

A continuous-time Markov-chain model for an asynchronous communication spread-spectrum code-division-multiple-access (CDMA) packet radio network is developed. The network is composed of mutually independent users. The receiver-based code is considered; a terminal with a packet to send looks up the destination's code and transmits on that code. Each user senses the channel load and refrains from transmission if the channel load exceeds the channel threshold. The model makes it possible to study the threshold effect of channel load on the performance of the CDMA packet radio network. Improvements in performance of spread-spectrum packet radio networks due to channel-load sensing are shown. Steady-state results for throughput are obtained     

Adsorption Behavior of Co(II) and Eu(III) on Polyacrylamide/Multiwalled Carbon Nanotube Composites

Multiwalled carbon nanotubes were used for the synthesis of five different polyacrylamide/ MWCNT composites. Different polymerization techniques were applied, namely, copolymerization, template polymerization of monomers on polyacrylamide, or grafting method, all induced by γ-irradiation. Fourier transform IR spectra were used for characterization. These composites were used for studying the adsorption and separation behaviors of Co(II) and Eu(III) under various experimental conditions. Radioactive isotopes ⁶⁰Co and ^152+154Eu were used for tracing the corresponding elements. The adsorption on the related polymers was also studied for comparison. The K_d values for the adsorption on the nanocomposites were found to be much higher than those on the corresponding polymers. Complete adsorption was achieved on some of the synthesized nanocomposites under definite conditions, suggesting the possibility of complete isolation of Co(II) and/or Eu(III) from large volumes of aqueous solutions. Separation of Co(II) and Eu(III) from each other was also found to be possible under certain conditions.

     

A closed slot-line resonator filter

A microwave bandpass filter made from three-dimensional (3-D) slot-line resonators is described. This structure readily lent itself to the design and realization of a 16-pole filter. By concentrating the losses on the resonant element, very high Q can be achieved by using low surface resistance material, such as high temperature superconductor, for the slot-line resonator. The filter is five to ten times smaller than previous generation 3-D filters made using high temperature superconductors.     

Failure of a Vertical Drainage System Installed to Fight the Rise of Groundwater in El-Oued Valley (SE Algeria): Causes and Proposed Solutions

El-Oued Valley suffers from the problem of rising groundwater which affects agricultural and urban areas and degrades all aspects of the socioeconomic life of its inhabitants. This problem, which appeared in the 1980s, is primarily a result of overexploitation of deep groundwater, lack of sanitation network, and discharge of wastewater directly into the unconfined aquifer. To solve this problem, a megaproject was carried out, based on the principle of sewerage, to drain and evacuate excess water after treatment to a discharge site 70 km north of the region. In this project, the blade of groundwater above elevation of 60 m should be drained through wells of a vertical drainage system. However, the expected results have not been achieved in most affected cities, where the groundwater level continues to rise. Herein, we propose a solution to this problem, based on a new explanation of the hydrogeological structure of the unconfined aquifer that drives the rising groundwater to the surface. The main part of this research is based on interpretation of well tests carried out in wells of the vertical drainage system.     

Thermal effects on GFRP rebars: experimental study and analytical analysis

The bond mechanism between Glass Fiber Reinforced Polymer (GFRP) bars and concrete is investigated through experimental testing and analytical modeling. This bond depends on several parameters such as temperature. The present paper studies the thermal effect, under high temperature up to 80°C, on bond behaviour at the interface GFRP bars/concrete through pullout-testing. These tests are conducted on specimens after 24 h of exposure at various temperatures. The thermal effect on an average short-term bond strengths and the pullout-load versus end-slip behaviours are compared to untreated specimens (20°C). Some pullout-tests on steel bars/concrete are also performed for the comparison. Experimental results show no significant change in the average bond strength for specimens subjected to temperatures up to +60°C. On the other hand at 80°C, there is a decrease of bond strength of about 22 and 28% for the 8 mm and the 16 mm diameter rods, respectively. An analytical model of the bond stress-slip response of a GFRP/concrete bar has been proposed. The results show good accuracy between the model and the experimental results.