Removal of Congo Red dye by adsorption onto phyrophyllite

Synthetic dye‐containing wastewaters from textile, paper, plastic and leather‐tanning industries are a most common organic pollutant. Such dyes may be toxic not only to aquatic life, but also to human beings. Consequently, dye removal from wastewater significantly benefits the environment. The aim of this study was to investigate the effectiveness of phyrophyllite as an adsorbent for Congo Red dye from wastewater. Dye sorption rates were investigated in bench‐scale studies. Evaluation of adsorption performance of phyrophyllite on Congo Red necessitated the determination of Langmuir and Freundlich isotherms. Adsorption of Congo Red on phyrophyllite was found to be in conformity with both isotherms. The adsorption capacity for phyrophyllite was found to increase with decrease in particle size and with increase in temperature and intensity of agitation. The results indicated that phyrophyllite was a good adsorbent for Congo Red from wastewaters.     

Physical mechanism of solvolytic liquefaction of coal through depolymerization: Factors leading to reduction in reagent concentration and reaction time

This Paper reports studies on the depolymerization reaction of Assam coal using p-toluenesulphonic acid (PTS) in phenol. Attempts have been made to determine the true extractability of coal by depolymerization by balancing the mineral matter present in the original coal with that in the residual depolymerized coal after extraction, and thus allow for the addition of phenol to the coal. The factors that could lead to a reduction in the amount of catalyst and reaction time required for depolymerization were studied. Three successive depolymerization reactions, followed by extractions in benzene/methanol (7:3 vol/vol), allowed the extraction of ≈50% coal with a coal:catalyst (PTS) ratio of 2:1. The particle size of the coal also affected the depolymerization reaction. Smaller coal particles (? 60 to + 120 BSS mesh, 250-125 gmm) resulted in a better extraction (60% in benzene/methanol (7:3 vol/vol)) compared with larger particles. The depolymerization reaction was found to be under diffusion and chemical control within the coal particle. Exposure of active sites in coal through extraction, increase in surface area through size reduction, chemical pretreatments, use of promoters and elevated temperatures should help to increase the rate of the depolymerization reaction.     

Role of mineral matter in the chemical reactivity of coal

Previous work showed that the solvent extraction yield of coal increased as a result of chemical reactions such as formylation, reductive acylation, acylation, amidomethylation, alkylation, reduction and depolymerization. In the work described in this Paper, dmmf coal obtained after demineralization with mixed HF-HCI acids was used for solvolytic extraction studies after depolymerization, alkylation, acylation, amidomethylation, reductive acylation and reduction reactions. In comparison with the original coal, mineral matter free coal showed less increase in extractability as a result of these reactions indicating that mineral matter present in the original coal was acting as a promoter for these reactions.     

Enhancement of benzene-methanol extraction (low molecular weight products) of coal in depolymerization reactions

Depolymerization of coals is an important reaction for the study of coal structure. Coal is depolymerized by using p-toluenesulphonic acid in phenol. Depolymerization takes place mainly through the cleavage of C-C and C = bonds and subsequent phenolation, whereas C-O-C linkages of coal are not affected by this treatment. In the present work, reactions, such as, reduction of coal through Li in ethylene-diamine, alkaline-degradation and dry HCl gas, which are known to cleave C-O-C linkages in coal selectively, have been coupled (as a pre-treatment) with depolymerization reactions. This could enhance the yields of low molecular weight products from coal as revealed by the enhancement in the benzene-methanol (7/3 vol/vol) extractability of depolymerized coals. The use of Ce(IV) salt, benzoyl peroxide, lead tetra-acetate and potassium persulphate, promotes the depolymerization reaction to low molecular weight products. These studies help in understanding the mechanism of generation of asphaltenes and, thereby, might help in the studies of liquefaction of coal.     

Provable Cryptographic Security and its Applications to Mobile Wireless Computing

Many attempts to secure mobile wireless systems have failed abysmally. Notable examples include 802.11 WEP, as well as major cellular phone standards such as TDMA, CDMA, and GSM. The attacks typically result from the correct use of a bad cryptographic primitive or the incorrect use of a good one. By designing provably secure algorithms and protocols, we not only minimize the time required to gain confidence in the security of a system, but we virtually eliminate the possibility of a cryptographic vulnerability. Unfortunately, the concept of “provable securit” is often misunderstood. In this survey paper, we state precisely what provable security is and is not, and describe the benefits of the approach.     

Solvolytic extraction of coal through acylation and amidomethylation

Carboxylic acids, acid anhydrides and N-hydroxy methylamides were used to acylate Assam coal under Friedel—Crafts reaction conditions. This reaction resulted in the enhancement of the extractability of coal in benzene—methanol (7:3 vol./vol.) and quinoline after acylation with carboxylic acids and acid anhydrides. The effect of catalyst (AlCl₃) concentration on reaction was also investigated. l.r. spectra of reaction products indicated the introduction of acyl groups in the coal structure. Phthalimidomethylation could render about 50% coal extractable in quinoline.     

The removal of nickel,copper and cadmium from aqueous solution using liver moss (Dumortiera hirsute Sw. nees)

The aim of this study was to investigate the use of liver moss (Dumortiera hirsute Sw. nees) as an alternative adsorbent for the removal of nickel, copper and cadmium from aqueous solution. The results showed that equilibrium contact time was 60?min and acidic pH was favourable for removal of metal ions. Higher initial metal ion concentrations led to lower removal. The data were fitted well both Langmuir and Freundlich isotherms. The monolayer adsorption capacities were 30.675, 35.971 and 53.476?mg/g for nickel, copper and cadmium, respectively. The presence of metal ions such as sodium, potassium and magnesium at concentration of 10?mM was found to have no significant effect on the removal of nickel, copper and cadmium. The removal of nickel, copper and cadmium was markedly inhibited, however, in the presence of calcium ion and heavy metal ions mixture in solutions. The kinetic data for removal processes were described by the pseudo-second-order model. The liver moss shows high potential as an economic and abundant material for the removal of metal ions from aqueous solution.     

Fe3O4 nano-particles prepared by co-precipitation method using local sands as a raw material and their application for humic acid removal

Magnetic Fe₃O₄ nano-particles were prepared successfully from commonplace sands as a raw material. The nano-particles were synthesized by chemical co-precipitation of high purity iron separated from commonplace sands through acidic leaching. The characterization of the synthesized nano-particles was performed using X-ray diffraction, fourier transform infrared, scanning electron microscopy, transmission electron microscopy, and potential zeta. Finally, the nano-particles were used for adsorption of humic acid (HA) from aqueous solutions using batch adsorption technique. The effects of pH, adsorbent dosage, agitation time, initial HA concentration, and temperatures on HA adsorption were evaluated. The adsorption of HA onto nano-particles followed the Sips isotherm and pseudo-second order kinetics models. Thermodynamic parameters data indicated that the HA adsorption process was non-spontaneous and endothermic under the experimental conditions. The adsorption of HA from peat water (the real sample) using the nano-particles demonstrated that they were an adsorbent with great potential for the removal of HA from peat water.