Phosphorus recovery from sewage sludge – phosphorus leaching behavior from aluminum-containing tertiary and anaerobically digested sludge

Systematic investigations of the acidic dissolution of phosphorus (P), aluminum (Al), iron (Fe), and calcium (Ca) from Al-containing tertiary sludge were carried out in this work. The results were compared with the dissolution behavior of Al-containing anaerobically digested sludge to evaluate the P recovery potential in the form of struvite from tertiary sludge versus anaerobically digested sludge. Additional investigations of synthetically produced Al sludge served as a comparison for the dissolution behavior of P and Al without the influence of other contaminants (metals, biomass). In addition, the acid consumption was analyzed as a function of the target pH during the dissolution. The dissolution efficiency of ortho-phosphate in tertiary and anaerobically digested sludge after acid treatment at pH 2 was ∼90%. The dissolution efficiency of Al and Ca in tertiary sludge was also ∼90% at pH 2, while the release efficiency of Al and Ca in anaerobically digested sludge was lower, ∼70% at pH 2. In tertiary sludge, about 75% of Fe was found dissolved at pH 2, whereas in anaerobically digested sludge this value was higher, ∼90%. Based on the experimental data, it can be concluded that significant dissolution of phosphorus from Al-containing tertiary sludge can take place at pH < 3. The highest sulfuric acid consumption for P dissolution was observed in the case of tertiary sludge at pH 2.

Carboxymethylation of Karaya gum: application in gastroretentive drug delivery for sustained release of model drug

Karaya gum (KG) is one of the least soluble of the gums. It does not dissolve in water to give a clear solution but instead absorbs water rapidly to form viscous colloidal sols. Carboxymethylation of Karaya gum is expected to improve its aqueous solubility and gelling behavior. Another objective of the research is to evaluate the potential of carboxymethylated Karaya gum (CMKG) as drug release modulator (in acidic dissolution medium) when combined with HPMC K15M based polymeric matrices bearing Propranolol HCl. In the present study, KG was carboxymethylated using Williamson Ether synthesis. FTIR spectroscopy confirmed the formation of CMKG. The prepared CMKG was used in conjunction with HPMC K15M as a polymer matrix in the formulation capsule dosage form, using Propranolol HCl as model drug. The filled capsules were then coated with Gelucire 43/01 to convert them into hydrodynamically balanced (HBS) capsule dosage form. Dextrose & fructose were also added to the drug-polymer mix as osmogen to facilitate the drug release. The degree of substitution of CMKG was found to be 0.87. HBS capsule dosage forms remained buoyant on 0.1 HCl for up to 6 hr, the buoyancy was attributed to the Gelucire 43/01 coating around the capsule shell. From the experimentation it was observed that CMKG, when mixed with HPMC K15M at 1:3 ratios, extended the release of model drug from HBS capsule dosage forms in 0.1 HCl. At CMKG: HPMC K15M ratio 2:1, release of Propranolol Hydrochloride from hydrodynamically balanced (HBS) capsules revealed fast drug release in 0.1 HCl. From the observations it is evident that KG is amenable to carboxymethylation to form CMKG. It is also evident that it is advantageous to combine CMKG with HPMC K15M as release modulator to retard the release of Propranolol HCl in acidic dissolution medium.

Preparation and In-vitro Characterization of Gastroretentive Floating Tablets of Domperidone

The present investigation was design for domperidone floating table preparation and in-vitro characterization. The ultimate target was increasing gastric retention by means of floatability of the tablet. Hydrophilic cellulosic polymers, Methocel K15M and Methocel K100M were used in this experiment for achieving release controlling property. Sodium bicarbonate played the key role of floatation by generating gas. Direct compression was the method of choice for preparing the tablets. The tablets were evaluated for physical parameters, buoyancy study, total floating time determination and dissolution study. Acidic dissolution medium (0.1N HCl), mimicking the environment of the stomach, was used in USP II apparatus for 12 hours to find out the pattern of drug release. The release mechanism was analyzed by exploring the zero order, first order, Higuchi and Korsmeyer equations. All the physical parameters were within acceptable range and Methocel K100M showed more floating lag time and sustained release property than Methocel K15M. All the formulations showed more than 12 hours floating time. Fourier Transform Infrared Spectroscopy (FTIR) study confirmed the compatibility of the drug with the excipients. Bangladesh Pharmaceutical Journal 22(2): 170-175, 2019

COPPER AND LEAD RECOVERY FROM DISCARDED PRINTED CIRCUIT BOARDS BY ELECTROLYSING LEACHED SOLUTION

Results of copper and lead recovery from discarded printing circuit boards (PCB) by acidic dissolution and electrodeposition are presented. A preliminary procedure of the recovery process is proposed with the following steps: disposal of the mounted electrical elements, cleaning, grinding, iron separation for grains screening, metal dissolution, and electrolysis. The composition analysis is performed to define suitable electrochemical parameters for recovery. XRF and AAS techniques are used for preliminary estimation of metal content in leached solution. LSV method is implemented to establish parameters for copper electrodeposition. The product quality is evaluated through XRD analysis. The high recovery efficiencies, 97.61% and 96.59 % for copper (in metallic form) and lead (in dioxide form), respectively, were reached.

Bioelectrochemical Changes During the Early Stages of Chalcopyrite Interaction with Acidithiobacillus thiooxidans and Leptospirillum sp.

A bioelectrochemical study of charge transfer in the biofilm/chalcopyrite interface was performed to investigate the effect of surficial sulfur reduced species (SRS), as non-stochiometric compounds or polysulfides (Sn2-), and elemental sulfur (S0) on a biofilm structure during the earliest stages (1, 12 and 24 h) of chalcopyrite biooxidation by A. thiooxidans alone and adding Leptospirillum sp. The surface of massive chalcopyrite electrodes was exposed to the bacteria, which were analyzed electrochemically, spectroscopically, and microscopically. At the studied earlier times, charge transfer and significant differences in the biofilm structure were detected, depending on the presence of Leptospirillum sp. acting on A. thiooxidans biofilms. Such differences were a consequence of a continuous chalcopyrite pitting and promoting changes in biofilm hydropathy. A. thiooxidans modifies the reactive properties of SRS and favors an acidic dissolution, which shifts into ferric when Leptospirillum sp. is present. A. thiooxidans allows H+ and Fe3+ diffusion, and Leptospirillum sp. allows surpassing the charge transfer (reactivity) barrier between the mineral interface and the ions. The observed changes of hydropathy on the interface are associated to ions and electrons activity and transfer. Finally, a model of S0 biooxidation by A. thiooxidans alone or with Leptospirillum sp., is proposed.