Sorption

The classic Langmuir and Freundlich sorption models and a dual-mode approach have been tested to study the sorption of aromatic molecules onto β-cyclodextrin polymers as well as onto analogous sucrose polymers, obtained using the same crosslinking agents (epichlorohydrin, succinyl chloride, toluene diisocyanate, and hexamethylene diisocyanate). The host–guest interaction of the sorbate within the cyclodextrin cavities corresponds to the hole-filling mechanism

The equilibrium, kinetics, and thermodynamics of the biosorption of Pb(II), Cd(II) and Zn(II) onto groundnut (Arachis hypogaea) shell were investigated under various physicochemical parameters. Optimisation studies were carried out using batch biosorption studies. The extent of the metal ion biosorption increased with increase in solution pH, initial metal ion concentration, dosage of biosorbent and contact time but decreased with the temperature of the system. The biosorption of each of the metal ions was found to be pH-dependent. Kinetic study showed that the metal ions biosorption process followed the pseudo-second-order kinetic model. The sorption of each metal ion was analysed with Freundlich and Langmuir isotherm models, in each case, the equilibrium data were better represented by Freundlich isotherm model. Thermodynamically, parameters such as standard Gibbs free energy (ΔG˚), standard enthalpy (ΔH˚), standard entropy (ΔS˚) and the activation energy (A) were calculated. The ...

Reduction of water activity aw can extend the shelf life and improve the quality of foods. After the optimal water activity has been selected, based on Karel’s aw-spoilage graphs, a simple decision scheme in this document helps to choose the best equation (“Law”) to calculate or adjust the water activity: for an aqueous one component  solution: Raoult’s and Norrish’ laws; spreadsheet “aw-Raoult-Norrish.xls”; or in case of an aqueous multi-component solution: Norrish’ and Ross’ laws; spreadsheet “Norrish-Ross.xls: aw calculations of a multi-component solution”. Both Excel spreadsheets, present in this document, simplify the tedious exponential aw calculations.
The water activity of a mixture of 2 to 5 solids can be predicted either by constructing the solids mixture sorption isotherm, or by using the Salwin equation. When applying the 3rd spreadsheet in this document, “Calculation Water Activity aw Solids Mixture.xls”, the  2 to 5 separate solids isotherms are converted into one new solids mixture sorption isotherm. Because the total water content of the solids mixture is known, the water activity of the solids mixture can be found from that new mixture isotherm. The calculations by the “aw Solid Mixture” spreadsheet are compared with aw findings from Salwin’s equation. Both aw values are in good agreement.
Several worked examples, for each of the 3 spreadsheets present, illustrate step-by-step the aw calculation of solutions and of solid mixtures.
Annex 1 lists the lowest water activity for growth and/or toxin production of many micro-
organisms in foods. Annex 2 shows the minimal aw for activity of the main food spoiling enzymes.

Molecularly imprinted polymers (MIPs) are tailor-made polymers with high selectivity for a given analyte, or group of structurally related compounds. The influence of the process parameters (the moles of functional monomer and cross-linker, the selection of functional monomer and solvent) on the preparation of oseltamivir (OS)-imprinted polymers was investigated. A mathematical method for uniform design to optimize these selected parameters and to increase the MIP selectivity for template molecules was applied. The optimal conditions to synthesize MIP were 0.69 mmol 30% acrylamide (AA) + 70% 4-Vinylpyridine (4-VP) and 5.0 mmol ethylene glycol dimethacrylate (EGDMA) copolymerized in 5 ml toluene in the presence of 0.1 mmol OS. MIP showed high affinity and selectivity for separation of the template molecule from other compounds. In the present study, we have established an effective LC-MS/MS method to identify and quantify OS with good sensitivity, accuracy and precision. Figure A Complexation; B polymerization and template removal; C MIP has high affinity to template molecule; D MIP has some affinity to template molecule analog; E MIP has no affinity to other chemicals with different type from template molecule. a Template molecule; b template molecule analog; c other chemicals

Reduction of water activity aW can improve the shelf life and the quality of foods. After
selecting the optimal water activity, a simple decision scheme helps to choose the best
equation (“Law”) to calculate or adjust the water activity: of an aqueous one component
solution (Raoult’s and Norrish’ laws), or of an aqueous multi-component solution (Norrish’ and Ross’ laws). For aqueous solutions of sugars, salts, electrolytes, and salt or fat replacers, three spreadsheets simplify the tedious exponential aW calculations: 
"aW-Raoult-Norrish.xlsx", and "aW-Pitzer equations.xlsx", for one component aqueous
solutions; spreadsheet "Norrish, Ross, Samapundo, Pitzer, and Baeza.xlxs" for
multi-component aqueous solutions. Sometimes, for a particular component, 2 or 3 aW equations are available; if possible, the equation’s  accuracy will then be reported.
The water activity of a mixture of 2 to 5 SOLIDS can be predicted either by constructing the solids mixture sorption isotherm, or by using the Salwin equation. When applying the
spreadsheet "Calculation Water Activity aW Solids Mixture.xlsx", the separate solids
isotherms are converted into one new solids mixture sorption isotherm. Because the total water content of the solids mixture is known, the water activity of the solids mixture can be found from that new mixture isotherm. Calculations with the "Solid Mixture" spreadsheet are validated by comparing its predicted solids mixture aW with the water activity, calculated by the Salwin equation. The two calculated solid mixture aW values are in good agreement.
Annex 1 lists the lowest water activity for growth and/or toxin production of many micro-
organisms in foods. Annex 2 shows the lowest aW for activity of the main food spoiling enzymes. Annex 3 gives many sources of Norrish k values; Annex 4 reports measured water activities for verification.
Several worked examples for each of the spreadsheets illustrate step-by-step the
aW calculation of aqueous solutions and of solid mixtures.

The  problem  of environmental  pollution  is  more expressed and more present by the development of the industry and  the  growth  of  the  human  population.  Pollution  of  natural and wastewater is most often due to the release of heavy metals into  watercourses.  The  greatest  challenge  for  researchers  is choosing  the  right  biomass  from  a  large  number  of  low-cost biomaterials,  and  availability  and  price  are  very  important selection  factors.  Microbial  biomass,  forestry  waste  and agroindustrial complexes are most frequently examined, as well as  various  macromolecules  of  natural  origin.  In  this  paper, barley straw that arises as agricultural waste product in barley production  in  Bosnia  and  Herzegovina,  was  used  as  a biosorbent. In  the  experimental  part,  physical  and  chemical characterization  of    barley  straw  was  performed,  after  which the  efficiency  of  removing  Cd(II)  and  Ni(II)  from  aqueous solutions,  using  barley  straw,  and  the  influence  of  process parameters  (pH  value  of  aqueous  solution,  biosorbent  size, interaction  of  metal  ions)  on the  biosorption  capacity  were tested.It can be concluded that barley straw has good adsoption characteristics  for  the  use  as  a  low-cost  natural  sorbent  for  the removal of heavy metals from water.