Functionalisation of cross-linked polyethylenimine for the removal of As from mining wastewater

Cross-linked polyethylenimine (CPEI) was phosphonated by reaction with phosphorous acid and formaldehyde. The functionalised polymer was used as an adsorbent for the removal of arsenic as an oxo-anion. The binding affinity of the synthesised polymer to abstract As from synthetic solutions and wastewater samples was assessed, as well as its ability to be regenerated for re-use. The PCPEI demonstrated an elevated loading capacity, removing up to 88% of As. The kinetic rates were modelled using pseudo first-order and pseudo second-order equations. The pseudo second-order equation was found to explain the adsorption kinetics most effectively, implying chemisorption. The Langmuir and Freundlich isotherms were used to interpret the adsorption of As onto PCPEI. The Freundlich isotherm was found to best fit and describe the experimental data. The thermodynamic study of the adsorption process indicated high activation energies (55.91 kJ mol-1) which confirms chemisorption as a mechanism of interaction between As and PCPEI.Keywords: Adsorption; arsenic; phosphonated cross-linked polyethylenimine, functionalisatio

Kinetic, equilibrium and thermodynamic modelling of the sorption of metals from aqueous solution by a silica polyamine composite

Batch sorption studies were conducted to assess the potential of a phosphonated silica polyamine composite (BPAP) to remove metals (Co, Cu, Fe, Mg, Mn, Ni, U and Zn) from mine waters. The metal adsorption showed a good Langmuir isotherm fit. Ni and Mn fitted both the Freundlich and Langmuir isotherms. The activation energies (Ea) of Co, Mg and Ni ranged between 5 and 40 kJ∙moℓ-1, signifying physisorption while U showed a chemisorption type of adsorption (with Ea > 50 kJ∙moℓ-1). Cu and Fe on the other hand gave negative Ea values, indicating their preference to bind to low-energy sites. The pseudo-second-order kinetic model provided the best correlation of the experimental data, except for Mg and Ni for which the pseudo-first-order model and the Elovich model gave a better fit, respectively. Adsorption was almost constant over a wide pH regime and increased with time. Adsorption increased with concentration of the metals with the exception of Co, Fe and Ni which displayed about a 40% drop at a concentration of 200 mg∙ℓ-1. Desorption experimental data gave poor results except for U which showed 99.9% desorption.Keywords: silica polyamine composite, sorption, kinetics, isotherms, desorptio

Health Hazards Associated with Wheat and Gluten Consumption in Susceptible Individuals and Status of Research on Dietary Therapies

Wheat accounts for about 20% to over 50% of the total calorie intake of food in regions where it is grown. However, there is a clear perception that disorders related to the consumption wheat are increasing, particularly in Western Europe, North America, and Australia. We consider here the evidence for this perception and discuss strategies and therapies that may be used to reduce the adverse impacts of wheat on the health of susceptible individuals. First, we will introduce the major groups of wheat grain proteins, focusing on those associated with adverse reactions, and discuss in detail the three major adverse reactions triggered by wheat consumption, namely celiac disease, wheat allergy, and non-celiac gluten/wheat sensitivity. Finally, will discuss other issues associated with the consumption of gluten-free foods focusing on gluten contamination of products purported to be gluten-free, gluten threshold or tolerance among celiac patients, and food labeling