Effect of solution pH and influence of water hardness on caffeine adsorption onto activated carbons

Abstract

There has been little research into the effects of the water hardness and pH of surface waters on the adsorption of caffeine on activated carbons. The aim of this study was to determine the influence of these water characteristics on different activated carbons. Caffeine adsorption from the aqueous phase was studied using biomass derived activated carbons (DD: dende coco and BB: babassu coco) and a commercially available activate carbon (NO: Norit® GAC 1240 plus). The functionalized carbons in an inert atmosphere was also studied and were denominated DI, BI, NI. Results highlight the importance of pH in caffeine adsorption: the highest removals were obtained for pH 3.0 and decrease for higher pH. The adsorption isotherms obtained were fitted to the Freundlich and Langmuir models. Calcium and magnesium ions were adsorbed to a varied extent on the activated carbons. The hardness in solution decreased their adsorption due to a competition effect. KF and qm from the Freundlich equation linearly decreased with water hardness due to salt‐screened electrostatic repulsions between charged molecules. The amount adsorbed from deionized water was largest because there was no competition between inorganic ions and molecules.

Synthesis of activated carbon from peanut shell as dye adsorbents for wastewater treatment

“…All types of biological wastes, such as palm shell (Lim et al, 2015), peanut shell (Malik et al, 2007), coconut shell (Couto et al, 2015), castor shell (Thamilarasu and Karunakaran, 2013) and coffee residue (Lamine et al, 2014), can be used as low-cost precursors for the preparation of activated carbon. China is the world's largest peanut producer.…”

Effect of Solution pH on the Removal of Paracetamol by Activated Carbon of Dende Coconut Mesocarp

“…At pH 11, paracetamol molecule was repealed by the negatively charged carbon surface 26,27 . At pH PZC and pH 2, the neutral paracetamol molecules were adsorbed by the equally neutral and positively charged adsorbent surface.…”

“…The amount of pharmaceutical compounds adsorbed onto activated carbon is usually directly proportional to the micropore volume 6,26,27 . Therefore, the promising results obtained at pH 6.5 and 2 may be a consequence of the significant contribution of the predominant microporous adsorbent and its surface charge.…”

Physicochemical Conditions for Adsorption of Lead from Water by Rice Husk Ash

“…Adsorption isotherms provide insight into the sorption mechanisms, surface properties, and affinity of adsorbent (Khan et al 2009). The Langmuir isotherm better describes monolayer adsorption, which assumes that the adsorbent surface is energetically homogeneous and that a monolayer surface coverage is formed with no interaction between the molecules adsorbed (Couto et al 2015). The Freundlich isotherm recognizes the possibility of surface heterogeneity and intermolecular interactions between adsorbed molecules.…”

“…This also affects the surface charge on the adsorbent and the degree of ionization and speciation of the adsorbent. The solution pH determines both the predominant species and the net charge on the surface of the adsorbent (Couto et al 2015). Higher adsorption efficiencies were recorded at low pH.…”