a b s t r a c tCorn cobs were evaluated as raw material in the production of an adsorbent for phenylalanine removal from aqueous solutions. Batch adsorption studies were conducted at 25, 35 and 45 C, respectively. Adsorption equilibrium was attained after 3 h and Langmuir, Freundlich, Temkin, and Langmuir eFreundlich models were tested for equilibrium description, with LangmuireFreundlich providing the best fits. Adsorption kinetics was better described by a pseudo-second-order model. The predominant adsorption mechanism was verified to be of the p-p type of interaction between the aromatic ring of phenylalanine molecule and the graphene rings at the carbon surface. Other mechanisms were also observed. The maximum value of uptake capacity, 109 mg g À1 , was similar or higher than values encountered in the literature for other types of adsorbents.

Defective coffee press cake, a residue from coffee oil biodiesel production, was evaluated as an adsorbent for removal of basic dyes (methylene blue--MB) from aqueous solutions. The adsorbent was prepared by microwave treatment, providing a significant reduction in processing time coupled to an increase in adsorption capacity in comparison to conventional carbonization in a muffle furnace. Batch adsorption tests were performed at 25 degrees C and the effects of particle size, contact time, adsorbent dosage and initial solution pH were investigated. Adsorption kinetics was better described by a second-order model. The experimental adsorption equilibrium data were fitted to Langmuir, Freundlich and Tempkin adsorption models, with Langmuir providing the best fit. The results presented in this study show that microwave activation presents great potential as an alternative method in the production of adsorbents.

Adsorption of phenolic amino acids, such as phenylalanine and tyrosine, is quite relevant for the production of protein hydrolysates used as dietary formulations for patients suffering from congenital disorders of amino acid metabolism, such as phenylketonuria. In this study, an adsorbent prepared from corn cobs was evaluated for the removal of tyrosine (Tyr) from both a single component solution and a binary aqueous solution with phenylalanine (Phe). The adsorption behavior of tyrosine was similar to that of phenylalanine in single component solutions, however, with a much lower adsorption capacity (14 mg g−1 for Tyr compared to 109 mg g−1 for Phe). Tyr adsorption kinetics was satisfactorily described by a pseudosecond-order model as it was for Phe. In adsorption equilibrium studies for binary mixtures, the presence of Tyr in Phe solutions favored Phe faster adsorption whereas the opposite behavior was observed for the presence of Phe in Tyr solutions. Such results indicate that, in binary systems, Phe will be adsorbed preferably to Tyr, and this is a welcome feature when employing the prepared adsorbent for the removal of Phe from protein hydrolysates to be used in dietary formulations for phenylketonuria treatment.

This paper presents a comparative evaluation of three lignocellulosic residues (corn cobs, spent coffee grounds and Raphanus sativus press cake) as precursor materials in the production of activated carbons (ACs). Results indicate that the precursor material has a significant effect in both physical and chemical aspects of the adsorbent as well as on the adsorption mechanisms. Highest and lowest values of iodine number and density were observed for ACs based on press cake and corn cobs, respectively. Regardless of the observed differences in surface chemical make-up and adsorption mechanisms, all employed materials were deemed adequate for adsorbent production, since the prepared ACs presented adsorption capacities similar or even higher than those of commercial ACs and other residue-based adsorbents.

This paper presents a comparative evaluation of three lignocellulosic residues (coffee husks, spent coffee grounds and pequi husks) as precursor materials in the production of activated carbons (ACs). Results indicate that the precursor material has a significant effect in both physical and chemical aspects of the adsorbent, with the AC based on spent coffee grounds being the most effective for phenol removal, with maximum adsorption capacity comparable to commercial ACs.

This study evaluates the potential of Crambe abyssinica press cake, a residue from crambe oil extraction and/or biodiesel production, as an adsorbent for removal of cationic dyes from wastewaters. Batch adsorption tests were performed at 30, 40 and 50 o C. Adsorption kinetics and equilibrium were satisfactorily described by the pseudo second-order and Freundlich models, respectively. Adsorption was spontaneous and exothermic. Fixed bed adsorption (breakthrough curve) was satisfactorily described by the Dose-Response model. The obtained values of maximum adsorption capacity were 79.7 and 102.5 mg g-1 in batch and continuous systems, respectively. Adsorption tests showed that crambe press cake, without any thermal treatment, presented higher adsorption capacity than activated carbons produced from other oilseed press cakes (sunflower, coffee and Raphanus sativus), confirming that this type of waste material is a suitable candidate for use in the production of adsorbents.

Abstract-Agricultural residues were evaluated as raw material in the production of adsorbents for phenol removal from aqueous solutions. A comparative evaluation of acid and basic activating agents is presented. Adsorption kinetics and equilibrium were satisfactorily described by the pseudo second-order and Freundlich models, respectively. Adsorption tests showed that the prepared adsorbents presented higher adsorption capacity than activated carbons produced from other agricultural residues, confirming that this type of waste material is a suitable candidate for use in the production of adsorbents.

Hydrocolloids of Pereskia aculeata Miller (DPNH) are potential ingredients in food industry as emulsifiers and stabilizers. The extraction process of DPNH requires the removal of pigments with activated carbon. Because this step is critical to the quality of the ingredient and has an impact on costs, a new activated carbon has been developed with residues from the same process. Residues activated with NaDH and H 3 PD 4 (300 °C, 1 h) were subjected to batch adsorption tests in model solutions of malachite green (MG), carbohydrate and protein. Residue treated with 85% H 3 PD 4 (DPNAC) had higher productivity and MG adsorption capacity, displaying a predominantly microporous surface (MEV/BET) with chemical activation confirmed by TG/FTOR. DPNAC showed higher MG and protein adsorption capacity than the commercial activated carbon (CAC) did. Results for MG-adsorption capacity by DPNAC did not show significant differences in the presence of protein and carbohydrate, presenting the higher affinity of the adsorbent for the dye. Adsorption isotherms showed DPNAC to be more favorable to MG adsorption than CAC, and to have a good fit to Langmuir-Freundlich model. DPNAC made it possible to reduce costs and allowed the sustainability of the process, leading to increased efficiency in selective pigment removal compared with CAC.Keywords: adsorption; carbohydrate; malachite green; protein; sustainable process.Practical Application: The activated carbon obtained using solid residues of the extraction process of hydrocolloids from Pereskia aculeata Miller proved to be more effective in protein and pigment adsorptions and less effective in carbohydrate adsorption when compared to using a commercial activated carbon. The potential use is waste treatment systems and clarification process.