Adsorptive separation of heavy metals from an aquatic environment using orange waste

Adsorptive Removal of Trace Concentration of Fluoride Using Orange Waste Treated Using Concentrated Sulfuric Acid

“…Figure 5 shows the% adsorption of Zr(IV) onto ATOJR at varying pH at equilibrium together with that onto SOJR for comparison, which suggests that adsorption of Zr(IV) increased from 50.2% to 90.8% with increasing pH from 0.75 to 1.53 whereas more than 98% of was adsorbed at pH 2.2, from which the loading of Zr(IV) was decided to be carried out at pH around 2.2 for the preparation of Zr-ATOJR. Similarly, in the case of SOJR reported in the previous work [17], the adsorption of Zr(IV) was also increased from 78.5% to 97.3% by increasing pH from 0.74 to 1.56 and it was nearly 100% at around pH 2.2, which is exactly the similar trend with that of ATOJR. The nature of increasing adsorption of Zr(IV) with increasing pH in both gels suggests that adsorption of Zr(IV) onto these adsorbents takes place in the same manner of cation exchange mechanism between hydrogen ions of carboxylic groups of pectic acid contained in ATOJR and SOJR and cationic Zr(IV) ion as depicted by Figure 6.…”

“…Compared also with Zr-SOJR which uses the same feed material, orange juice residue (OJR), the maximum adsorption capacity on Zr-ATOJR (0.71 mmol/g) is lower than that on Zr-SOJR (1.20 mmol/g) at 303 K. This difference is attributable to the difference in the loading capacity for Zr(IV) between SOJR and ATOJR; i.e. that for SOJR is 1.62 mmol/g [17] while that for ATOJR is 0.83 mmol/g. This difference in the loading capacity is considered to be caused by the difference of the treatments for OJR; i.e.…”

“…In order to effectively use OJR as adsorbents for cationic metal ions, such methyl ester portion should be converted into carboxyl groups which exhibit high affinity for cationic metal ions. In our other previous work [17], we studied the adsorptive removal of some heavy metals such as lead (II) using OJR treated by the saponification reaction using calcium hydroxide, which is abbreviated as SOJR (Saponified Orange Juice Residue) hereafter. Furthermore, we also studied the adsorptive removal of trace concentrations of fluoride using SOJR loaded with high valent metal ions such as aluminum (III), tin (IV), lanthanum (III), titanium (IV) and zirconium (IV) [18,19].…”

Modelling lead(II) sorption to ferrihydrite and soil organic matter

“…Again Pb 2+ adsorption was underestimated 16 considerably, suggesting that the generic complexation constants, developed for dissolved 17 humic and fulvic acid, were not appropriate for solid-phase organic matter. 18 …”

“…It was therefore decided to merge these data sets 16 into one single data set with 65 data points collected at 8 different combinations of Pb 2+ 17 and ferrihydrite concentrations. 18 …”