The use of a polysaccharide extract isolated from cactus pads (Opuntia ficus indica) as a low-cost adsorbent for the removal of Pb 21 and Cd 21 from water was investigated. The Brunauer2Emmett2Teller study showed that the surface area of the extract powder was approximately 2.373 m 2 /g. Inductively coupled plasma optical emission spectrometry was used to monitor changes in ion concentrations during the adsorption. The adsorption mechanism was studied as a function of physicochemical variables such as initial metal ion concentration, adsorbent dosage, contact time, and pH of the solution. The results indicated that the adsorption percentage of the two cations increased with contact time, attaining equilibrium at 150 and 120 min for Cd 21 and Pb 21 , respectively. At these optimal times, the adsorption capacity of Pb 21 and Cd 21 increased with increasing pH. Langmuir, Freundlich, Toth, Dubinin-Radushkevich, Sips, and Redlich-Peterson isotherm models were thereafter applied to understand the adsorption mechanism. The qe plot against C e for the Toth isotherm model had the best fit with low error values and the highest correlation coefficient (R 2 ) values of 0.9973 and 0.9953 for Pb 21 and Cd 21 , respectively. Therefore, the isotherm study reveals that the adsorption mechanism involved is complex because of the presence of different interactions (such as ionic exchange and coagulation), yielding maximum adsorption capacities of 256 and 151 gm/L for Pb 21 and Cd 21 , respectively. Generally, the polysaccharide extract exhibited higher adsorption capacity of Pb 21 than of Cd 21 under similar conditions. Besides the removal capacities reported in this study, the adsorbent regeneration and its reusability was also investigated.

The degradation of Rhodamine B dye (RhB) by polysaccharide‐synthesized silver nanoparticles (PE‐AgNPs) has been studied by fluorescence excitation (λex) and emission (λem) matrices (FEEM) spectroscopy. This study reports the behavior of RhB under the influence of PE‐AgNPs using the FEEM technique. The observed 3D excitation and emission maps reveal that, at λex (400 nm)/λem (580 nm), fluorescence quenching occurs. The 3D maps/peaks show that this type of quenching occurs in the presence of PE‐AgNPs and is indicated by the decrease in the intensity of spectral peaks. At pH 8, the maximum quenching of these peaks occurrs. Further investigations show that temperature and contact time influence RhB quenching significantly. The trends observed shows that higher temperatures leads to reduction of RhB fluorescence intensity increases with increase in temperature and decrease with time. This study suggests that the fluorescence quenching of RhB, can be due to its adsorption on the conductive surface of PE‐AgNPs. The results presented in this study give experimental evidence and insights that PE‐mediated green synthesized AgNPs can be a promising RhB degrading agent. Besides, the interactions of RhB with PE‐AgNPs, can prevent leaching and thus minimize dye toxicity in water.