Fig. 4 shows plot of percentage P removal by the Al-WTR plotted
alongside P-uptake using 48-h equilibration time and P concentration
of 5 mg P L1. The figure shows percentage P removal
increased steadily with increase in adsorbent dosage up to 10 g L1
suggesting that phosphate adsorption onto Al-WTR depends on
availability of positively charged adsorption sites. Similar trend was
observed for all the initial P concentrations used and only the plot
of initial P concentration of 5 mg P L1 is shown to illustrate the
general trend. However, at dosages beyond 10 g L1, increase in P
removal (%) became marginal and P-uptake decreased with
increase in adsorbent dosage. This is consistent with the expectation
that higher adsorbent dosages will result in lower adsorption
efficiencies per gram, as the adsorbed phosphate is distributed
among more available binding sites.