<font-awesome-icon icon="fa-thin fa-9" />
<FontAwesomeIcon icon="fa-thin fa-9" />
.my-icon::before {
font: var(--fa-font-thin);
content: "\39";
}
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 320 512" style="width: 30px;height: 30px;fill: black">
<path d="M320 192c0-88.22-71.78-160-160-160s-160 71.78-160 160S71.78 352 160 352c20.99 0 40.94-4.311 59.33-11.7l-121.1 126.2c-3.062 3.188-2.938 8.25 .25 11.31C100 479.3 101.1 480 104 480c2.094 0 4.188-.8125 5.781-2.469C280.2 300 320 273.9 320 192zM16 192c0-79.41 64.59-144 144-144s144 64.59 144 144s-64.59 144-144 144S16 271.4 16 192z"/>
</svg>
<i class="fa-thin fa-9"></i>